From cd2b1f2dde3951cb5e065dd31adcc5d9b50fc03e Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Fri, 7 Feb 2020 19:48:34 -0600
Subject: [PATCH 01/36] Add code to support changing CPU frequency.

---
 .cproject                       |  32 +++---
 .settings/language.settings.xml |   4 +-
 Inc/main.h                      |  14 +++
 Src/main.c                      | 175 ++++++++++++++++++++++++++++++--
 4 files changed, 197 insertions(+), 28 deletions(-)

diff --git a/.cproject b/.cproject
index e1bda8d..a57d2b0 100644
--- a/.cproject
+++ b/.cproject
@@ -53,10 +53,10 @@
 							<option id="ilg.gnuarmeclipse.managedbuild.cross.option.optimization.other.1937611003" name="Other optimization flags" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.optimization.other" useByScannerDiscovery="true" value="-fstack-usage -fstrict-aliasing -ffast-math" valueType="string"/>
 							<option id="ilg.gnuarmeclipse.managedbuild.cross.option.optimization.noinlinefunctions.1239408347" name="Do not inline functions (-fno-inline-functions)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.optimization.noinlinefunctions" useByScannerDiscovery="true" value="true" valueType="boolean"/>
 							<targetPlatform archList="all" binaryParser="org.eclipse.cdt.core.ELF" id="ilg.gnuarmeclipse.managedbuild.cross.targetPlatform.555069223" isAbstract="false" osList="all" superClass="ilg.gnuarmeclipse.managedbuild.cross.targetPlatform"/>
-							<builder autoBuildTarget="all" buildPath="${workspace_loc:/TNC3-firmware}/ARM Debug" cleanBuildTarget="clean" command="${cross_make}" enableAutoBuild="true" id="org.eclipse.cdt.build.core.internal.builder.1584568207" incrementalBuildTarget="all" keepEnvironmentInBuildfile="false" managedBuildOn="true" name="CDT Internal Builder" parallelBuildOn="true" parallelizationNumber="optimal" superClass="org.eclipse.cdt.build.core.internal.builder"/>
+							<builder autoBuildTarget="all" buildPath="${workspace_loc:/TNC3-firmware}/ARM Debug" cleanBuildTarget="clean" command="${cross_make}" enableAutoBuild="true" id="org.eclipse.cdt.build.core.internal.builder.1584568207" incrementalBuildTarget="all" keepEnvironmentInBuildfile="false" managedBuildOn="true" name="CDT Internal Builder" parallelBuildOn="false" superClass="org.eclipse.cdt.build.core.internal.builder"/>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler.1401064567" name="GNU ARM Cross Assembler" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler">
 								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.usepreprocessor.33292167" name="Use preprocessor" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.usepreprocessor" useByScannerDiscovery="false" value="true" valueType="boolean"/>
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths.685185658" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths" useByScannerDiscovery="true" valueType="includePath">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths.685185658" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths" useByScannerDiscovery="true" valueType="includePath">
 									<listOptionValue builtIn="false" value="/usr/arm-none-eabi/include"/>
 									<listOptionValue builtIn="false" value="../Inc"/>
 									<listOptionValue builtIn="false" value="../Drivers/STM32L4xx_HAL_Driver/Inc"/>
@@ -69,7 +69,7 @@
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Inc/"/>
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Core/Inc"/>
 								</option>
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs.2108011045" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs.2108011045" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
 									<listOptionValue builtIn="false" value="__FPU_PRESENT=1"/>
 									<listOptionValue builtIn="false" value="USE_HAL_DRIVER"/>
 									<listOptionValue builtIn="false" value="ARM_MATH_CM4"/>
@@ -80,7 +80,7 @@
 								<inputType id="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler.input.820649784" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler.input"/>
 							</tool>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler.1175769653" name="GNU ARM Cross C Compiler" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler">
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths.377832116" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths.377832116" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
 									<listOptionValue builtIn="false" value="/usr/arm-none-eabi/include"/>
 									<listOptionValue builtIn="false" value="../Inc"/>
 									<listOptionValue builtIn="false" value="../Drivers/CMSIS/Include"/>
@@ -93,7 +93,7 @@
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Core/Inc"/>
 									<listOptionValue builtIn="false" value="../Drivers/STM32L4xx_HAL_Driver/Inc"/>
 								</option>
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs.2123477218" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs.2123477218" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
 									<listOptionValue builtIn="false" value="__FPU_PRESENT=1"/>
 									<listOptionValue builtIn="false" value="USE_HAL_DRIVER"/>
 									<listOptionValue builtIn="false" value="ARM_MATH_CM4"/>
@@ -107,7 +107,7 @@
 								<inputType id="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler.input.1359599970" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler.input"/>
 							</tool>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.compiler.1728068044" name="GNU ARM Cross C++ Compiler" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.compiler">
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths.1069495617" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths.1069495617" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
 									<listOptionValue builtIn="false" value="/usr/arm-none-eabi/include"/>
 									<listOptionValue builtIn="false" value="../Inc"/>
 									<listOptionValue builtIn="false" value="../Drivers/STM32L4xx_HAL_Driver/Inc"/>
@@ -121,7 +121,7 @@
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Core/Inc"/>
 									<listOptionValue builtIn="false" value="/usr/local/include"/>
 								</option>
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs.1120661678" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs.1120661678" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
 									<listOptionValue builtIn="false" value="__FPU_PRESENT=1"/>
 									<listOptionValue builtIn="false" value="USE_HAL_DRIVER"/>
 									<listOptionValue builtIn="false" value="ARM_MATH_CM4"/>
@@ -148,7 +148,7 @@
 							</tool>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.linker.1645159175" name="GNU ARM Cross C++ Linker" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.linker">
 								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.gcsections.1081471382" name="Remove unused sections (-Xlinker --gc-sections)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.gcsections" useByScannerDiscovery="false" value="true" valueType="boolean"/>
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile.675234327" name="Script files (-T)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile" useByScannerDiscovery="false" valueType="stringList">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile.675234327" name="Script files (-T)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile" useByScannerDiscovery="false" valueType="stringList">
 									<listOptionValue builtIn="false" value="&quot;${workspace_loc:/${ProjName}/STM32L433CCUx_FLASH.ld}&quot;"/>
 								</option>
 								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.nostdlibs.1855020595" name="No startup or default libs (-nostdlib)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.nostdlibs" useByScannerDiscovery="false" value="false" valueType="boolean"/>
@@ -194,7 +194,7 @@
 				</extensions>
 			</storageModule>
 			<storageModule moduleId="cdtBuildSystem" version="4.0.0">
-				<configuration artifactName="firmware" buildArtefactType="org.eclipse.cdt.build.core.buildArtefactType.exe" buildProperties="org.eclipse.cdt.build.core.buildArtefactType=org.eclipse.cdt.build.core.buildArtefactType.exe,org.eclipse.cdt.build.core.buildType=org.eclipse.cdt.build.core.buildType.debug" cleanCommand="${cross_rm} -rf" description="" id="ilg.gnuarmeclipse.managedbuild.cross.config.elf.debug.1309195742.6250637.815824991" name="ARM_Release" optionalBuildProperties="" parent="ilg.gnuarmeclipse.managedbuild.cross.config.elf.debug" postbuildStep="${cross_prefix}${cross_objcopy}${cross_suffix} firmware.elf -O binary firmware.bin">
+				<configuration artifactName="firmware" buildArtefactType="org.eclipse.cdt.build.core.buildArtefactType.exe" buildProperties="org.eclipse.cdt.build.core.buildArtefactType=org.eclipse.cdt.build.core.buildArtefactType.exe,org.eclipse.cdt.build.core.buildType=org.eclipse.cdt.build.core.buildType.debug" cleanCommand="${cross_rm} -rf" description="" id="ilg.gnuarmeclipse.managedbuild.cross.config.elf.debug.1309195742.6250637.815824991" name="ARM_Release" optionalBuildProperties="" parent="ilg.gnuarmeclipse.managedbuild.cross.config.elf.debug" postbuildStep="">
 					<folderInfo id="ilg.gnuarmeclipse.managedbuild.cross.config.elf.debug.1309195742.6250637.815824991." name="/" resourcePath="">
 						<toolChain id="ilg.gnuarmeclipse.managedbuild.cross.toolchain.elf.debug.74600812" name="ARM Cross GCC" nonInternalBuilderId="ilg.gnuarmeclipse.managedbuild.cross.builder" superClass="ilg.gnuarmeclipse.managedbuild.cross.toolchain.elf.debug">
 							<option id="ilg.gnuarmeclipse.managedbuild.cross.option.addtools.createflash.1538196244" name="Create flash image" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.addtools.createflash" useByScannerDiscovery="false" value="true" valueType="boolean"/>
@@ -238,7 +238,7 @@
 							<builder autoBuildTarget="all" buildPath="${workspace_loc:/TNC3-firmware}/ARM Debug" cleanBuildTarget="clean" command="${cross_make}" enableAutoBuild="true" id="org.eclipse.cdt.build.core.internal.builder.2110076473" incrementalBuildTarget="all" keepEnvironmentInBuildfile="false" managedBuildOn="true" name="CDT Internal Builder" parallelBuildOn="false" superClass="org.eclipse.cdt.build.core.internal.builder"/>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler.1093600654" name="GNU ARM Cross Assembler" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler">
 								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.usepreprocessor.1179297555" name="Use preprocessor" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.usepreprocessor" useByScannerDiscovery="false" value="true" valueType="boolean"/>
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths.1845769595" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths" useByScannerDiscovery="true" valueType="includePath">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths.1845769595" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths" useByScannerDiscovery="true" valueType="includePath">
 									<listOptionValue builtIn="false" value="/usr/arm-none-eabi/include"/>
 									<listOptionValue builtIn="false" value="../Drivers/STM32L4xx_HAL_Driver/Inc"/>
 									<listOptionValue builtIn="false" value="../Inc"/>
@@ -251,7 +251,7 @@
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Inc/"/>
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Core/Inc"/>
 								</option>
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs.208015513" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs.208015513" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
 									<listOptionValue builtIn="false" value="__FPU_PRESENT=1"/>
 									<listOptionValue builtIn="false" value="USE_HAL_DRIVER"/>
 									<listOptionValue builtIn="false" value="ARM_MATH_CM4"/>
@@ -261,7 +261,7 @@
 								<inputType id="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler.input.1462552668" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler.input"/>
 							</tool>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler.2037524494" name="GNU ARM Cross C Compiler" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler">
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths.549073773" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths.549073773" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
 									<listOptionValue builtIn="false" value="/usr/arm-none-eabi/include"/>
 									<listOptionValue builtIn="false" value="../Inc"/>
 									<listOptionValue builtIn="false" value="../Drivers/STM32L4xx_HAL_Driver/Inc"/>
@@ -274,7 +274,7 @@
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Inc/"/>
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Core/Inc"/>
 								</option>
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs.1057000273" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs.1057000273" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
 									<listOptionValue builtIn="false" value="__FPU_PRESENT=1"/>
 									<listOptionValue builtIn="false" value="USE_HAL_DRIVER"/>
 									<listOptionValue builtIn="false" value="ARM_MATH_CM4"/>
@@ -287,7 +287,7 @@
 								<inputType id="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler.input.1311038531" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler.input"/>
 							</tool>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.compiler.1738445104" name="GNU ARM Cross C++ Compiler" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.compiler">
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths.1151610661" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths.1151610661" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
 									<listOptionValue builtIn="false" value="/usr/arm-none-eabi/include"/>
 									<listOptionValue builtIn="false" value="/usr/local/include"/>
 									<listOptionValue builtIn="false" value="../Inc"/>
@@ -301,7 +301,7 @@
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Core/Inc"/>
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Inc/"/>
 								</option>
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs.602101294" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs.602101294" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
 									<listOptionValue builtIn="false" value="__FPU_PRESENT=1"/>
 									<listOptionValue builtIn="false" value="USE_HAL_DRIVER"/>
 									<listOptionValue builtIn="false" value="ARM_MATH_CM4"/>
@@ -327,7 +327,7 @@
 							</tool>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.linker.1881696985" name="GNU ARM Cross C++ Linker" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.linker">
 								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.gcsections.1261027452" name="Remove unused sections (-Xlinker --gc-sections)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.gcsections" useByScannerDiscovery="false" value="true" valueType="boolean"/>
-								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile.1929266642" name="Script files (-T)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile" useByScannerDiscovery="false" valueType="stringList">
+								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile.1929266642" name="Script files (-T)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile" useByScannerDiscovery="false" valueType="stringList">
 									<listOptionValue builtIn="false" value="&quot;${workspace_loc:/${ProjName}/STM32L433CCUx_FLASH.ld}&quot;"/>
 								</option>
 								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.nostdlibs.118214268" name="No startup or default libs (-nostdlib)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.nostdlibs" useByScannerDiscovery="false" value="false" valueType="boolean"/>
diff --git a/.settings/language.settings.xml b/.settings/language.settings.xml
index 2bda0b1..b29c417 100644
--- a/.settings/language.settings.xml
+++ b/.settings/language.settings.xml
@@ -3,7 +3,7 @@
 	<configuration id="ilg.gnuarmeclipse.managedbuild.cross.config.elf.debug.1309195742.6250637" name="ARM_Debug">
 		<extension point="org.eclipse.cdt.core.LanguageSettingsProvider">
 			<provider copy-of="extension" id="org.eclipse.cdt.ui.UserLanguageSettingsProvider"/>
-			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="-17584508179154847" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
+			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="793420653061" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
 				<language-scope id="org.eclipse.cdt.core.gcc"/>
 				<language-scope id="org.eclipse.cdt.core.g++"/>
 			</provider>
@@ -14,7 +14,7 @@
 	<configuration id="ilg.gnuarmeclipse.managedbuild.cross.config.elf.debug.1309195742.6250637.815824991" name="ARM_Release">
 		<extension point="org.eclipse.cdt.core.LanguageSettingsProvider">
 			<provider copy-of="extension" id="org.eclipse.cdt.ui.UserLanguageSettingsProvider"/>
-			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="39340766364977905" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
+			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="793420653061" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
 				<language-scope id="org.eclipse.cdt.core.gcc"/>
 				<language-scope id="org.eclipse.cdt.core.g++"/>
 			</provider>
diff --git a/Inc/main.h b/Inc/main.h
index 66e94aa..5cc3cf8 100644
--- a/Inc/main.h
+++ b/Inc/main.h
@@ -168,6 +168,20 @@ extern osMutexId hardwareInitMutexHandle;
 
 #define CxxErrorHandler() _Error_Handler(const_cast<char*>(__FILE__), __LINE__)
 
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+void SysClock48(void);
+void SysClock80(void);
+void SysClock4(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#define SystemClock_Config_48MHz SystemClock_Config
+
 /* USER CODE END Private defines */
 
 #ifdef __cplusplus
diff --git a/Src/main.c b/Src/main.c
index 5b65f58..749f553 100644
--- a/Src/main.c
+++ b/Src/main.c
@@ -705,12 +705,14 @@ void SystemClock_Config(void)
   RCC_OscInitStruct.LSEState = RCC_LSE_ON;
   RCC_OscInitStruct.LSIState = RCC_LSI_OFF;
   RCC_OscInitStruct.MSIState = RCC_MSI_ON;
-  RCC_OscInitStruct.MSICalibrationValue = 0;
+  RCC_OscInitStruct.HSIState = RCC_HSI_OFF;
+  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
+  RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
   RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
   RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
   RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
   RCC_OscInitStruct.PLL.PLLM = 1;
-  RCC_OscInitStruct.PLL.PLLN = 24;
+  RCC_OscInitStruct.PLL.PLLN = 40;
   RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV7;
   RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
   RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
@@ -719,7 +721,7 @@ void SystemClock_Config(void)
     _Error_Handler(__FILE__, __LINE__);
   }
 
-    /**Initializes the CPU, AHB and APB busses clocks 
+    /**Initializes the CPU, AHB and APB busses clocks
     */
   RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                               |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
@@ -738,7 +740,7 @@ void SystemClock_Config(void)
                               |RCC_PERIPHCLK_RNG|RCC_PERIPHCLK_ADC;
   PeriphClkInit.Usart3ClockSelection = RCC_USART3CLKSOURCE_PCLK1;
   PeriphClkInit.I2c1ClockSelection = RCC_I2C1CLKSOURCE_PCLK1;
-  PeriphClkInit.AdcClockSelection = RCC_ADCCLKSOURCE_PLLSAI1;
+  PeriphClkInit.AdcClockSelection = RCC_ADCCLKSOURCE_SYSCLK;
   PeriphClkInit.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;
   PeriphClkInit.UsbClockSelection = RCC_USBCLKSOURCE_PLLSAI1;
   PeriphClkInit.RngClockSelection = RCC_RNGCLKSOURCE_PLLSAI1;
@@ -758,30 +760,30 @@ void SystemClock_Config(void)
   HAL_RCCEx_EnableLSCO(RCC_LSCOSOURCE_LSE);
 #endif
 
-    /**Configure the main internal regulator output voltage 
+    /**Configure the main internal regulator output voltage
     */
   if (HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1) != HAL_OK)
   {
     _Error_Handler(__FILE__, __LINE__);
   }
 
-    /**Configure the Systick interrupt time 
+    /**Configure the Systick interrupt time
     */
   HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
 
-    /**Configure the Systick 
+    /**Configure the Systick
     */
   HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
 
-    /**Enable MSI Auto calibration 
+    /**Enable MSI Auto calibration
     */
   HAL_RCCEx_EnableMSIPLLMode();
 
-    /**Enable the SYSCFG APB clock 
+    /**Enable the SYSCFG APB clock
     */
   __HAL_RCC_CRS_CLK_ENABLE();
 
-    /**Configures CRS 
+    /**Configures CRS
     */
   RCC_CRSInitStruct.Prescaler = RCC_CRS_SYNC_DIV1;
   RCC_CRSInitStruct.Source = RCC_CRS_SYNC_SOURCE_LSE;
@@ -905,6 +907,7 @@ static void MX_I2C1_Init(void)
 {
 
   hi2c1.Instance = I2C1;
+//  hi2c1.Init.Timing = 0x00300F33;
   hi2c1.Init.Timing = 0x20000209;
   hi2c1.Init.OwnAddress1 = 0;
   hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
@@ -1434,6 +1437,158 @@ void init_rtc_alarm()
 
 }
 
+void SysClock48()
+{
+    RCC_OscInitTypeDef RCC_OscInitStruct;
+    RCC_ClkInitTypeDef RCC_ClkInitStruct;
+
+    if (HAL_RCC_GetHCLKFreq() == 48000000) return;
+
+    taskENTER_CRITICAL();
+
+    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
+                                |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
+    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
+    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
+    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
+    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
+
+    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
+    {
+      _Error_Handler(__FILE__, __LINE__);
+    }
+
+    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_LSI|RCC_OSCILLATORTYPE_LSE
+                                |RCC_OSCILLATORTYPE_MSI;
+    RCC_OscInitStruct.LSEState = RCC_LSE_ON;
+    RCC_OscInitStruct.LSIState = RCC_LSI_OFF;
+    RCC_OscInitStruct.MSIState = RCC_MSI_ON;
+    RCC_OscInitStruct.HSIState = RCC_HSI_OFF;
+    RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
+    RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
+    RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
+    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
+    RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
+    RCC_OscInitStruct.PLL.PLLM = 1;
+    RCC_OscInitStruct.PLL.PLLN = 24;
+    RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV7;
+    RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
+    RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
+    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
+    {
+      _Error_Handler(__FILE__, __LINE__);
+    }
+
+      /**Initializes the CPU, AHB and APB busses clocks
+      */
+    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
+                                |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
+    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
+    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
+    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
+    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
+
+    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
+    {
+      _Error_Handler(__FILE__, __LINE__);
+    }
+
+    /**Configure the Systick interrupt time
+    */
+    HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
+
+    taskEXIT_CRITICAL();
+}
+
+void SysClock80()
+{
+    RCC_OscInitTypeDef RCC_OscInitStruct;
+    RCC_ClkInitTypeDef RCC_ClkInitStruct;
+
+    if (HAL_RCC_GetHCLKFreq() == 80000000) return;
+
+    taskENTER_CRITICAL();
+
+    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
+                                |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
+    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
+    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
+    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
+    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
+
+    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
+    {
+      _Error_Handler(__FILE__, __LINE__);
+    }
+
+    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_LSI|RCC_OSCILLATORTYPE_LSE
+                                |RCC_OSCILLATORTYPE_MSI|RCC_OSCILLATORTYPE_HSI;
+    RCC_OscInitStruct.LSEState = RCC_LSE_ON;
+    RCC_OscInitStruct.LSIState = RCC_LSI_OFF;
+    RCC_OscInitStruct.MSIState = RCC_MSI_ON;
+    RCC_OscInitStruct.HSIState = RCC_HSI_OFF;
+    RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
+    RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
+    RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
+    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
+    RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
+    RCC_OscInitStruct.PLL.PLLM = 1;
+    RCC_OscInitStruct.PLL.PLLN = 40;
+    RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV7;
+    RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
+    RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
+    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
+    {
+      _Error_Handler(__FILE__, __LINE__);
+    }
+
+      /**Initializes the CPU, AHB and APB busses clocks
+      */
+    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
+                                |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
+    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
+    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
+    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
+    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
+
+    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)
+    {
+      _Error_Handler(__FILE__, __LINE__);
+    }
+
+    /**Configure the Systick interrupt time
+    */
+    HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
+
+    taskEXIT_CRITICAL();
+}
+
+void SysClock4()
+{
+    RCC_OscInitTypeDef RCC_OscInitStruct;
+    RCC_ClkInitTypeDef RCC_ClkInitStruct;
+
+    taskENTER_CRITICAL();
+
+    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
+                                |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
+    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
+    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
+    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
+    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
+
+    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
+    {
+      _Error_Handler(__FILE__, __LINE__);
+    }
+
+    /**Configure the Systick interrupt time
+    */
+    HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
+
+    taskEXIT_CRITICAL();
+}
+
 /* USER CODE END 4 */
 
 /* USER CODE BEGIN Header_StartDefaultTask */

From ef966e33067b3c2b1c48aa9fe631916330972d34 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Fri, 7 Feb 2020 19:51:44 -0600
Subject: [PATCH 02/36] Basic 9600 baud FSK support.

---
 TNC/AFSKModulator.hpp       |  56 +++++--
 TNC/Afsk1200Demodulator.cpp |  93 ++++++++++++
 TNC/Afsk1200Demodulator.hpp | 181 +++++++++++++++++++++++
 TNC/AfskDemodulator.hpp     |   3 +-
 TNC/AudioInput.cpp          | 284 +++++++++--------------------------
 TNC/AudioInput.hpp          |  18 ++-
 TNC/AudioLevel.cpp          |   4 +-
 TNC/AudioLevel.hpp          |   2 +-
 TNC/Demodulator.cpp         |  44 ++++++
 TNC/Demodulator.hpp         |  43 ++++++
 TNC/DigitalPLL.hpp          |  11 +-
 TNC/FilterCoefficients.cpp  |  35 +++++
 TNC/FilterCoefficients.hpp  |  22 +--
 TNC/FirFilter.hpp           |   1 -
 TNC/Fsk9600Demodulator.cpp  | 287 ++++++++++++++++++++++++++++++++++++
 TNC/Fsk9600Demodulator.hpp  | 107 ++++++++++++++
 TNC/Fsk9600Modulator.cpp    |  16 ++
 TNC/Fsk9600Modulator.hpp    | 216 +++++++++++++++++++++++++++
 TNC/Goertzel.h              | 150 ++++++++++---------
 TNC/HDLCEncoder.hpp         |   8 +-
 TNC/IOEventTask.cpp         |   4 +
 TNC/KissHardware.cpp        |  35 ++++-
 TNC/KissHardware.hpp        |   5 +-
 TNC/Modulator.hpp           |  93 ++++++++++++
 TNC/ModulatorTask.cpp       |  29 +++-
 TNC/ModulatorTask.hpp       |   8 +-
 stlink-tnc3.cfg             |   2 +-
 27 files changed, 1404 insertions(+), 353 deletions(-)
 create mode 100644 TNC/Afsk1200Demodulator.cpp
 create mode 100644 TNC/Afsk1200Demodulator.hpp
 create mode 100644 TNC/Demodulator.cpp
 create mode 100644 TNC/Demodulator.hpp
 create mode 100644 TNC/FilterCoefficients.cpp
 create mode 100644 TNC/Fsk9600Demodulator.cpp
 create mode 100644 TNC/Fsk9600Demodulator.hpp
 create mode 100644 TNC/Fsk9600Modulator.cpp
 create mode 100644 TNC/Fsk9600Modulator.hpp
 create mode 100644 TNC/Modulator.hpp

diff --git a/TNC/AFSKModulator.hpp b/TNC/AFSKModulator.hpp
index 7f31e04..e95456f 100644
--- a/TNC/AFSKModulator.hpp
+++ b/TNC/AFSKModulator.hpp
@@ -1,13 +1,13 @@
 // Copyright 2015-2019 Mobilinkd LLC <rob@mobilinkd.com>
 // All rights reserved.
 
-#ifndef MOBILINKD__TNC__AFSK_MODULATOR_HPP_
-#define MOBILINKD__TNC__AFSK_MODULATOR_HPP_
+#pragma once
 
 #include <stddef.h>
 
 #include "PTT.hpp"
 #include "Log.h"
+#include "Modulator.hpp"
 
 #include "stm32l4xx_hal.h"
 #include "cmsis_os.h"
@@ -62,8 +62,8 @@ const int16_t sin_table[SIN_TABLE_LEN] = {
 };
 
 
-struct AFSKModulator {
-
+struct AFSKModulator : Modulator
+{
     static const size_t DAC_BUFFER_LEN = 44;
     static const size_t BIT_LEN = DAC_BUFFER_LEN / 2;
     static const size_t MARK_SKIP = 12;
@@ -84,7 +84,24 @@ struct AFSKModulator {
             buffer_[i] = 2048;
     }
 
-    void set_volume(uint16_t v)
+   void init(const kiss::Hardware& hw) override
+   {
+       set_twist(hw.tx_twist);
+
+       // Configure 80MHz clock for 26.4ksps.
+       htim7.Init.Period = 3029;
+       if (HAL_TIM_Base_Init(&htim7) != HAL_OK)
+       {
+           ERROR("htim7 init failed");
+           CxxErrorHandler();
+       }
+   }
+
+   void deinit() override
+   {
+   }
+
+   void set_gain(uint16_t v) override
     {
         v = std::max<uint16_t>(256, v);
         v = std::min<uint16_t>(4096, v);
@@ -103,7 +120,8 @@ struct AFSKModulator {
 
     void set_twist(uint8_t twist) {twist_ = twist;}
 
-    void send(bool bit) {
+   void send(bool bit) override
+   {
         switch (running_) {
         case -1:
             fill_first(bit);
@@ -122,8 +140,10 @@ struct AFSKModulator {
         }
     }
 
-    void fill(uint16_t* buffer, bool bit) {
-        for (size_t i = 0; i != BIT_LEN; i++) {
+    void fill(uint16_t* buffer, bool bit)
+    {
+        for (size_t i = 0; i != BIT_LEN; i++)
+        {
             int s = sin_table[pos_];
             s -= 2048;
             s *= volume_;
@@ -149,15 +169,18 @@ struct AFSKModulator {
         }
     }
 
-    void fill_first(bool bit) {
+    void fill_first(bool bit) override
+    {
         fill(buffer_, bit);
     }
 
-    void fill_last(bool bit) {
+    void fill_last(bool bit) override
+    {
         fill(buffer_ + BIT_LEN, bit);
     }
 
-    void empty() {
+    void empty() override
+    {
         switch (running_) {
         case 1:
             running_ = 0;
@@ -174,7 +197,8 @@ struct AFSKModulator {
         }
     }
 
-    void abort() {
+    void abort() override
+    {
         running_ = -1;
         HAL_DAC_Stop_DMA(&hdac1, DAC_CHANNEL_1);
         HAL_TIM_Base_Stop(&htim7);
@@ -184,9 +208,11 @@ struct AFSKModulator {
         // Drain the queue.
         while (osMessageGet(dacOutputQueueHandle_, 0).status == osEventMessage);
     }
+
+   float bits_per_ms() const override
+   {
+       return 1.2f;
+   }
 };
 
 }} // mobilinkd::tnc
-
-
-#endif // MOBILINKD__TNC__AFSK_MODULATOR_HPP_
diff --git a/TNC/Afsk1200Demodulator.cpp b/TNC/Afsk1200Demodulator.cpp
new file mode 100644
index 0000000..f9fe4d0
--- /dev/null
+++ b/TNC/Afsk1200Demodulator.cpp
@@ -0,0 +1,93 @@
+// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
+// All rights reserved.
+
+#include "Afsk1200Demodulator.hpp"
+#include "Goertzel.h"
+#include "AudioInput.hpp"
+
+namespace mobilinkd { namespace tnc {
+
+afsk1200::emphasis_filter_type Afsk1200Demodulator::filter_1;
+afsk1200::emphasis_filter_type Afsk1200Demodulator::filter_2;
+afsk1200::emphasis_filter_type Afsk1200Demodulator::filter_3;
+
+afsk1200::Demodulator Afsk1200Demodulator::demod1(26400, Afsk1200Demodulator::filter_1);
+afsk1200::Demodulator Afsk1200Demodulator::demod2(26400, Afsk1200Demodulator::filter_2);
+afsk1200::Demodulator Afsk1200Demodulator::demod3(26400, Afsk1200Demodulator::filter_3);
+
+/*
+ * Return twist as a the difference in dB between mark and space.  The
+ * expected values are about 0dB for discriminator output and about 5.5dB
+ * for de-emphasized audio.
+ */
+float Afsk1200Demodulator::readTwist()
+{
+    DEBUG("enter Afsk1200Demodulator::readTwist");
+    constexpr uint32_t channel = AUDIO_IN;
+
+    float g1200 = 0.0f;
+    float g2200 = 0.0f;
+
+    GoertzelFilter<ADC_BLOCK_SIZE, SAMPLE_RATE> gf1200(1200.0, 0);
+    GoertzelFilter<ADC_BLOCK_SIZE, SAMPLE_RATE> gf2200(2200.0, 0);
+
+    const uint32_t AVG_SAMPLES = 20;
+
+    startADC(1817, ADC_BLOCK_SIZE);
+
+    for (uint32_t i = 0; i != AVG_SAMPLES; ++i)
+    {
+        uint32_t count = 0;
+        while (count < ADC_BLOCK_SIZE)
+        {
+            osEvent evt = osMessageGet(adcInputQueueHandle, osWaitForever);
+            if (evt.status != osEventMessage)
+                continue;
+
+            auto block = (audio::adc_pool_type::chunk_type*) evt.value.p;
+            uint16_t* data = (uint16_t*) block->buffer;
+            gf1200(data, ADC_BLOCK_SIZE);
+            gf2200(data, ADC_BLOCK_SIZE);
+
+            audio::adcPool.deallocate(block);
+
+            count += ADC_BLOCK_SIZE;
+        }
+
+        g1200 += (gf1200 / count);
+        g2200 += (gf2200 / count);
+
+        gf1200.reset();
+        gf2200.reset();
+    }
+
+    IDemodulator::stopADC();
+
+    g1200 = 10.0f * log10f(g1200 / AVG_SAMPLES);
+    g2200 = 10.0f * log10f(g2200 / AVG_SAMPLES);
+
+    auto result = g1200 - g2200;
+
+    INFO("Twist = %d / 100 (%d - %d)", int(result * 100), int(g1200),
+        int(g2200));
+
+    DEBUG("exit readTwist");
+    return result;
+}
+
+const q15_t Afsk1200Demodulator::bpf_coeffs[FILTER_TAP_NUM] = {
+    4,     0,    -5,   -10,   -13,   -12,    -9,    -4,    -2,    -4,   -12,   -26,
+  -41,   -52,   -51,   -35,    -3,    39,    83,   117,   131,   118,    83,    36,
+   -6,   -32,   -30,    -3,    36,    67,    66,    19,   -74,  -199,  -323,  -408,
+ -421,  -344,  -187,    17,   218,   364,   417,   369,   247,   106,    14,    26,
+  166,   407,   676,   865,   866,   605,    68,  -675, -1484, -2171, -2547, -2471,
+-1895,  -882,   394,  1692,  2747,  3337,  3337,  2747,  1692,   394,  -882, -1895,
+-2471, -2547, -2171, -1484,  -675,    68,   605,   866,   865,   676,   407,   166,
+   26,    14,   106,   247,   369,   417,   364,   218,    17,  -187,  -344,  -421,
+ -408,  -323,  -199,   -74,    19,    66,    67,    36,    -3,   -30,   -32,    -6,
+   36,    83,   118,   131,   117,    83,    39,    -3,   -35,   -51,   -52,   -41,
+  -26,   -12,    -4,    -2,    -4,    -9,   -12,   -13,   -10,    -5,     0,     4,
+};
+
+}} // mobilinkd::tnc
+
diff --git a/TNC/Afsk1200Demodulator.hpp b/TNC/Afsk1200Demodulator.hpp
new file mode 100644
index 0000000..7377099
--- /dev/null
+++ b/TNC/Afsk1200Demodulator.hpp
@@ -0,0 +1,181 @@
+// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
+// All rights reserved.
+
+#pragma once
+
+#include "Demodulator.hpp"
+#include "AfskDemodulator.hpp"
+#include "FirFilter.hpp"
+#include "FilterCoefficients.hpp"
+#include "KissHardware.hpp"
+#include "HdlcFrame.hpp"
+
+namespace mobilinkd { namespace tnc {
+
+struct Afsk1200Demodulator : IDemodulator
+{
+    /*
+     * Generated with Scipy Filter, 152 coefficients, 1100-2300Hz bandpass,
+     * Hann window, starting and ending 0 value coefficients removed.
+     *
+     * np.array(
+     *  firwin2(152,
+     *      [
+     *          0.0,
+     *          1000.0/(sample_rate/2),
+     *          1100.0/(sample_rate/2),
+     *          2350.0/(sample_rate/2),
+     *          2500.0/(sample_rate/2),
+     *          1.0
+     *      ],
+     *      [0,0,1,1,0,0],
+     *      antisymmetric = False,
+     *      window='hann') * 32768,
+     *  dtype=int)[10:-10]
+     */
+    static constexpr size_t FILTER_TAP_NUM = 132;
+    static constexpr uint32_t ADC_BLOCK_SIZE = afsk1200::ADC_BUFFER_SIZE;
+    static constexpr uint32_t SAMPLE_RATE = 26400;
+    static_assert(audio::ADC_BUFFER_SIZE >= ADC_BLOCK_SIZE);
+
+    using audio_filter_t = Q15FirFilter<ADC_BLOCK_SIZE, FILTER_TAP_NUM>;
+
+    static const q15_t bpf_coeffs[FILTER_TAP_NUM];
+
+
+    static afsk1200::emphasis_filter_type filter_1;
+    static afsk1200::emphasis_filter_type filter_2;
+    static afsk1200::emphasis_filter_type filter_3;
+
+    static afsk1200::Demodulator demod1;
+    static afsk1200::Demodulator demod2;
+    static afsk1200::Demodulator demod3;
+
+    audio_filter_t demod_filter;
+    uint16_t last_fcs{0};
+    uint32_t last_counter{0};
+    uint32_t counter{0};
+    bool locked_{false};
+
+    virtual ~Afsk1200Demodulator() {}
+
+    void start() override
+    {
+        INFO("Setting 48MHz SysClock.");
+        SysClock48();
+
+        // rx_twist is 6dB for discriminator input and 0db for de-emphasized input.
+        auto twist = kiss::settings().rx_twist;
+
+        filter_1.init(*filter::fir::AfskFilters[twist + 3]);
+        filter_2.init(*filter::fir::AfskFilters[twist + 6]);
+        filter_3.init(*filter::fir::AfskFilters[twist + 9]);
+
+        last_fcs = 0;
+        last_counter = 0;
+        counter = 0;
+
+        demod_filter.init(bpf_coeffs);
+
+        hadc1.Init.OversamplingMode = ENABLE;
+        if (HAL_ADC_Init(&hadc1) != HAL_OK)
+        {
+            CxxErrorHandler();
+        }
+
+        ADC_ChannelConfTypeDef sConfig;
+
+        sConfig.Channel = AUDIO_IN;
+        sConfig.Rank = ADC_REGULAR_RANK_1;
+        sConfig.SingleDiff = ADC_SINGLE_ENDED;
+        sConfig.SamplingTime = ADC_SAMPLETIME_12CYCLES_5;
+        sConfig.OffsetNumber = ADC_OFFSET_NONE;
+        sConfig.Offset = 0;
+        if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
+            CxxErrorHandler();
+
+        startADC(1817, ADC_BLOCK_SIZE);
+    }
+
+    void stop() override
+    {
+        stopADC();
+        locked_ = false;
+    }
+
+    hdlc::IoFrame* operator()(const q15_t* samples) override
+    {
+        hdlc::IoFrame* result = nullptr;
+
+        q15_t* filtered = demod_filter(const_cast<q15_t* >(samples));
+
+        ++counter;
+
+#if 1
+        auto frame1 = demod1(filtered, ADC_BLOCK_SIZE);
+        if (frame1)
+        {
+            if (frame1->fcs() != last_fcs or counter > last_counter + 2)
+            {
+                last_fcs = frame1->fcs();
+                last_counter = counter;
+                result = frame1;
+            }
+            else
+            {
+                hdlc::release (frame1);
+            }
+        }
+#endif
+
+#if 1
+        auto frame2 = demod2(filtered, ADC_BLOCK_SIZE);
+        if (frame2)
+        {
+            if (frame2->fcs() != last_fcs or counter > last_counter + 2)
+            {
+                last_fcs = frame2->fcs();
+                last_counter = counter;
+                result = frame2;
+            }
+            else
+            {
+                hdlc::release(frame2);
+            }
+        }
+#endif
+
+#if 1
+        auto frame3 = demod3(filtered, ADC_BLOCK_SIZE);
+        if (frame3)
+        {
+            if (frame3->fcs() != last_fcs or counter > last_counter + 2)
+            {
+                last_fcs = frame3->fcs();
+                last_counter = counter;
+                result = frame3;
+            }
+            else
+            {
+                hdlc::release(frame3);
+            }
+        }
+#endif
+        locked_ = demod1.locked() or demod2.locked() or demod3.locked();
+        return result;
+    }
+
+    float readTwist() override;
+
+    bool locked() const override
+    {
+        return locked_;
+    }
+
+    size_t size() const override
+    {
+        return ADC_BLOCK_SIZE;
+    }
+};
+
+}} // mobilinkd::tnc
diff --git a/TNC/AfskDemodulator.hpp b/TNC/AfskDemodulator.hpp
index a3411c0..4769417 100644
--- a/TNC/AfskDemodulator.hpp
+++ b/TNC/AfskDemodulator.hpp
@@ -31,7 +31,8 @@ const q15_t lpf_coeffs[] = {
    14,    18,    20,    19,    17,    14,    11,     8,     5,     3,     1,     0,
 };
 
-typedef FirFilter<audio::ADC_BUFFER_SIZE, 9> emphasis_filter_type;
+static constexpr uint32_t ADC_BUFFER_SIZE = 88;
+typedef FirFilter<ADC_BUFFER_SIZE, 9> emphasis_filter_type;
 
 struct Demodulator {
 
diff --git a/TNC/AudioInput.cpp b/TNC/AudioInput.cpp
index 2bde7e5..2bbe632 100644
--- a/TNC/AudioInput.cpp
+++ b/TNC/AudioInput.cpp
@@ -2,15 +2,13 @@
 // All rights reserved.
 
 #include "AudioInput.hpp"
-#include "AfskDemodulator.hpp"
+#include "Afsk1200Demodulator.hpp"
+#include "Fsk9600Demodulator.hpp"
 #include "AudioLevel.hpp"
 #include "Log.h"
 #include "KissHardware.hpp"
 #include "GPIO.hpp"
 #include "HdlcFrame.hpp"
-#include "memory.hpp"
-#include "IirFilter.hpp"
-#include "FilterCoefficients.hpp"
 #include "PortInterface.hpp"
 #include "Goertzel.h"
 #include "DCD.h"
@@ -28,18 +26,13 @@ extern osMessageQId ioEventQueueHandle;
 
 extern "C" void SystemClock_Config(void);
 
-// 1kB
-typedef mobilinkd::tnc::memory::Pool<
-    8, mobilinkd::tnc::audio::ADC_BUFFER_SIZE * 2> adc_pool_type;
-adc_pool_type adcPool;
-
 // DMA Conversion first half complete.
 extern "C" void HAL_ADC_ConvHalfCpltCallback(ADC_HandleTypeDef*) {
     using namespace mobilinkd::tnc::audio;
 
     auto block = adcPool.allocate();
     if (!block) return;
-    memmove(block->buffer, adc_buffer, ADC_BUFFER_SIZE * 2);
+    memmove(block->buffer, adc_buffer, dma_transfer_size);
     auto status = osMessagePut(adcInputQueueHandle, (uint32_t) block, 0);
     if (status != osOK) adcPool.deallocate(block);
 }
@@ -50,7 +43,7 @@ extern "C" void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef*) {
 
     auto block = adcPool.allocate();
     if (!block) return;
-    memmove(block->buffer, adc_buffer + DMA_TRANSFER_SIZE, ADC_BUFFER_SIZE * 2);
+    memmove(block->buffer, adc_buffer + half_buffer_size, dma_transfer_size);
     auto status = osMessagePut(adcInputQueueHandle, (uint32_t) block, 0);
     if (status != osOK) adcPool.deallocate(block);
 }
@@ -132,96 +125,47 @@ extern "C" void startAudioInputTask(void const*) {
 
 namespace mobilinkd { namespace tnc { namespace audio {
 
-/*
- * Generated with Scipy Filter, 152 coefficients, 1100-2300Hz bandpass,
- * Hann window, starting and ending 0 value coefficients removed.
- *
- * np.array(
- *  firwin2(152,
- *      [
- *          0.0,
- *          1000.0/(sample_rate/2),
- *          1100.0/(sample_rate/2),
- *          2350.0/(sample_rate/2),
- *          2500.0/(sample_rate/2),
- *          1.0
- *      ],
- *      [0,0,1,1,0,0],
- *      antisymmetric = False,
- *      window='hann') * 32768,
- *  dtype=int)[10:-10]
- */
-constexpr size_t FILTER_TAP_NUM = 132;
-const q15_t bpf_coeffs[] = {
-    4,     0,    -5,   -10,   -13,   -12,    -9,    -4,    -2,    -4,   -12,   -26,
-  -41,   -52,   -51,   -35,    -3,    39,    83,   117,   131,   118,    83,    36,
-   -6,   -32,   -30,    -3,    36,    67,    66,    19,   -74,  -199,  -323,  -408,
- -421,  -344,  -187,    17,   218,   364,   417,   369,   247,   106,    14,    26,
-  166,   407,   676,   865,   866,   605,    68,  -675, -1484, -2171, -2547, -2471,
--1895,  -882,   394,  1692,  2747,  3337,  3337,  2747,  1692,   394,  -882, -1895,
--2471, -2547, -2171, -1484,  -675,    68,   605,   866,   865,   676,   407,   166,
-   26,    14,   106,   247,   369,   417,   364,   218,    17,  -187,  -344,  -421,
- -408,  -323,  -199,   -74,    19,    66,    67,    36,    -3,   -30,   -32,    -6,
-   36,    83,   118,   131,   117,    83,    39,    -3,   -35,   -51,   -52,   -41,
-  -26,   -12,    -4,    -2,    -4,    -9,   -12,   -13,   -10,    -5,     0,     4,
-};
+uint32_t adc_buffer[ADC_BUFFER_SIZE];               // Two samples per element.
+uint32_t adc_block_size = ADC_BUFFER_SIZE;          // Based on demodulator.
+uint32_t dma_transfer_size = adc_block_size * 2;    // Transfer size in bytes.
+uint32_t half_buffer_size = adc_block_size / 2;     // Transfer size in words / 2.
+adc_pool_type adcPool;
 
-uint32_t adc_buffer[ADC_BUFFER_SIZE];       // Two samples per element.
-
-typedef Q15FirFilter<ADC_BUFFER_SIZE, FILTER_TAP_NUM> audio_filter_type;
-
-audio_filter_type audio_filter;
-
-mobilinkd::tnc::afsk1200::emphasis_filter_type filter_1;
-mobilinkd::tnc::afsk1200::emphasis_filter_type filter_2;
-mobilinkd::tnc::afsk1200::emphasis_filter_type filter_3;
-
-mobilinkd::tnc::afsk1200::Demodulator& getDemod1(const TFirCoefficients<9>& f) __attribute__((noinline));
-mobilinkd::tnc::afsk1200::Demodulator& getDemod2(const TFirCoefficients<9>& f) __attribute__((noinline));
-mobilinkd::tnc::afsk1200::Demodulator& getDemod3(const TFirCoefficients<9>& f) __attribute__((noinline));
-
-mobilinkd::tnc::afsk1200::Demodulator& getDemod1(const TFirCoefficients<9>& f) {
-    filter_1.init(f);
-    static mobilinkd::tnc::afsk1200::Demodulator instance(26400, filter_1);
-    return instance;
-}
-
-mobilinkd::tnc::afsk1200::Demodulator& getDemod2(const TFirCoefficients<9>& f) {
-    filter_2.init(f);
-    static mobilinkd::tnc::afsk1200::Demodulator instance(26400, filter_2);
-    return instance;
-}
-
-mobilinkd::tnc::afsk1200::Demodulator& getDemod3(const TFirCoefficients<9>& f) {
-    filter_3.init(f);
-    static mobilinkd::tnc::afsk1200::Demodulator instance(26400, filter_3);
-    return instance;
+void set_adc_block_size(uint32_t block_size)
+{
+    adc_block_size = block_size;
+    dma_transfer_size = block_size * 2;
+    half_buffer_size = block_size / 2;
 }
 
 q15_t normalized[ADC_BUFFER_SIZE];
 
+
+IDemodulator* getDemodulator()
+{
+    static Afsk1200Demodulator afsk1200;
+    static Fsk9600Demodulator fsk9600;
+
+    switch (kiss::settings().modem_type)
+    {
+    case kiss::Hardware::ModemType::AFSK1200:
+        return &afsk1200;
+    case kiss::Hardware::ModemType::FSK9600:
+        return &fsk9600;
+    default:
+        ERROR("Invalid demodulator");
+        CxxErrorHandler();
+    }
+}
+
 void demodulatorTask() {
 
     DEBUG("enter demodulatorTask");
 
-    audio_filter.init(bpf_coeffs);
-
-    // rx_twist is 6dB for discriminator input and 0db for de-emphasized input.
-    auto twist = kiss::settings().rx_twist;
-
-    mobilinkd::tnc::afsk1200::Demodulator& demod1 = getDemod1(*filter::fir::AfskFilters[twist + 3]);
-    mobilinkd::tnc::afsk1200::Demodulator& demod2 = getDemod2(*filter::fir::AfskFilters[twist + 6]);
-    mobilinkd::tnc::afsk1200::Demodulator& demod3 = getDemod3(*filter::fir::AfskFilters[twist + 9]);
-
-    startADC(AUDIO_IN);
-
-    mobilinkd::tnc::hdlc::IoFrame* frame = 0;
-
-    uint16_t last_fcs = 0;
-    uint32_t last_counter = 0;
-    uint32_t counter = 0;
-
     bool dcd_status{false};
+    auto demodulator = getDemodulator();
+
+    demodulator->start();
 
     while (true) {
         osEvent peek = osMessagePeek(audioInputQueueHandle, 0);
@@ -232,80 +176,36 @@ void demodulatorTask() {
             continue;
         }
 
-        ++counter;
+        gpio::BAT_DIVIDER::off();
 
         auto block = (adc_pool_type::chunk_type*) evt.value.p;
         auto samples = (int16_t*) block->buffer;
 
-        arm_offset_q15(samples, 0 - virtual_ground, normalized, ADC_BUFFER_SIZE);
+        arm_offset_q15(samples, 0 - virtual_ground, normalized, demodulator->size());
         adcPool.deallocate(block);
-        q15_t* audio = audio_filter(normalized);
 
-#if 1
-        frame = demod1(audio, ADC_BUFFER_SIZE);
-        if (frame) {
-            if (frame->fcs() != last_fcs or counter > last_counter + 2) {
-                auto save_fcs = frame->fcs();
-                if (osMessagePut(ioEventQueueHandle, (uint32_t) frame, 1) == osOK) {
-                  last_fcs = save_fcs;
-                  last_counter = counter;
-                } else {
-                  hdlc::release(frame);
-                }
-            }
-            else {
+        auto frame = (*demodulator)(normalized);
+        if (frame)
+        {
+            if (osMessagePut(ioEventQueueHandle, (uint32_t) frame, 1) != osOK)
+            {
                 hdlc::release(frame);
             }
         }
-#endif
 
-#if 1
-        frame = demod2(audio, ADC_BUFFER_SIZE);
-        if (frame) {
-          if (frame->fcs() != last_fcs or counter > last_counter + 2) {
-              auto save_fcs = frame->fcs();
-              if (osMessagePut(ioEventQueueHandle, (uint32_t) frame, 1) == osOK) {
-                last_fcs = save_fcs;
-                last_counter = counter;
-              } else {
-                hdlc::release(frame);
-              }
-          }
-          else {
-              hdlc::release(frame);
-          }
-        }
-#endif
-
-#if 1
-        frame = demod3(audio, ADC_BUFFER_SIZE);
-        if (frame) {
-          if (frame->fcs() != last_fcs or counter > last_counter + 2) {
-              auto save_fcs = frame->fcs();
-              if (osMessagePut(ioEventQueueHandle, (uint32_t) frame, 1) == osOK) {
-                last_fcs = save_fcs;
-                last_counter = counter;
-              } else {
-                hdlc::release(frame);
-              }
-          }
-          else {
-              hdlc::release(frame);
-          }
-        }
-#endif
-        bool new_dcd_status = demod1.locked() or demod2.locked() or demod3.locked();
-        if (new_dcd_status xor dcd_status) {
-            dcd_status = new_dcd_status;
+        if (demodulator->locked() xor dcd_status) {
+            dcd_status = demodulator->locked();
             if (dcd_status) {
                 dcd_on();
             } else {
                 dcd_off();
             }
         }
+        gpio::BAT_DIVIDER::on();
     }
 
-    stopADC();
+    demodulator->stop();
+
     dcd_off();
     DEBUG("exit demodulatorTask");
 }
@@ -317,7 +217,9 @@ void streamLevels(uint32_t channel, uint8_t cmd) {
 
     uint8_t data[9];
     INFO("streamLevels: start");
-    startADC(channel);
+
+    auto demodulator = getDemodulator();
+    demodulator->start();
 
     while (true) {
         osEvent peek = osMessagePeek(audioInputQueueHandle, 0);
@@ -328,15 +230,15 @@ void streamLevels(uint32_t channel, uint8_t cmd) {
         uint16_t vmin = std::numeric_limits<uint16_t>::max();
         uint16_t vmax = std::numeric_limits<uint16_t>::min();
 
-        while (count < 2640) {
+        while (count < demodulator->size() * 30) {
             osEvent evt = osMessageGet(adcInputQueueHandle, osWaitForever);
             if (evt.status != osEventMessage) continue;
 
-            count += ADC_BUFFER_SIZE;
+            count += demodulator->size();
 
             auto block = (adc_pool_type::chunk_type*) evt.value.p;
             auto start =  (uint16_t*) block->buffer;
-            auto end = start + ADC_BUFFER_SIZE;
+            auto end = start + demodulator->size();
 
             vmin = std::min(vmin, *std::min_element(start, end));
             vmax = std::max(vmax, *std::max_element(start, end));
@@ -363,46 +265,51 @@ void streamLevels(uint32_t channel, uint8_t cmd) {
         ioport->write(data, 9, 6, 10);
     }
 
-    stopADC();
+    demodulator->stop();
     DEBUG("exit streamLevels");
 }
 
-levels_type readLevels(uint32_t channel, uint32_t samples) {
+levels_type readLevels(uint32_t)
+{
 
     DEBUG("enter readLevels");
 
     // Return Vpp, Vavg, Vmin, Vmax as four 16-bit values, right justified.
 
-    uint16_t count = 0;
+    uint32_t BLOCKS = 30;
     uint32_t accum = 0;
+    uint32_t iaccum = 0;
     uint16_t vmin = std::numeric_limits<uint16_t>::max();
     uint16_t vmax = std::numeric_limits<uint16_t>::min();
 
     INFO("readLevels: start");
-    startADC(channel);
-
-    while (count < samples) {
+    auto demodulator = getDemodulator();
+    demodulator->start();
 
+    for (uint32_t count = 0; count != BLOCKS; ++count)
+    {
         osEvent evt = osMessageGet(adcInputQueueHandle, osWaitForever);
         if (evt.status != osEventMessage) continue;
 
         auto block = (adc_pool_type::chunk_type*) evt.value.p;
         auto start =  (uint16_t*) block->buffer;
-        auto end = start + ADC_BUFFER_SIZE;
+        auto end = start + demodulator->size();
 
         vmin = std::min(vmin, *std::min_element(start, end));
         vmax = std::max(vmax, *std::max_element(start, end));
         accum = std::accumulate(start, end, accum);
 
+        iaccum += (accum / demodulator->size());
+
         adcPool.deallocate(block);
 
-        count += ADC_BUFFER_SIZE;
+        accum = 0;
     }
 
-    stopADC();
+    demodulator->stop();
 
     uint16_t pp = vmax - vmin;
-    uint16_t avg = accum / count;
+    uint16_t avg = iaccum / BLOCKS;
     DEBUG("exit readLevels");
 
     return levels_type(pp, avg, vmin, vmax);
@@ -421,56 +328,7 @@ constexpr uint32_t TWIST_SAMPLE_SIZE = 88;
  */
 float readTwist()
 {
-
-  DEBUG("enter readTwist");
-  constexpr uint32_t channel = AUDIO_IN;
-
-  float g1200 = 0.0f;
-  float g2200 = 0.0f;
-
-  GoertzelFilter<TWIST_SAMPLE_SIZE, SAMPLE_RATE> gf1200(1200.0, 0);
-  GoertzelFilter<TWIST_SAMPLE_SIZE, SAMPLE_RATE> gf2200(2200.0, 0);
-
-  const uint32_t AVG_SAMPLES = 20;
-
-  startADC(channel);
-
-  for (uint32_t i = 0; i != AVG_SAMPLES; ++i)
-  {
-    uint32_t count = 0;
-    while (count < TWIST_SAMPLE_SIZE)
-    {
-        osEvent evt = osMessageGet(adcInputQueueHandle, osWaitForever);
-        if (evt.status != osEventMessage) continue;
-
-        auto block = (adc_pool_type::chunk_type*) evt.value.p;
-        uint16_t* data =  (uint16_t*) block->buffer;
-        gf1200(data, ADC_BUFFER_SIZE);
-        gf2200(data, ADC_BUFFER_SIZE);
-
-        adcPool.deallocate(block);
-
-        count += ADC_BUFFER_SIZE;
-    }
-
-    g1200 += (gf1200 / count);
-    g2200 += (gf2200 / count);
-
-    gf1200.reset();
-    gf2200.reset();
-  }
-
-  stopADC();
-
-  g1200 = 10.0f * log10f(g1200 / AVG_SAMPLES);
-  g2200 = 10.0f * log10f(g2200 / AVG_SAMPLES);
-
-  auto result = g1200 - g2200;
-
-  INFO("Twist = %d / 100 (%d - %d)", int(result*100), int(g1200), int(g2200));
-
-  DEBUG("exit readTwist");
-  return result;
+    return getDemodulator()->readTwist();
 }
 
 /*
@@ -507,7 +365,7 @@ void pollInputTwist()
 
     const uint32_t AVG_SAMPLES = 100;
 
-    startADC(channel);
+    IDemodulator::startADC(3029, TWIST_SAMPLE_SIZE);
 
     for (uint32_t i = 0; i != AVG_SAMPLES; ++i) {
 
@@ -534,7 +392,7 @@ void pollInputTwist()
       gf2200.reset();
     }
 
-    stopADC();
+    IDemodulator::stopADC();
 
     DEBUG("pollInputTwist: MARK=%d, SPACE=%d (x100)",
       int(g1200 * 100.0 / AVG_SAMPLES), int(g2200 * 100.0 / AVG_SAMPLES));
diff --git a/TNC/AudioInput.hpp b/TNC/AudioInput.hpp
index 7b186b3..5ede020 100644
--- a/TNC/AudioInput.hpp
+++ b/TNC/AudioInput.hpp
@@ -4,6 +4,8 @@
 #ifndef MOBILINKD__TNC__AUDIO__INPUT_HPP_
 #define MOBILINKD__TNC__AUDIO__INPUT_HPP_
 
+#include "memory.hpp"
+
 #include "main.h"
 #include "stm32l4xx_hal.h"
 #include "cmsis_os.h"
@@ -83,10 +85,19 @@ enum AdcState {
     STREAM_INSTANT_TWIST_LEVEL
 };
 
-const size_t ADC_BUFFER_SIZE = 88;
-const size_t DMA_TRANSFER_SIZE = ADC_BUFFER_SIZE / 2;
+const size_t ADC_BUFFER_SIZE = 384;
 extern uint32_t adc_buffer[];       // Two int16_t samples per element.
+extern uint32_t adc_block_size;
+extern uint32_t dma_transfer_size;
+extern uint32_t half_buffer_size;
 
+// 1kB
+typedef memory::Pool<8, ADC_BUFFER_SIZE * 2> adc_pool_type;
+extern adc_pool_type adcPool;
+
+void set_adc_block_size(uint32_t block_size);
+
+#if 0
 inline void stopADC() {
     if (HAL_ADC_Stop_DMA(&hadc1) != HAL_OK)
         CxxErrorHandler();
@@ -118,10 +129,11 @@ inline void restartADC() {
     if (HAL_ADC_Start_DMA(&hadc1, adc_buffer, ADC_BUFFER_SIZE * 2) != HAL_OK)
         CxxErrorHandler();
 }
+#endif
 
 /// Vpp, Vavg, Vmin, Vmax
 typedef std::tuple<uint16_t, uint16_t, uint16_t, uint16_t> levels_type;
-levels_type readLevels(uint32_t channel, uint32_t samples = 2640);
+levels_type readLevels(uint32_t channel);
 float readTwist();
 
 void demodulatorTask();
diff --git a/TNC/AudioLevel.cpp b/TNC/AudioLevel.cpp
index ea7f3f4..096fb25 100644
--- a/TNC/AudioLevel.cpp
+++ b/TNC/AudioLevel.cpp
@@ -13,6 +13,8 @@
 #include "stm32l4xx_hal.h"
 
 #include <algorithm>
+#include <tuple>
+#include <array>
 #include <cstdlib>
 #include <cstdint>
 
@@ -199,7 +201,7 @@ void setAudioOutputLevel()
   } else {
       gpio::AUDIO_OUT_ATTEN::off();
   }
-  getModulator().set_volume(r);
+  getModulator().set_gain(r);
 }
 
 }}} // mobilinkd::tnc::audio
diff --git a/TNC/AudioLevel.hpp b/TNC/AudioLevel.hpp
index 1b0aeaa..6f7533d 100644
--- a/TNC/AudioLevel.hpp
+++ b/TNC/AudioLevel.hpp
@@ -28,7 +28,7 @@ void setAudioInputLevels();
 void setAudioOutputLevel();
 
 extern bool streamInputDCOffset;
-constexpr const uint16_t vref = 16383; // Must match ADC output (adjust when oversampling)
+constexpr const uint16_t vref = 4095; // Must match ADC output (adjust when oversampling)
 extern uint16_t virtual_ground;
 extern float i_vgnd;
 
diff --git a/TNC/Demodulator.cpp b/TNC/Demodulator.cpp
new file mode 100644
index 0000000..7fffc5e
--- /dev/null
+++ b/TNC/Demodulator.cpp
@@ -0,0 +1,44 @@
+// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
+// All rights reserved.
+
+#include "Demodulator.hpp"
+
+namespace mobilinkd { namespace tnc {
+
+/**
+ * Start the ADC DMA transfer.  The block size is equal to the number of
+ * 32-bit elements in the buffer.  This is also equal to the number of
+ * 16-bit elements in each DMA "half complete" transfer.  Each DMA transfer
+ * results in block_size * 2 bytes being transferred.
+ *
+ * We must bear in mind that the DMA buffer size is expressed in DWORDs,
+ * the DMA transfer size is expressed in WORDs, and the memory copy operation
+ * in BYTEs.
+ *
+ * @param period
+ * @param block_size
+ */
+void IDemodulator::startADC(uint32_t period, uint32_t block_size)
+{
+    audio::set_adc_block_size(block_size);
+
+    htim6.Init.Period = period;
+    htim6.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
+    if (HAL_TIM_Base_Init(&htim6) != HAL_OK)
+    {
+        CxxErrorHandler();
+    }
+
+    if (HAL_TIM_Base_Start(&htim6) != HAL_OK)
+    {
+        CxxErrorHandler();
+    }
+
+    if (HAL_ADC_Start_DMA(&hadc1, audio::adc_buffer,
+        block_size * 2) != HAL_OK)
+    {
+        CxxErrorHandler();
+    }
+}
+
+}} // mobilinkd::tnc
diff --git a/TNC/Demodulator.hpp b/TNC/Demodulator.hpp
new file mode 100644
index 0000000..9eb2b3c
--- /dev/null
+++ b/TNC/Demodulator.hpp
@@ -0,0 +1,43 @@
+// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
+// All rights reserved.
+
+#pragma once
+
+#include "HdlcFrame.hpp"
+#include "FirFilter.hpp"
+#include "AudioInput.hpp"
+
+#include <functional>
+
+#include <arm_math.h>
+
+namespace mobilinkd { namespace tnc {
+
+constexpr size_t FILTER_TAP_NUM = 132;
+
+using demod_filter_t = std::function<q15_t*(q15_t*, size_t)>;
+using demodulator_t = std::function<hdlc::IoFrame*(q15_t*)>;
+
+struct IDemodulator
+{
+    virtual void start() = 0;
+    virtual void stop() = 0;
+    virtual hdlc::IoFrame* operator()(const q15_t* samples) = 0;
+    virtual float readTwist() = 0;
+
+    virtual bool locked() const = 0;
+    virtual size_t size() const = 0;
+
+    virtual ~IDemodulator() {}
+
+    static void startADC(uint32_t period, uint32_t block_size);
+
+    static void stopADC() {
+        if (HAL_ADC_Stop_DMA(&hadc1) != HAL_OK)
+            CxxErrorHandler();
+        if (HAL_TIM_Base_Stop(&htim6) != HAL_OK)
+            CxxErrorHandler();
+    }
+};
+
+}} // mobilinkd::tnc
diff --git a/TNC/DigitalPLL.hpp b/TNC/DigitalPLL.hpp
index 802dd28..13a73a9 100644
--- a/TNC/DigitalPLL.hpp
+++ b/TNC/DigitalPLL.hpp
@@ -29,10 +29,10 @@ struct PLLResult {
 // scipy.signal:
 //      b, a = bessel(4, [80.0/(1200/2)], 'lowpass')
 //
-const std::array<float, 5> lock_b = {
+constexpr std::array<float, 5> lock_b = {
     1.077063e-03,4.308253e-03,6.462379e-03,4.308253e-03,1.077063e-03,
 };
-const std::array<float, 5> lock_a = {
+constexpr std::array<float, 5> lock_a = {
     1.000000e+00,-2.774567e+00,2.962960e+00,-1.437990e+00,2.668296e-01,
 };
 
@@ -41,9 +41,10 @@ const std::array<float, 5> lock_a = {
 //      loop_coeffs = firwin(9, [64.0/(1200/2)], width = None,
 //          pass_zero = True, scale = True, window='hann')
 //
-const std::array<float, 7> loop_coeffs = {
+constexpr std::array<float, 7> loop_coeffs = {
 //     0.08160962754214955, 0.25029850550446403, 0.3361837339067726, 0.2502985055044641, 0.08160962754214969
-    3.196252e-02,1.204223e-01,2.176819e-01,2.598666e-01,2.176819e-01,1.204223e-01,3.196252e-02
+//    3.196252e-02,1.204223e-01,2.176819e-01,2.598666e-01,2.176819e-01,1.204223e-01,3.196252e-02
+    0.0, 0.0, 0.5, 0.5, 0.0, 0.0, 0.0
 };
 
 } // pll
@@ -59,7 +60,7 @@ struct BaseDigitalPLL
 	float_type sps_; 			///< Samples per symbol
 	float_type limit_;			///< Samples per symbol / 2
 	libafsk::BaseHysteresis<float_type> lock_;
-    FirFilter<1, 7> loop_filter_{pll::loop_coeffs.begin()};
+    FirFilter<1, pll::loop_coeffs.size()> loop_filter_{pll::loop_coeffs.begin()};
     IirFilter<5> lock_filter_{pll::lock_b, pll::lock_a};
 
 	bool last_;
diff --git a/TNC/FilterCoefficients.cpp b/TNC/FilterCoefficients.cpp
new file mode 100644
index 0000000..d335794
--- /dev/null
+++ b/TNC/FilterCoefficients.cpp
@@ -0,0 +1,35 @@
+// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
+// All rights reserved.
+
+#include "FilterCoefficients.hpp"
+
+namespace mobilinkd { namespace tnc { namespace filter {
+
+namespace fir {
+
+const TFirCoefficients<9>* AfskFilters[19] = {
+  &dB_6,
+  &dB_5,
+  &dB_4,
+  &dB_3,
+  &dB_2,
+  &dB_1,
+  &dB0,
+  &dB1,
+  &dB2,
+  &dB3,
+  &dB4,
+  &dB5,
+  &dB6,
+  &dB7,
+  &dB8,
+  &dB9,
+  &dB10,
+  &dB11,
+  &dB12
+};
+
+} // fir
+
+
+}}} // mobilinkd::tnc::filter
diff --git a/TNC/FilterCoefficients.hpp b/TNC/FilterCoefficients.hpp
index 5711dfc..f422526 100644
--- a/TNC/FilterCoefficients.hpp
+++ b/TNC/FilterCoefficients.hpp
@@ -297,27 +297,7 @@ const TFirCoefficients<9> dB_6 = {
     }
 };
 
-const TFirCoefficients<9>* AfskFilters[] = {
-  &dB_6,
-  &dB_5,
-  &dB_4,
-  &dB_3,
-  &dB_2,
-  &dB_1,
-  &dB0,
-  &dB1,
-  &dB2,
-  &dB3,
-  &dB4,
-  &dB5,
-  &dB6,
-  &dB7,
-  &dB8,
-  &dB9,
-  &dB10,
-  &dB11,
-  &dB12
-};
+extern const TFirCoefficients<9>* AfskFilters[19];
 
 } // fir
 
diff --git a/TNC/FirFilter.hpp b/TNC/FirFilter.hpp
index b679ee7..5ec221d 100644
--- a/TNC/FirFilter.hpp
+++ b/TNC/FirFilter.hpp
@@ -96,7 +96,6 @@ template <size_t BLOCK_SIZE, size_t FILTER_SIZE>
 struct Q15FirFilter {
     const q15_t* filter_taps{nullptr};
     q15_t filter_state[BLOCK_SIZE + FILTER_SIZE - 1];
-    q15_t filter_input[BLOCK_SIZE];
     q15_t filter_output[BLOCK_SIZE];
     q15_t vgnd_{0};
     q15_t i_vgnd_{0};
diff --git a/TNC/Fsk9600Demodulator.cpp b/TNC/Fsk9600Demodulator.cpp
new file mode 100644
index 0000000..2c94cc6
--- /dev/null
+++ b/TNC/Fsk9600Demodulator.cpp
@@ -0,0 +1,287 @@
+// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
+// All rights reserved.
+
+#include "Fsk9600Demodulator.hpp"
+#include "Goertzel.h"
+#include "AudioInput.hpp"
+
+namespace mobilinkd { namespace tnc {
+
+hdlc::IoFrame* Fsk9600Demodulator::operator()(const q15_t* samples)
+{
+    hdlc::IoFrame* result = nullptr;
+
+    auto filtered = demod_filter(const_cast<q15_t* >(samples));
+
+    for (size_t i = 0; i != ADC_BLOCK_SIZE; ++i)
+    {
+        auto sample = filtered[i];
+
+        bool bit = sample >= 0;
+        auto pll = pll_(bit);
+
+        if (pll.sample)
+        {
+            locked_ = pll.locked;
+
+            // We will only ever get one frame because there are
+            // not enough bits in a block for more than one.
+            if (result) {
+                auto tmp = hdlc_decoder_(nrzi_.decode(lfsr_(bit)), locked_);
+                if (tmp) hdlc::release(tmp);
+            } else {
+                result = hdlc_decoder_(nrzi_.decode(lfsr_(bit)), locked_);
+            }
+        }
+    }
+    return result;
+}
+
+/*
+ * Return twist as a the difference in dB between mark and space.  The
+ * expected values are about 0dB for discriminator output and about 5.5dB
+ * for de-emphasized audio.
+ */
+float Fsk9600Demodulator::readTwist()
+{
+    DEBUG("enter Fsk9600Demodulator::readTwist");
+    constexpr uint32_t channel = AUDIO_IN;
+
+    float g120 = 0.0f;
+    float g4800 = 0.0f;
+
+    GoertzelFilter<ADC_BLOCK_SIZE, SAMPLE_RATE> gf120(120.0, 0);
+    GoertzelFilter<ADC_BLOCK_SIZE, SAMPLE_RATE> gf4800(4800.0, 0);
+
+    const uint32_t AVG_SAMPLES = 160;
+
+    startADC(416, ADC_BLOCK_SIZE);
+
+    for (uint32_t i = 0; i != AVG_SAMPLES; ++i)
+    {
+        uint32_t count = 0;
+        while (count < ADC_BLOCK_SIZE)
+        {
+            osEvent evt = osMessageGet(adcInputQueueHandle, osWaitForever);
+            if (evt.status != osEventMessage)
+                continue;
+
+            auto block = (audio::adc_pool_type::chunk_type*) evt.value.p;
+            uint16_t* data = (uint16_t*) block->buffer;
+            gf120(data, ADC_BLOCK_SIZE);
+            gf4800(data, ADC_BLOCK_SIZE);
+
+            audio::adcPool.deallocate(block);
+
+            count += ADC_BLOCK_SIZE;
+        }
+
+        g120 += (gf120 / count);
+        g4800 += (gf4800 / count);
+
+        gf120.reset();
+        gf4800.reset();
+    }
+
+    IDemodulator::stopADC();
+
+    g120 = 10.0f * log10f(g120 / AVG_SAMPLES);
+    g4800 = 10.0f * log10f(g4800 / AVG_SAMPLES);
+
+    auto result = g120 - g4800;
+
+    INFO("9600 Twist = %d / 100 (%d - %d)", int(result * 100), int(g120 * 100),
+        int(g4800 * 100));
+
+    DEBUG("exit Fsk9600Demodulator::readTwist");
+    return result;
+}
+
+
+const Fsk9600Demodulator::bpf_bank_type Fsk9600Demodulator::bpf_bank = {{
+    // -3dB
+    {{
+            1,     0,     0,     0,     0,     0,    -1,    -1,    -1,    -1,     0,     0,
+            0,     0,     1,     2,     2,     3,     2,     2,     0,     0,    -2,    -3,
+           -4,    -4,    -3,    -1,     3,     9,    17,    27,    38,    48,    58,    65,
+           68,    67,    60,    46,    25,    -1,   -32,   -67,  -102,  -135,  -160,  -175,
+         -174,  -153,  -110,   -41,    54,   178,   327,   500,   692,   897,  1109,  1318,
+         1518,  1700,  1857,  1981,  2067,  2110,  2110,  2067,  1981,  1857,  1700,  1518,
+         1318,  1109,   897,   692,   500,   327,   178,    54,   -41,  -110,  -153,  -174,
+         -175,  -160,  -135,  -102,   -67,   -32,    -1,    25,    46,    60,    67,    68,
+           65,    58,    48,    38,    27,    17,     9,     3,    -1,    -3,    -4,    -4,
+           -3,    -2,     0,     0,     2,     2,     3,     2,     2,     1,     0,     0,
+            0,     0,    -1,    -1,    -1,    -1,     0,     0,     0,     0,     0,     1
+    }},
+    // -2dB
+    {{
+            1,     0,     0,     0,     0,    -1,    -1,    -1,    -1,    -1,    -1,    -1,
+            0,     0,     1,     1,     2,     2,     1,     0,     0,    -1,    -3,    -5,
+           -6,    -6,    -5,    -1,     3,    10,    20,    31,    42,    54,    64,    72,
+           75,    72,    63,    46,    21,   -11,   -49,   -92,  -135,  -175,  -208,  -229,
+         -233,  -216,  -173,  -102,     0,   131,   293,   481,   691,   915,  1147,  1378,
+         1598,  1799,  1971,  2108,  2203,  2251,  2251,  2203,  2108,  1971,  1799,  1598,
+         1378,  1147,   915,   691,   481,   293,   131,     0,  -102,  -173,  -216,  -233,
+         -229,  -208,  -175,  -135,   -92,   -49,   -11,    21,    46,    63,    72,    75,
+           72,    64,    54,    42,    31,    20,    10,     3,    -1,    -5,    -6,    -6,
+           -5,    -3,    -1,     0,     0,     1,     2,     2,     1,     1,     0,     0,
+           -1,    -1,    -1,    -1,    -1,    -1,    -1,     0,     0,     0,     0,     1
+    }},
+    // -1dB
+    {{
+            1,     0,     0,     0,     0,    -1,    -1,    -2,    -2,    -2,    -2,    -1,
+           -1,     0,     0,     0,     1,     1,     0,     0,    -1,    -3,    -5,    -7,
+           -8,    -8,    -6,    -2,     3,    11,    22,    34,    48,    60,    72,    80,
+           82,    78,    66,    45,    15,   -22,   -68,  -119,  -171,  -221,  -262,  -291,
+         -300,  -286,  -244,  -170,   -62,    79,   255,   460,   689,   936,  1191,  1445,
+         1688,  1909,  2100,  2251,  2356,  2410,  2410,  2356,  2251,  2100,  1909,  1688,
+         1445,  1191,   936,   689,   460,   255,    79,   -62,  -170,  -244,  -286,  -300,
+         -291,  -262,  -221,  -171,  -119,   -68,   -22,    15,    45,    66,    78,    82,
+           80,    72,    60,    48,    34,    22,    11,     3,    -2,    -6,    -8,    -8,
+           -7,    -5,    -3,    -1,     0,     0,     1,     1,     0,     0,     0,    -1,
+           -1,    -2,    -2,    -2,    -2,    -1,    -1,     0,     0,     0,     0,     1
+    }},
+    // 0dB
+    {{
+            1,     0,     0,     0,    -1,    -1,    -2,    -2,    -3,    -3,    -3,    -2,
+           -2,    -1,     0,     0,     0,     0,     0,    -1,    -3,    -5,    -7,    -9,
+          -10,   -10,    -7,    -3,     3,    13,    25,    39,    53,    68,    80,    88,
+           91,    85,    70,    45,     9,   -35,   -90,  -150,  -212,  -272,  -323,  -359,
+         -376,  -366,  -324,  -247,  -132,    21,   212,   436,   688,   959,  1240,  1520,
+         1789,  2034,  2244,  2412,  2528,  2587,  2587,  2528,  2412,  2244,  2034,  1789,
+         1520,  1240,   959,   688,   436,   212,    21,  -132,  -247,  -324,  -366,  -376,
+         -359,  -323,  -272,  -212,  -150,   -90,   -35,     9,    45,    70,    85,    91,
+           88,    80,    68,    53,    39,    25,    13,     3,    -3,    -7,   -10,   -10,
+           -9,    -7,    -5,    -3,    -1,     0,     0,     0,     0,     0,    -1,    -2,
+           -2,    -3,    -3,    -3,    -2,    -2,    -1,    -1,     0,     0,     0,     1
+    }},
+    // 1dB
+    {{
+            1,     1,     0,     0,    -1,    -2,    -2,    -3,    -3,    -4,    -4,    -3,
+           -3,    -2,    -1,    -1,    -1,    -1,    -1,    -3,    -5,    -7,    -9,   -11,
+          -12,   -12,    -9,    -4,     3,    14,    28,    43,    60,    76,    89,    98,
+          100,    93,    75,    45,     3,   -50,  -114,  -185,  -258,  -329,  -390,  -437,
+         -460,  -454,  -413,  -333,  -209,   -43,   164,   409,   686,   984,  1295,  1604,
+         1901,  2173,  2406,  2592,  2721,  2786,  2786,  2721,  2592,  2406,  2173,  1901,
+         1604,  1295,   984,   686,   409,   164,   -43,  -209,  -333,  -413,  -454,  -460,
+         -437,  -390,  -329,  -258,  -185,  -114,   -50,     3,    45,    75,    93,   100,
+           98,    89,    76,    60,    43,    28,    14,     3,    -4,    -9,   -12,   -12,
+          -11,    -9,    -7,    -5,    -3,    -1,    -1,    -1,    -1,    -1,    -2,    -3,
+           -3,    -4,    -4,    -3,    -3,    -2,    -2,    -1,     0,     0,     1,     1
+    }},
+    // 2dB
+    {{
+            1,     1,     0,     0,    -1,    -2,    -3,    -4,    -4,    -5,    -5,    -4,
+           -4,    -3,    -3,    -2,    -2,    -2,    -3,    -5,    -7,    -9,   -12,   -14,
+          -15,   -14,   -11,    -5,     3,    15,    31,    49,    67,    85,   100,   109,
+          110,   101,    80,    45,    -3,   -66,  -141,  -223,  -309,  -393,  -467,  -523,
+         -555,  -554,  -513,  -429,  -297,  -116,   110,   379,   684,  1013,  1356,  1699,
+         2028,  2329,  2588,  2794,  2937,  3010,  3010,  2937,  2794,  2588,  2329,  2028,
+         1699,  1356,  1013,   684,   379,   110,  -116,  -297,  -429,  -513,  -554,  -555,
+         -523,  -467,  -393,  -309,  -223,  -141,   -66,    -3,    45,    80,   101,   110,
+          109,   100,    85,    67,    49,    31,    15,     3,    -5,   -11,   -14,   -15,
+          -14,   -12,    -9,    -7,    -5,    -3,    -2,    -2,    -2,    -3,    -3,    -4,
+           -4,    -5,    -5,    -4,    -4,    -3,    -2,    -1,     0,     0,     1,     1
+    }},
+    // 3dB
+    {{
+            2,     1,     0,     0,    -1,    -3,    -4,    -4,    -5,    -6,    -6,    -5,
+           -5,    -4,    -4,    -3,    -3,    -4,    -5,    -7,    -9,   -12,   -15,   -17,
+          -18,   -17,   -13,    -6,     3,    17,    35,    55,    75,    95,   111,   121,
+          122,   111,    86,    45,   -12,   -85,  -171,  -267,  -367,  -465,  -552,  -620,
+         -661,  -665,  -626,  -537,  -395,  -199,    49,   346,   681,  1045,  1425,  1805,
+         2170,  2504,  2792,  3021,  3179,  3261,  3261,  3179,  3021,  2792,  2504,  2170,
+         1805,  1425,  1045,   681,   346,    49,  -199,  -395,  -537,  -626,  -665,  -661,
+         -620,  -552,  -465,  -367,  -267,  -171,   -85,   -12,    45,    86,   111,   122,
+          121,   111,    95,    75,    55,    35,    17,     3,    -6,   -13,   -17,   -18,
+          -17,   -15,   -12,    -9,    -7,    -5,    -4,    -3,    -3,    -4,    -4,    -5,
+           -5,    -6,    -6,    -5,    -4,    -4,    -3,    -1,     0,     0,     1,     2
+    }},
+    // 4dB
+    {{
+            2,     1,     0,    -1,    -2,    -3,    -4,    -5,    -6,    -7,    -7,    -7,
+           -6,    -6,    -5,    -5,    -5,    -6,    -7,    -9,   -12,   -15,   -18,   -20,
+          -21,   -20,   -16,    -8,     3,    19,    39,    61,    85,   107,   125,   135,
+          135,   122,    92,    44,   -21,  -105,  -205,  -316,  -432,  -546,  -648,  -729,
+         -780,  -791,  -752,  -658,  -505,  -291,   -18,   308,   679,  1082,  1502,  1924,
+         2330,  2701,  3021,  3275,  3452,  3542,  3542,  3452,  3275,  3021,  2701,  2330,
+         1924,  1502,  1082,   679,   308,   -18,  -291,  -505,  -658,  -752,  -791,  -780,
+         -729,  -648,  -546,  -432,  -316,  -205,  -105,   -21,    44,    92,   122,   135,
+          135,   125,   107,    85,    61,    39,    19,     3,    -8,   -16,   -20,   -21,
+          -20,   -18,   -15,   -12,    -9,    -7,    -6,    -5,    -5,    -5,    -6,    -6,
+           -7,    -7,    -7,    -6,    -5,    -4,    -3,    -2,    -1,     0,     1,     2
+    }},
+    // 5dB
+    {{
+            2,     1,     0,    -1,    -2,    -4,    -5,    -6,    -7,    -8,    -8,    -8,
+           -8,    -8,    -7,    -7,    -7,    -8,    -9,   -11,   -14,   -18,   -21,   -24,
+          -25,   -23,   -19,    -9,     3,    21,    44,    69,    95,   119,   139,   151,
+          150,   134,    99,    44,   -31,  -128,  -243,  -371,  -505,  -636,  -756,  -852,
+         -914,  -931,  -894,  -795,  -629,  -394,   -94,   265,   676,  1122,  1589,  2058,
+         2508,  2921,  3277,  3560,  3757,  3858,  3858,  3757,  3560,  3277,  2921,  2508,
+         2058,  1589,  1122,   676,   265,   -94,  -394,  -629,  -795,  -894,  -931,  -914,
+         -852,  -756,  -636,  -505,  -371,  -243,  -128,   -31,    44,    99,   134,   150,
+          151,   139,   119,    95,    69,    44,    21,     3,    -9,   -19,   -23,   -25,
+          -24,   -21,   -18,   -14,   -11,    -9,    -8,    -7,    -7,    -7,    -8,    -8,
+           -8,    -8,    -8,    -7,    -6,    -5,    -4,    -2,    -1,     0,     1,     2
+    }},
+    // 6dB
+    {{
+            2,     1,     0,    -1,    -3,    -4,    -6,    -7,    -9,   -10,   -10,   -10,
+          -10,    -9,    -9,    -9,    -9,   -10,   -12,   -14,   -18,   -21,   -25,   -28,
+          -29,   -27,   -22,   -11,     3,    24,    49,    77,   107,   134,   156,   168,
+          167,   148,   107,    44,   -43,  -154,  -286,  -432,  -586,  -738,  -876,  -989,
+        -1064, -1089, -1053,  -947,  -767,  -510,  -180,   218,   672,  1168,  1687,  2208,
+         2709,  3169,  3565,  3881,  4100,  4212,  4212,  4100,  3881,  3565,  3169,  2709,
+         2208,  1687,  1168,   672,   218,  -180,  -510,  -767,  -947, -1053, -1089, -1064,
+         -989,  -876,  -738,  -586,  -432,  -286,  -154,   -43,    44,   107,   148,   167,
+          168,   156,   134,   107,    77,    49,    24,     3,   -11,   -22,   -27,   -29,
+          -28,   -25,   -21,   -18,   -14,   -12,   -10,    -9,    -9,    -9,    -9,   -10,
+          -10,   -10,   -10,    -9,    -7,    -6,    -4,    -3,    -1,     0,     1,     2
+    }},
+    // 7dB
+    {{
+            3,     1,     0,    -1,    -3,    -5,    -7,    -9,   -10,   -11,   -12,   -12,
+          -12,   -11,   -11,   -11,   -11,   -12,   -14,   -17,   -21,   -26,   -30,   -33,
+          -34,   -32,   -25,   -13,     3,    27,    55,    87,   120,   150,   174,   188,
+          185,   163,   116,    43,   -56,  -183,  -334,  -501,  -678,  -852, -1012, -1143,
+        -1232, -1266, -1231, -1119,  -923,  -641,  -276,   164,   668,  1219,  1796,  2376,
+         2934,  3446,  3888,  4240,  4484,  4609,  4609,  4484,  4240,  3888,  3446,  2934,
+         2376,  1796,  1219,   668,   164,  -276,  -641,  -923, -1119, -1231, -1266, -1232,
+        -1143, -1012,  -852,  -678,  -501,  -334,  -183,   -56,    43,   116,   163,   185,
+          188,   174,   150,   120,    87,    55,    27,     3,   -13,   -25,   -32,   -34,
+          -33,   -30,   -26,   -21,   -17,   -14,   -12,   -11,   -11,   -11,   -11,   -12,
+          -12,   -12,   -11,   -10,    -9,    -7,    -5,    -3,    -1,     0,     1,     3
+    }},
+    // 8dB
+    {{
+            3,     1,     0,    -2,    -4,    -6,    -8,   -10,   -12,   -13,   -14,   -14,
+          -14,   -14,   -13,   -13,   -14,   -15,   -17,   -21,   -25,   -30,   -35,   -38,
+          -39,   -36,   -29,   -16,     3,    30,    62,    97,   134,   168,   195,   209,
+          206,   180,   127,    43,   -71,  -216,  -388,  -579,  -780,  -980, -1164, -1316,
+        -1421, -1464, -1431, -1311, -1097,  -787,  -383,   104,   664,  1277,  1919,  2565,
+         3187,  3758,  4251,  4643,  4916,  5055,  5055,  4916,  4643,  4251,  3758,  3187,
+         2565,  1919,  1277,   664,   104,  -383,  -787, -1097, -1311, -1431, -1464, -1421,
+        -1316, -1164,  -980,  -780,  -579,  -388,  -216,   -71,    43,   127,   180,   206,
+          209,   195,   168,   134,    97,    62,    30,     3,   -16,   -29,   -36,   -39,
+          -38,   -35,   -30,   -25,   -21,   -17,   -15,   -14,   -13,   -13,   -14,   -14,
+          -14,   -14,   -13,   -12,   -10,    -8,    -6,    -4,    -2,     0,     1,     3
+    }},
+    // 9dB
+    {{
+            3,     2,     0,    -2,    -4,    -7,    -9,   -12,   -14,   -15,   -16,   -17,
+          -17,   -16,   -16,   -16,   -17,   -18,   -21,   -25,   -30,   -35,   -40,   -44,
+          -45,   -42,   -33,   -18,     3,    33,    69,   109,   151,   189,   218,   234,
+          230,   199,   138,    42,   -88,  -253,  -448,  -666,  -895, -1123, -1334, -1510,
+        -1633, -1687, -1656, -1527, -1293,  -951,  -504,    37,   659,  1341,  2056,  2777,
+         3470,  4107,  4658,  5095,  5400,  5556,  5556,  5400,  5095,  4658,  4107,  3470,
+         2777,  2056,  1341,   659,    37,  -504,  -951, -1293, -1527, -1656, -1687, -1633,
+        -1510, -1334, -1123,  -895,  -666,  -448,  -253,   -88,    42,   138,   199,   230,
+          234,   218,   189,   151,   109,    69,    33,     3,   -18,   -33,   -42,   -45,
+          -44,   -40,   -35,   -30,   -25,   -21,   -18,   -17,   -16,   -16,   -16,   -17,
+          -17,   -16,   -15,   -14,   -12,    -9,    -7,    -4,    -2,     0,     2,     3
+    }}
+}};
+
+}} // mobilinkd::tnc
+
diff --git a/TNC/Fsk9600Demodulator.hpp b/TNC/Fsk9600Demodulator.hpp
new file mode 100644
index 0000000..c2b1dc7
--- /dev/null
+++ b/TNC/Fsk9600Demodulator.hpp
@@ -0,0 +1,107 @@
+// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
+// All rights reserved.
+
+#pragma once
+
+#include "Demodulator.hpp"
+#include "AudioLevel.hpp"
+#include "AudioInput.hpp"
+#include "DigitalPLL.hpp"
+#include "NRZI.hpp"
+#include "HdlcDecoder.hpp"
+#include "KissHardware.hpp"
+
+namespace mobilinkd { namespace tnc {
+
+struct Descrambler
+{
+    uint32_t state{0};
+
+    bool operator()(bool bit)
+    {
+        bool result = (bit ^ (state >> 16) ^ (state >> 11)) & 1;
+        state = ((state << 1) | (bit & 1)) & 0x1FFFF;
+        return result;
+    }
+};
+
+struct Fsk9600Demodulator : IDemodulator
+{
+    static constexpr size_t FILTER_TAP_NUM = 132;
+    static constexpr uint32_t ADC_BLOCK_SIZE = 384;
+    static constexpr uint32_t SAMPLE_RATE = 192000;
+    static_assert(audio::ADC_BUFFER_SIZE >= ADC_BLOCK_SIZE);
+
+    using bpf_coeffs_type = std::array<int16_t, FILTER_TAP_NUM>;
+    using bpf_bank_type = std::array<bpf_coeffs_type, 13>;
+    using audio_filter_t = Q15FirFilter<ADC_BLOCK_SIZE, FILTER_TAP_NUM>;
+
+    static const bpf_bank_type bpf_bank;
+
+    audio_filter_t demod_filter;
+    BaseDigitalPLL<float> pll_{192000,9600};
+    bool locked_{false};
+    Descrambler lfsr_;
+    libafsk::NRZI nrzi_;
+    hdlc::NewDecoder hdlc_decoder_;
+
+    virtual ~Fsk9600Demodulator() {}
+
+    void start() override
+    {
+        INFO("Setting 80MHz SysClock.");
+        SysClock80();
+
+        auto const& bpf_coeffs = bpf_bank[kiss::settings().rx_twist + 3];
+        const q15_t* bpf = bpf_coeffs.data();
+        demod_filter.init(bpf);
+
+        hadc1.Init.OversamplingMode = DISABLE;
+        if (HAL_ADC_Init(&hadc1) != HAL_OK)
+        {
+            CxxErrorHandler();
+        }
+//
+//        if (HAL_ADCEx_Calibration_Start(&hadc1, ADC_SINGLE_ENDED) != HAL_OK)
+//        {
+//            CxxErrorHandler();
+//        }
+
+        ADC_ChannelConfTypeDef sConfig;
+
+        sConfig.Channel = AUDIO_IN;
+        sConfig.Rank = ADC_REGULAR_RANK_1;
+        sConfig.SingleDiff = ADC_SINGLE_ENDED;
+        sConfig.SamplingTime = ADC_SAMPLETIME_92CYCLES_5;
+        sConfig.OffsetNumber = ADC_OFFSET_NONE;
+        sConfig.Offset = 0;
+        if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
+            CxxErrorHandler();
+
+        startADC(416, ADC_BLOCK_SIZE);
+    }
+
+    void stop() override
+    {
+        stopADC();
+//        INFO("Setting 4MHz SysClock.");
+//        SysClock48();
+        locked_ = false;
+    }
+
+    float readTwist() override;
+
+    hdlc::IoFrame* operator()(const q15_t* samples) override;
+
+    bool locked() const override
+    {
+        return locked_;
+    }
+
+    size_t size() const override
+    {
+        return ADC_BLOCK_SIZE;
+    }
+};
+
+}} // mobilinkd::tnc
diff --git a/TNC/Fsk9600Modulator.cpp b/TNC/Fsk9600Modulator.cpp
new file mode 100644
index 0000000..c461db6
--- /dev/null
+++ b/TNC/Fsk9600Modulator.cpp
@@ -0,0 +1,16 @@
+// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
+// All rights reserved.
+
+#include "Fsk9600Modulator.hpp"
+
+namespace mobilinkd { namespace tnc {
+
+#if 0
+const std::array<int16_t, BIT_LEN> Fsk9600Modulator::cos_table = {
+    2047,  2020,  1937,  1801,  1616,  1387,  1120,   822,   502,   169,
+    -169,  -502,  -822, -1120, -1387, -1616, -1801, -1937, -2020, -2048
+};
+
+#endif
+
+}} // mobilinkd::tnc
diff --git a/TNC/Fsk9600Modulator.hpp b/TNC/Fsk9600Modulator.hpp
new file mode 100644
index 0000000..f9e491a
--- /dev/null
+++ b/TNC/Fsk9600Modulator.hpp
@@ -0,0 +1,216 @@
+// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
+// All rights reserved.
+
+#pragma once
+
+#include "Modulator.hpp"
+
+#include <array>
+#include <algorithm>
+#include <cstdint>
+
+namespace mobilinkd { namespace tnc {
+
+struct Scrambler
+{
+    uint32_t state{0};
+
+    bool operator()(bool bit)
+    {
+        bool result = (bit ^ (state >> 16) ^ (state >> 11)) & 1;
+        state = ((state << 1) | result) & 0x1FFFF;
+        return result;
+    }
+};
+
+struct Fsk9600Modulator : Modulator
+{
+    static constexpr int8_t DAC_BUFFER_LEN = 40;
+    static constexpr int8_t BIT_LEN = DAC_BUFFER_LEN / 2;
+
+    static constexpr std::array<int16_t, BIT_LEN> cos_table{
+        2047,  2020,  1937,  1801,  1616,  1387,  1120,   822,   502,   169,
+        -169,  -502,  -822, -1120, -1387, -1616, -1801, -1937, -2020, -2048
+    };
+
+    enum class Level { ZERO, HIGH, LOW };
+    enum class State { STOPPED, STARTING, RUNNING, STOPPING };
+
+    osMessageQId dacOutputQueueHandle_{0};
+    PTT* ptt_{nullptr};
+    uint16_t volume_{4096};
+    std::array<uint16_t, DAC_BUFFER_LEN> buffer_;
+    Level level{Level::HIGH};
+    State state{State::STOPPED};
+    Scrambler lfsr;
+
+    Fsk9600Modulator(osMessageQId queue, PTT* ptt)
+    : dacOutputQueueHandle_(queue), ptt_(ptt)
+    {}
+
+    ~Fsk9600Modulator() override {}
+
+    void init(const kiss::Hardware& hw) override
+    {
+        for (auto& x : buffer_) x = 2048;
+
+        state = State::STOPPED;
+        level = Level::HIGH;
+
+        // Configure 80MHz clock for 192ksps.
+        htim7.Init.Period = 416;
+        if (HAL_TIM_Base_Init(&htim7) != HAL_OK)
+        {
+            ERROR("htim7 init failed");
+            CxxErrorHandler();
+        }
+    }
+
+    void deinit() override
+    {
+        state = State::STOPPED;
+        HAL_DAC_Stop_DMA(&hdac1, DAC_CHANNEL_1);
+        HAL_TIM_Base_Stop(&htim7);
+        ptt_->off();
+    }
+
+    void set_gain(uint16_t level) override
+    {
+        auto v = std::max<uint16_t>(256, level);
+        v = std::min<uint16_t>(4096, v);
+        volume_ = v;
+    }
+
+    void set_ptt(PTT* ptt) override
+    {
+        if (state != State::STOPPED)
+        {
+            ERROR("PTT change while not stopped");
+            CxxErrorHandler();
+        }
+        ptt_ = ptt;
+        ptt_->off();
+    }
+
+    void send(bool bit) override
+    {
+        auto scrambled = lfsr(bit);
+
+        switch (state)
+        {
+        case State::STOPPING:
+        case State::STOPPED:
+            fill_first(scrambled);
+            state = State::STARTING;
+            break;
+        case State::STARTING:
+            fill_last(scrambled);
+            state = State::RUNNING;
+            ptt_->on();
+            HAL_TIM_Base_Start(&htim7);
+            HAL_DAC_Start_DMA(
+                &hdac1, DAC_CHANNEL_1,
+                reinterpret_cast<uint32_t*>(buffer_.data()), buffer_.size(),
+                DAC_ALIGN_12B_R);
+            break;
+        case State::RUNNING:
+            osMessagePut(dacOutputQueueHandle_, scrambled, osWaitForever);
+            break;
+        }
+    }
+
+    // DAC DMA interrupt functions.
+
+    void fill_first(bool bit) override
+    {
+        fill(buffer_.data(), bit);
+    }
+
+    void fill_last(bool bit) override
+    {
+        fill(buffer_.data() + BIT_LEN, bit);
+    }
+
+    void empty() override
+    {
+        switch (state)
+        {
+        case State::STARTING:
+            // fall-through
+        case State::RUNNING:
+            state = State::STOPPING;
+            break;
+        case State::STOPPING:
+            state = State::STOPPED;
+            HAL_DAC_Stop_DMA(&hdac1, DAC_CHANNEL_1);
+            HAL_TIM_Base_Stop(&htim7);
+            ptt_->off();
+            break;
+        case State::STOPPED:
+            break;
+        }
+        state = State::STOPPING;
+        level = Level::HIGH;
+    }
+
+    void abort() override
+    {
+        state = State::STOPPED;
+        HAL_DAC_Stop_DMA(&hdac1, DAC_CHANNEL_1);
+        HAL_TIM_Base_Stop(&htim7);
+        ptt_->off();
+
+        // Drain the queue.
+        while (osMessageGet(dacOutputQueueHandle_, 0).status == osEventMessage);
+    }
+
+    float bits_per_ms() const override
+    {
+        return 9.6f;
+    }
+
+private:
+
+    uint16_t adjust_level(int32_t sample) const
+    {
+        sample *= volume_;
+        sample >>= 12;
+        sample += 2048;
+        return sample;
+    }
+
+    void fill(uint16_t* buffer, bool bit)
+    {
+        switch (level)
+        {
+        case Level::HIGH:
+            if (bit)
+            {
+                std::fill(buffer, buffer + BIT_LEN, adjust_level(2047));
+            }
+            else
+            {
+                std::transform(cos_table.begin(), cos_table.end(), buffer,
+                    [this](auto x){return adjust_level(x);});
+                level = Level::LOW;
+            }
+            break;
+        case Level::LOW:
+            if (bit)
+            {
+                std::transform(cos_table.rbegin(), cos_table.rend(), buffer,
+                    [this](auto x){return adjust_level(x);});
+                level = Level::HIGH;
+            }
+            else
+            {
+                std::fill(buffer, buffer + BIT_LEN, adjust_level(-2048));
+            }
+            break;
+        default:
+            CxxErrorHandler();
+        }
+    }
+};
+
+}} // mobilinkd::tnc
diff --git a/TNC/Goertzel.h b/TNC/Goertzel.h
index 47e8b90..3ccefac 100644
--- a/TNC/Goertzel.h
+++ b/TNC/Goertzel.h
@@ -1,94 +1,102 @@
 // Copyright 2017 Rob Riggs <rob@mobilinkd.com>
 // All rights reserved.
 
-#ifndef MOBILINKD__TNC__GOERTZEL_FILTER_HPP_
-#define MOBILINKD__TNC__GOERTZEL_FILTER_HPP_
+#pragma once
 
 #include "AudioLevel.hpp"
 #include <arm_math.h>
 #include <complex>
 
-namespace mobilinkd { namespace tnc {
+namespace mobilinkd {
+namespace tnc {
 
 extern const float WINDOW[];
 
-template <uint32_t SAMPLES, uint32_t SAMPLE_RATE>
+template<uint32_t SAMPLES, uint32_t SAMPLE_RATE>
 class GoertzelFilter
 {
-	float filterFreq_;
-	int bin_;
-	float coeff_;
-  float d1{0.0f};
-  float d2{0.0f};
-  uint32_t count{0};
-  const float* window_;
-	
+    float filterFreq_;
+    int bin_;
+    float coeff_;
+    float d1 { 0.0f };
+    float d2 { 0.0f };
+    uint32_t count { 0 };
+    const float* window_;
+
 public:
-	GoertzelFilter(float filter_freq, const float* window = WINDOW)
-	: filterFreq_(filter_freq)
-	, bin_(0.5f + ((filter_freq * SAMPLES) / SAMPLE_RATE))
-	, coeff_(2.0f * cos((2.0f * M_PI * bin_) / float(SAMPLES)))
-  , window_(window)
-	{}
-	
-	void operator()(float* samples, uint32_t n) {
-
-	  for (size_t i = 0; i != n; ++i) {
-	      float w = window_ ? window_[count] : 1.0;
-	      float y  = w * samples[i] + coeff_ * d1 - d2;
-	      d2 = d1;
-	      d1 = y;
-	      ++count;
-	  }
-	}
-	
-  void operator()(uint16_t* samples, uint32_t n) {
-
-    for (uint32_t i = 0; i != n; ++i) {
-        float w = window_ ? window_[count] : 1.0;
-        float sample = (float(samples[i]) - audio::virtual_ground) * audio::i_vgnd;
-        float y = w * sample + coeff_ * d1 - d2;
-        d2 = d1;
-        d1 = y;
-        ++count;
+    GoertzelFilter(float filter_freq, const float* window = WINDOW)
+        : filterFreq_(filter_freq), bin_(
+            0.5f + ((filter_freq * SAMPLES) / SAMPLE_RATE)), coeff_(
+            2.0f * cos((2.0f * M_PI * bin_) / float(SAMPLES))), window_(window)
+    {
     }
-  }
 
-  operator float() const {
-    return d2 * d2 + d1 * d1 - coeff_ * d1 * d2;
-  }
+    void operator()(float* samples, uint32_t n)
+    {
 
-  void reset() {
-    d1 = 0.0f;
-    d2 = 0.0f;
-    count = 0;
-  }
+        for (size_t i = 0; i != n; ++i)
+        {
+            float w = window_ ? window_[count] : 1.0;
+            float y = w * samples[i] + coeff_ * d1 - d2;
+            d2 = d1;
+            d1 = y;
+            ++count;
+        }
+    }
+
+    void operator()(uint16_t* samples, uint32_t n)
+    {
+
+        for (uint32_t i = 0; i != n; ++i)
+        {
+            float w = window_ ? window_[count] : 1.0;
+            float sample = (float(samples[i]) - audio::virtual_ground)
+                * audio::i_vgnd;
+            float y = w * sample + coeff_ * d1 - d2;
+            d2 = d1;
+            d1 = y;
+            ++count;
+        }
+    }
+
+    operator float() const
+    {
+        return d2 * d2 + d1 * d1 - coeff_ * d1 * d2;
+    }
+
+    void reset()
+    {
+        d1 = 0.0f;
+        d2 = 0.0f;
+        count = 0;
+    }
 };
 
 #if 0
 template <uint32_t SAMPLES, uint32_t SAMPLE_RATE>
 class GoertzelFactory
 {
-  float window_[SAMPLES];
-  static void make_window(float* window)
-  {
-    for (size_t i = 0; i != SAMPLES; ++i) {
-      window[i] = 0.54f - 0.46f * cos(2.0f * M_PI * (float(i) / float(SAMPLE_RATE)));
+    float window_[SAMPLES];
+    static void make_window(float* window)
+    {
+        for (size_t i = 0; i != SAMPLES; ++i)
+        {
+            window[i] = 0.54f - 0.46f * cos(2.0f * M_PI * (float(i) / float(SAMPLE_RATE)));
+        }
     }
-  }
 
 public:
 
-  GoertzelFactory()
-  : window_()
-  {
-    make_window(window_);
-  }
+    GoertzelFactory()
+    : window_()
+    {
+        make_window(window_);
+    }
 
-  GoertzelFilter<SAMPLES, SAMPLE_RATE> make(float freq)
-  {
-    return GoertzelFilter<SAMPLES, SAMPLE_RATE>(freq, window_);
-  }
+    GoertzelFilter<SAMPLES, SAMPLE_RATE> make(float freq)
+    {
+        return GoertzelFilter<SAMPLES, SAMPLE_RATE>(freq, window_);
+    }
 };
 #endif
 
@@ -104,20 +112,22 @@ struct Goertzel
     float_type sin_;
     float_type cos_;
     float_type coeff_;
-    float_type q0{0.0}, q1{0.0}, q2{0.0};
+    float_type q0 { 0.0 }, q1 { 0.0 }, q2 { 0.0 };
     explicit Goertzel(float_type omega)
-    : sin_(sin(omega)), cos_(cos(omega)), coeff_(2.0 * cos_)
-    {}
+        : sin_(sin(omega)), cos_(cos(omega)), coeff_(2.0 * cos_)
+    {
+    }
 
     static type from_frequency(float_type frequency, float_type sample_rate)
     {
         return Goertzel(2.0 * PI * frequency / sample_rate);
     }
 
-    template <typename Container>
+    template<typename Container>
     complex_type operator()(const Container& data)
     {
-        for (auto& v : data) {
+        for (auto& v : data)
+        {
             q0 = coeff_ * q1 - q2 + v;
             q2 = q1;
             q1 = q0;
@@ -134,6 +144,6 @@ struct Goertzel
 
 typedef Goertzel<float> FloatGoertzel;
 
-}} // mobilinkd::tnc
+}
+} // mobilinkd::tnc
 
-#endif // MOBILINKD__TNC__GOERTZEL_FILTER_HPP_
diff --git a/TNC/HDLCEncoder.hpp b/TNC/HDLCEncoder.hpp
index ea8ccf8..6cf190e 100644
--- a/TNC/HDLCEncoder.hpp
+++ b/TNC/HDLCEncoder.hpp
@@ -4,7 +4,7 @@
 #ifndef INC_HDLCENCODER_HPP_
 #define INC_HDLCENCODER_HPP_
 
-#include "AFSKModulator.hpp"
+#include "Modulator.hpp"
 #include "HdlcFrame.hpp"
 #include "NRZI.hpp"
 #include "PTT.hpp"
@@ -47,11 +47,11 @@ struct Encoder {
     NRZI nrzi_;
     uint16_t crc_;
     osMessageQId input_;
-    AFSKModulator* modulator_;
+    Modulator* modulator_;
     volatile bool running_;
     bool send_delay_;   // Avoid sending the preamble for back-to-back frames.
 
-    Encoder(osMessageQId input, AFSKModulator* output)
+    Encoder(osMessageQId input, Modulator* output)
     : tx_delay_(kiss::settings().txdelay), tx_tail_(kiss::settings().txtail)
     , p_persist_(kiss::settings().ppersist), slot_time_(kiss::settings().slot)
     , duplex_(kiss::settings().duplex), state_(state_type::STATE_IDLE)
@@ -192,7 +192,7 @@ struct Encoder {
     }
 
     void send_delay() {
-        const size_t tmp = (tx_delay_ * 3) / 2;
+        const size_t tmp = tx_delay_ * modulator_->bits_per_ms();
         for (size_t i = 0; i != tmp; i++) {
             send_raw(IDLE);
         }
diff --git a/TNC/IOEventTask.cpp b/TNC/IOEventTask.cpp
index 148fafc..ad2792e 100644
--- a/TNC/IOEventTask.cpp
+++ b/TNC/IOEventTask.cpp
@@ -60,6 +60,7 @@ void startIOEventTask(void const*)
         hardware.init();
         hardware.store();
     }
+//    hardware.init();
 
     osMutexRelease(hardwareInitMutexHandle);
 
@@ -106,6 +107,7 @@ void startIOEventTask(void const*)
             DEBUG("USB connected -- negotiate");
             HAL_GPIO_WritePin(BT_SLEEP_GPIO_Port, BT_SLEEP_Pin,
                 GPIO_PIN_RESET);
+//            SysClock48();
             osTimerStart(usbShutdownTimerHandle, 5000);
         }
     }
@@ -151,6 +153,7 @@ void startIOEventTask(void const*)
                     hpcd_USB_FS.Instance->BCDR = 0;
                     HAL_PCD_MspDeInit(&hpcd_USB_FS);
                     HAL_GPIO_WritePin(USB_CE_GPIO_Port, USB_CE_Pin, GPIO_PIN_SET);
+//                    SysClock4();
                     if (ioport != getUsbPort())
                     {
                         break;
@@ -272,6 +275,7 @@ void startIOEventTask(void const*)
                 break;
             case CMD_USB_CONNECTED:
                 INFO("VBUS Detected");
+//                SysClock48();
                 MX_USB_DEVICE_Init();
                 HAL_PCD_MspInit(&hpcd_USB_FS);
                 hpcd_USB_FS.Instance->BCDR = 0;
diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index 8297997..13e29e8 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -9,6 +9,7 @@
 #include <ModulatorTask.hpp>
 
 #include <memory>
+#include <array>
 #include <cstdio>
 
 extern I2C_HandleTypeDef hi2c1;
@@ -26,9 +27,17 @@ int powerOffViaUSB(void)
 
 namespace mobilinkd { namespace tnc { namespace kiss {
 
-const char FIRMWARE_VERSION[] = "1.1.6";
+const char FIRMWARE_VERSION[] = "2.0.0a1";
 const char HARDWARE_VERSION[] = "Mobilinkd TNC3 2.1.1";
 
+
+const std::array<const char*, 4> modem_type_lookup = {
+    "NOT SET",
+    "AFSK1200",
+    "AFSK300",
+    "FSK9600",
+};
+
 Hardware& settings()
 {
     static Hardware instance __attribute__((section(".bss3")));
@@ -119,7 +128,7 @@ inline void reply(uint8_t cmd, const uint8_t* data, uint16_t len) {
 }
 
 inline void reply_ext(uint8_t ext, uint8_t cmd, const uint8_t* data, uint16_t len) {
-    auto buffer = (uint8_t*) malloc(len + 2);
+    auto buffer = static_cast<uint8_t*>(alloca(len + 2));
     if (buffer == nullptr) return;
     buffer[0] = ext;
     buffer[1] = cmd;
@@ -337,7 +346,7 @@ void Hardware::handle_request(hdlc::IoFrame* frame) {
         if (tx_twist < 0) tx_twist = 0;
         if (tx_twist > 100) tx_twist = 100;
         DEBUG("SET_OUTPUT_TWIST: %d", int(tx_twist));
-        getModulator().set_twist(uint8_t(tx_twist));
+        getModulator().init(*this);
         update_crc();
         [[fallthrough]];
     case hardware::GET_OUTPUT_TWIST:
@@ -376,6 +385,26 @@ void Hardware::handle_request(hdlc::IoFrame* frame) {
         reply8(hardware::GET_DUPLEX, duplex);
         break;
 
+    case hardware::SET_MODEM_TYPE:
+        DEBUG("SET_MODEM_TYPE");
+        if ((*it > 0) and (*it < 4))
+        {
+            modem_type = *it;
+            DEBUG(modem_type_lookup[*it]);
+            update_crc();
+        }
+        else
+        {
+            ERROR("Unknown modem type");
+        }
+        osMessagePut(audioInputQueueHandle, audio::UPDATE_SETTINGS,
+            osWaitForever);
+        [[fallthrough]];
+    case hardware::GET_MODEM_TYPE:
+        DEBUG("GET_MODEM_TYPE");
+        reply8(hardware::GET_MODEM_TYPE, modem_type);
+        break;
+
     case hardware::GET_FIRMWARE_VERSION:
         DEBUG("GET_FIRMWARE_VERSION");
         reply(hardware::GET_FIRMWARE_VERSION, (uint8_t*) FIRMWARE_VERSION,
diff --git a/TNC/KissHardware.hpp b/TNC/KissHardware.hpp
index 527aff9..7881a15 100644
--- a/TNC/KissHardware.hpp
+++ b/TNC/KissHardware.hpp
@@ -94,6 +94,9 @@ constexpr const uint8_t GET_TIMESLOT = 35;
 constexpr const uint8_t GET_TXTAIL = 36;
 constexpr const uint8_t GET_DUPLEX = 37;
 
+constexpr const uint8_t SET_MODEM_TYPE = 38;
+constexpr const uint8_t GET_MODEM_TYPE = 39;
+
 constexpr const uint8_t GET_FIRMWARE_VERSION = 40;
 constexpr const uint8_t GET_HARDWARE_VERSION = 41;
 constexpr const uint8_t SAVE_EEPROM_SETTINGS = 42;
@@ -269,7 +272,7 @@ struct Hardware
       slot = 10;
       txtail = 1;
       duplex = 0;
-      modem_type = ModemType::AFSK1200;
+      modem_type = ModemType::FSK9600;
       output_gain = 63;
       input_gain = 0;   // 0-4 on TNC3
       tx_twist = 50;
diff --git a/TNC/Modulator.hpp b/TNC/Modulator.hpp
new file mode 100644
index 0000000..9d3982c
--- /dev/null
+++ b/TNC/Modulator.hpp
@@ -0,0 +1,93 @@
+// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
+// All rights reserved.
+
+#pragma once
+
+#include "PTT.hpp"
+#include "KissHardware.hpp"
+
+#include "cmsis_os.h"
+
+#include <cstdint>
+
+extern osMessageQId hdlcOutputQueueHandle;
+extern osMessageQId dacOutputQueueHandle;
+extern TIM_HandleTypeDef htim7;
+extern DAC_HandleTypeDef hdac1;
+
+namespace mobilinkd { namespace tnc {
+
+/**
+ * The modulator has three distinct interfaces.  The configuration interface
+ * which is used to initialize the modulator, the bit sending interface used
+ * by the HDLC encoder to transmit the bits, and the modulation interface
+ * used by the DAC DMA engine to get the analog values output by the modem.
+ */
+struct Modulator
+{
+    virtual ~Modulator() {}
+
+    /**
+     * Implement all functionality required to configure the hardware and
+     * the modulator.  For example, configuring the timer used by the DAC
+     * should be done here.
+     */
+    virtual void init(const kiss::Hardware& hw) = 0;
+
+    /**
+     * Implement all functionality required to deactivate the hardware and
+     * the modulator.  For example, disabling the timer used by the DAC
+     * should be done here.
+     */
+    virtual void deinit() = 0;
+
+    virtual void set_gain(uint16_t level) = 0;
+
+    /**
+     * Set the PTT controller used by the modulator.  It is only legal
+     * to call this when the modulator is stopped.
+     *
+     * @param ptt
+     */
+    virtual void set_ptt(PTT* ptt) = 0;
+
+    /**
+     * Send a single bit.
+     *
+     * @param bit
+     */
+    virtual void send(bool bit) = 0;
+
+    /// The next three functions are called by the DAC DMA interrupt handler.
+
+    /**
+     * Fill the first half of the DAC DMA buffer.
+     *
+     * @warning This function is called in an interrupt context.
+     *
+     * @param bit
+     */
+    virtual void fill_first(bool bit) = 0;
+
+    /**
+     * Fill the second half of the DAC DMA buffer.
+     *
+     * @warning This function is called in an interrupt context.
+     *
+     * @param bit
+     */
+    virtual void fill_last(bool bit) = 0;
+
+    /**
+     * The DAC bit buffer is empty.  There are no more bits to process.
+     *
+     * @warning This function is called in an interrupt context.
+     */
+    virtual void empty() = 0;
+
+    virtual void abort() = 0;
+
+    virtual float bits_per_ms() const = 0;
+};
+
+}} // mobilinkd::tnc
diff --git a/TNC/ModulatorTask.cpp b/TNC/ModulatorTask.cpp
index 286a52f..73d7136 100644
--- a/TNC/ModulatorTask.cpp
+++ b/TNC/ModulatorTask.cpp
@@ -2,13 +2,15 @@
 // All rights reserved.
 
 #include "ModulatorTask.hpp"
+#include "Fsk9600Modulator.hpp"
+#include "AFSKModulator.hpp"
 #include "KissHardware.hpp"
 #include "main.h"
 
 mobilinkd::tnc::SimplexPTT simplexPtt;
 mobilinkd::tnc::MultiplexPTT multiplexPtt;
 
-mobilinkd::tnc::AFSKModulator* modulator;
+mobilinkd::tnc::Modulator* modulator;
 mobilinkd::tnc::hdlc::Encoder* encoder;
 
 // DMA Conversion half complete.
@@ -34,9 +36,22 @@ extern "C" void HAL_DAC_DMAUnderrunCallbackCh1(DAC_HandleTypeDef*) {
     modulator->abort();
 }
 
-mobilinkd::tnc::AFSKModulator& getModulator() {
-    static mobilinkd::tnc::AFSKModulator instance(dacOutputQueueHandle, &simplexPtt);
-    return instance;
+mobilinkd::tnc::Modulator& getModulator()
+{
+    using namespace mobilinkd::tnc;
+
+    static AFSKModulator afsk1200modulator(dacOutputQueueHandle, &simplexPtt);
+    static Fsk9600Modulator fsk9600modulator(dacOutputQueueHandle, &simplexPtt);
+
+    switch (kiss::settings().modem_type)
+    {
+    case kiss::Hardware::ModemType::FSK9600:
+        return fsk9600modulator;
+    case kiss::Hardware::ModemType::AFSK1200:
+        return afsk1200modulator;
+    default:
+        _Error_Handler(__FILE__, __LINE__);
+    }
 }
 
 mobilinkd::tnc::hdlc::Encoder& getEncoder() {
@@ -61,9 +76,9 @@ void updatePtt()
     using namespace mobilinkd::tnc::kiss;
 
     if (settings().options & KISS_OPTION_PTT_SIMPLEX)
-        modulator->set_ptt(&simplexPtt);
+        getModulator().set_ptt(&simplexPtt);
     else
-        modulator->set_ptt(&multiplexPtt);
+        getModulator().set_ptt(&multiplexPtt);
 }
 
 void startModulatorTask(void const*) {
@@ -78,7 +93,7 @@ void startModulatorTask(void const*) {
 
     updatePtt();
 
-    modulator->set_twist(settings().tx_twist);
+    getModulator().init(settings());
 
     encoder->tx_delay(settings().txdelay);
     encoder->p_persist(settings().ppersist);
diff --git a/TNC/ModulatorTask.hpp b/TNC/ModulatorTask.hpp
index 9f9ccfe..b52c98c 100644
--- a/TNC/ModulatorTask.hpp
+++ b/TNC/ModulatorTask.hpp
@@ -6,7 +6,7 @@
 #define MOBILINKD__MODULATOR_TASK_HPP_
 
 #include "HDLCEncoder.hpp"
-#include "AFSKModulator.hpp"
+#include "Modulator.hpp"
 #include "PTT.hpp"
 #include "cmsis_os.h"
 
@@ -17,11 +17,7 @@ extern "C" {
 extern mobilinkd::tnc::SimplexPTT simplexPtt;
 extern mobilinkd::tnc::MultiplexPTT multiplexPtt;
 
-extern mobilinkd::tnc::AFSKModulator* modulator;
-extern mobilinkd::tnc::hdlc::Encoder* encoder;
-
-mobilinkd::tnc::AFSKModulator& getModulator();
-mobilinkd::tnc::hdlc::Encoder& getEncoder();
+mobilinkd::tnc::Modulator& getModulator();
 
 void startModulatorTask(void const * argument);
 
diff --git a/stlink-tnc3.cfg b/stlink-tnc3.cfg
index 2c95e4f..37aaca1 100644
--- a/stlink-tnc3.cfg
+++ b/stlink-tnc3.cfg
@@ -9,5 +9,5 @@ source [find target/stm32l4x.cfg]
 
 reset_config srst_only
 itm port 0 on
-tpiu config internal swv uart off 48000000
+tpiu config internal swv uart off 80000000
 

From 464b05481d9687c75784d816cea7d9f0d34a7926 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sat, 22 Feb 2020 19:06:26 -0600
Subject: [PATCH 03/36] Add noreturn attribute to _Error_Handler() to squelch
 warnings.

---
 Inc/main.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Inc/main.h b/Inc/main.h
index 5cc3cf8..b39688d 100644
--- a/Inc/main.h
+++ b/Inc/main.h
@@ -187,7 +187,7 @@ void SysClock4(void);
 #ifdef __cplusplus
  extern "C" {
 #endif
-void _Error_Handler(char *, int);
+void _Error_Handler(char *, int) __attribute__ ((noreturn));
 
 #define Error_Handler() _Error_Handler(__FILE__, __LINE__)
 #ifdef __cplusplus

From 0e4ad6a24957c5a4a600acc8962409c0a41ad59d Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sat, 22 Feb 2020 19:09:23 -0600
Subject: [PATCH 04/36] Enable HSI clock and drive I2C and UART from it so
 communication is not interrupted on clock change.  Explicitly disable LSCO
 for release builds.

---
 Src/main.c | 100 ++++++++++++++++++-----------------------------------
 1 file changed, 34 insertions(+), 66 deletions(-)

diff --git a/Src/main.c b/Src/main.c
index 749f553..e0dd06f 100644
--- a/Src/main.c
+++ b/Src/main.c
@@ -457,6 +457,10 @@ int main(void)
 
   encode_serial_number();
 
+  // Manchester encoding mode on SWO.
+  // *((volatile unsigned *)(TPI->SPPR)) = 0x00000001;
+
+
   if (!go_back_to_sleep) {
       // The Bluetooth module is powered on during MX_GPIO_Init().  BT_CMD
       // has a weak pull-up on the BT module and is in OD mode.  Pull the
@@ -701,18 +705,18 @@ void SystemClock_Config(void)
     /**Initializes the CPU, AHB and APB busses clocks 
     */
   RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_LSI|RCC_OSCILLATORTYPE_LSE
-                              |RCC_OSCILLATORTYPE_MSI;
+                              |RCC_OSCILLATORTYPE_MSI|RCC_OSCILLATORTYPE_HSI;
   RCC_OscInitStruct.LSEState = RCC_LSE_ON;
   RCC_OscInitStruct.LSIState = RCC_LSI_OFF;
   RCC_OscInitStruct.MSIState = RCC_MSI_ON;
-  RCC_OscInitStruct.HSIState = RCC_HSI_OFF;
+  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
   RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
   RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
   RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
   RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
   RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
   RCC_OscInitStruct.PLL.PLLM = 1;
-  RCC_OscInitStruct.PLL.PLLN = 40;
+  RCC_OscInitStruct.PLL.PLLN = 24;
   RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV7;
   RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
   RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
@@ -738,8 +742,8 @@ void SystemClock_Config(void)
   PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_RTC|RCC_PERIPHCLK_USART3
                               |RCC_PERIPHCLK_I2C1|RCC_PERIPHCLK_USB
                               |RCC_PERIPHCLK_RNG|RCC_PERIPHCLK_ADC;
-  PeriphClkInit.Usart3ClockSelection = RCC_USART3CLKSOURCE_PCLK1;
-  PeriphClkInit.I2c1ClockSelection = RCC_I2C1CLKSOURCE_PCLK1;
+  PeriphClkInit.Usart3ClockSelection = RCC_USART3CLKSOURCE_HSI;
+  PeriphClkInit.I2c1ClockSelection = RCC_I2C1CLKSOURCE_HSI;
   PeriphClkInit.AdcClockSelection = RCC_ADCCLKSOURCE_SYSCLK;
   PeriphClkInit.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;
   PeriphClkInit.UsbClockSelection = RCC_USBCLKSOURCE_PLLSAI1;
@@ -758,6 +762,8 @@ void SystemClock_Config(void)
 
 #ifdef KISS_LOGGING
   HAL_RCCEx_EnableLSCO(RCC_LSCOSOURCE_LSE);
+#else
+  HAL_RCCEx_DisableLSCO();
 #endif
 
     /**Configure the main internal regulator output voltage
@@ -907,8 +913,9 @@ static void MX_I2C1_Init(void)
 {
 
   hi2c1.Instance = I2C1;
-//  hi2c1.Init.Timing = 0x00300F33;
-  hi2c1.Init.Timing = 0x20000209;
+//  hi2c1.Init.Timing = 0x00300F33;   // 80MHz
+//  hi2c1.Init.Timing = 0x20000209;   // 48MHz
+  hi2c1.Init.Timing = 0x00000107;   // HSI
   hi2c1.Init.OwnAddress1 = 0;
   hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
   hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
@@ -1444,29 +1451,19 @@ void SysClock48()
 
     if (HAL_RCC_GetHCLKFreq() == 48000000) return;
 
-    taskENTER_CRITICAL();
+    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
+    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
 
-    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
-                                |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
-    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
-    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
-    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
-    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
-
-    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
+    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
     {
       _Error_Handler(__FILE__, __LINE__);
     }
 
-    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_LSI|RCC_OSCILLATORTYPE_LSE
-                                |RCC_OSCILLATORTYPE_MSI;
-    RCC_OscInitStruct.LSEState = RCC_LSE_ON;
-    RCC_OscInitStruct.LSIState = RCC_LSI_OFF;
-    RCC_OscInitStruct.MSIState = RCC_MSI_ON;
-    RCC_OscInitStruct.HSIState = RCC_HSI_OFF;
-    RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
-    RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
-    RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
+    /**Configure the Systick interrupt time
+    */
+    HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
+
+    RCC_OscInitStruct.OscillatorType = 0;
     RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
     RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
     RCC_OscInitStruct.PLL.PLLM = 1;
@@ -1479,14 +1476,8 @@ void SysClock48()
       _Error_Handler(__FILE__, __LINE__);
     }
 
-      /**Initializes the CPU, AHB and APB busses clocks
-      */
-    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
-                                |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
+    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
     RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
-    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
-    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
-    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
 
     if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
     {
@@ -1496,8 +1487,6 @@ void SysClock48()
     /**Configure the Systick interrupt time
     */
     HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
-
-    taskEXIT_CRITICAL();
 }
 
 void SysClock80()
@@ -1507,29 +1496,19 @@ void SysClock80()
 
     if (HAL_RCC_GetHCLKFreq() == 80000000) return;
 
-    taskENTER_CRITICAL();
+    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
+    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
 
-    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
-                                |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
-    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
-    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
-    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
-    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
-
-    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
+    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
     {
       _Error_Handler(__FILE__, __LINE__);
     }
 
-    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_LSI|RCC_OSCILLATORTYPE_LSE
-                                |RCC_OSCILLATORTYPE_MSI|RCC_OSCILLATORTYPE_HSI;
-    RCC_OscInitStruct.LSEState = RCC_LSE_ON;
-    RCC_OscInitStruct.LSIState = RCC_LSI_OFF;
-    RCC_OscInitStruct.MSIState = RCC_MSI_ON;
-    RCC_OscInitStruct.HSIState = RCC_HSI_OFF;
-    RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
-    RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
-    RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
+    /**Configure the Systick interrupt time
+    */
+    HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
+
+    RCC_OscInitStruct.OscillatorType = 0;
     RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
     RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
     RCC_OscInitStruct.PLL.PLLM = 1;
@@ -1542,14 +1521,8 @@ void SysClock80()
       _Error_Handler(__FILE__, __LINE__);
     }
 
-      /**Initializes the CPU, AHB and APB busses clocks
-      */
-    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
-                                |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
+    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
     RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
-    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
-    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
-    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
 
     if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)
     {
@@ -1559,8 +1532,6 @@ void SysClock80()
     /**Configure the Systick interrupt time
     */
     HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
-
-    taskEXIT_CRITICAL();
 }
 
 void SysClock4()
@@ -1570,12 +1541,8 @@ void SysClock4()
 
     taskENTER_CRITICAL();
 
-    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
-                                |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
+    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
     RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
-    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
-    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
-    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
 
     if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
     {
@@ -1616,6 +1583,7 @@ void StartDefaultTask(void const * argument)
 #ifdef KISS_LOGGING
     printf("VBUS not detected\r\n");
 #endif
+//    SysClock4();
   }
 /* Infinite loop */
   for(;;)

From 897aabd41463184ffa257691a01b5f17a594c2da Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sat, 22 Feb 2020 19:11:03 -0600
Subject: [PATCH 05/36] Update STMCubeMX IOC file to nable HSI clock and drive
 I2C and UART from HSI so communication is not interrupted on clock change.

---
 firmware.ioc | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/firmware.ioc b/firmware.ioc
index a6d724a..12ee479 100644
--- a/firmware.ioc
+++ b/firmware.ioc
@@ -99,7 +99,7 @@ FREERTOS.configUSE_TIMERS=1
 File.Version=6
 I2C1.I2C_Speed_Mode=I2C_Fast_Plus
 I2C1.IPParameters=I2C_Speed_Mode,Timing
-I2C1.Timing=0x20000209
+I2C1.Timing=0x00000107
 KeepUserPlacement=true
 Mcu.Family=STM32L4
 Mcu.IP0=ADC1
@@ -475,10 +475,11 @@ RCC.HCLKFreq_Value=48000000
 RCC.HSE_VALUE=8000000
 RCC.HSI48_VALUE=48000000
 RCC.HSI_VALUE=16000000
-RCC.I2C1Freq_Value=48000000
+RCC.I2C1CLockSelection=RCC_I2C1CLKSOURCE_HSI
+RCC.I2C1Freq_Value=16000000
 RCC.I2C2Freq_Value=48000000
 RCC.I2C3Freq_Value=48000000
-RCC.IPParameters=ADCFreq_Value,AHBFreq_Value,APB1Freq_Value,APB1TimFreq_Value,APB2Freq_Value,APB2TimFreq_Value,CortexFreq_Value,FCLKCortexFreq_Value,FamilyName,HCLKFreq_Value,HSE_VALUE,HSI48_VALUE,HSI_VALUE,I2C1Freq_Value,I2C2Freq_Value,I2C3Freq_Value,LCDFreq_Value,LPTIM1Freq_Value,LPTIM2Freq_Value,LPUART1Freq_Value,LSCOPinFreq_Value,LSCOSource1,LSE_Drive_Capability,LSI_VALUE,MCO1PinFreq_Value,MSI_VALUE,PLLN,PLLPoutputFreq_Value,PLLQoutputFreq_Value,PLLRCLKFreq_Value,PLLSAI1N,PLLSAI1PoutputFreq_Value,PLLSAI1QoutputFreq_Value,PLLSAI1RoutputFreq_Value,PREFETCH_ENABLE,PWRFreq_Value,RCC_MCO1Source,RNGFreq_Value,RTCClockSelection,RTCFreq_Value,SAI1Freq_Value,SWPMI1Freq_Value,SYSCLKFreq_VALUE,SYSCLKSource,USART1Freq_Value,USART2Freq_Value,USART3Freq_Value,USBFreq_Value,VCOInputFreq_Value,VCOOutputFreq_Value,VCOSAI1OutputFreq_Value
+RCC.IPParameters=ADCFreq_Value,AHBFreq_Value,APB1Freq_Value,APB1TimFreq_Value,APB2Freq_Value,APB2TimFreq_Value,CortexFreq_Value,FCLKCortexFreq_Value,FamilyName,HCLKFreq_Value,HSE_VALUE,HSI48_VALUE,HSI_VALUE,I2C1CLockSelection,I2C1Freq_Value,I2C2Freq_Value,I2C3Freq_Value,LCDFreq_Value,LPTIM1Freq_Value,LPTIM2Freq_Value,LPUART1Freq_Value,LSCOPinFreq_Value,LSCOSource1,LSE_Drive_Capability,LSI_VALUE,MCO1PinFreq_Value,MSI_VALUE,PLLN,PLLPoutputFreq_Value,PLLQoutputFreq_Value,PLLRCLKFreq_Value,PLLSAI1N,PLLSAI1PoutputFreq_Value,PLLSAI1QoutputFreq_Value,PLLSAI1RoutputFreq_Value,PREFETCH_ENABLE,PWRFreq_Value,RCC_MCO1Source,RNGFreq_Value,RTCClockSelection,RTCFreq_Value,SAI1Freq_Value,SWPMI1Freq_Value,SYSCLKFreq_VALUE,SYSCLKSource,USART1Freq_Value,USART2Freq_Value,USART3CLockSelection,USART3Freq_Value,USBFreq_Value,VCOInputFreq_Value,VCOOutputFreq_Value,VCOSAI1OutputFreq_Value
 RCC.LCDFreq_Value=32768
 RCC.LPTIM1Freq_Value=48000000
 RCC.LPTIM2Freq_Value=48000000
@@ -509,7 +510,8 @@ RCC.SYSCLKFreq_VALUE=48000000
 RCC.SYSCLKSource=RCC_SYSCLKSOURCE_PLLCLK
 RCC.USART1Freq_Value=48000000
 RCC.USART2Freq_Value=48000000
-RCC.USART3Freq_Value=48000000
+RCC.USART3CLockSelection=RCC_USART3CLKSOURCE_HSI
+RCC.USART3Freq_Value=16000000
 RCC.USBFreq_Value=48000000
 RCC.VCOInputFreq_Value=4000000
 RCC.VCOOutputFreq_Value=96000000

From 631953cc30f88926f2d9cd30eb20a3489f4aceb3 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sat, 22 Feb 2020 19:12:12 -0600
Subject: [PATCH 06/36] Revert change to 80MHz in OpenOCD config.

---
 stlink-tnc3.cfg | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/stlink-tnc3.cfg b/stlink-tnc3.cfg
index 37aaca1..adcea77 100644
--- a/stlink-tnc3.cfg
+++ b/stlink-tnc3.cfg
@@ -9,5 +9,4 @@ source [find target/stm32l4x.cfg]
 
 reset_config srst_only
 itm port 0 on
-tpiu config internal swv uart off 80000000
-
+tpiu config internal swv uart off 48000000

From 79f145ccd968109ce6cf49ba5eb2e81078a03f18 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sat, 22 Feb 2020 19:35:11 -0600
Subject: [PATCH 07/36] Fix AFSK modem after FSK changes. Revert changes to
 DigitalPLL.  Remove intrusive diagnostics in AudioInput, along with dead
 code.  Clean up FIR filter code.  Add initial passall support.  Disable LSCO
 when transmitting in debug mode.  Set fixed mid-range DAC output in FSK
 modulator when not transmitting to eliminate DC offset.  New way to compute
 IDLE bytes for TX Delay.  Clean up HDLC decoder, improve HDLC diagnostics,
 add Passall support.  Add new extended response types for modem support. 
 Update API version to 0x0201.  Update firmware version to 2.0.0b1.

---
 TNC/AFSKModulator.hpp       |  78 +++++++--
 TNC/AFSKTestTone.cpp        |   1 +
 TNC/Afsk1200Demodulator.cpp |  62 +++++++
 TNC/Afsk1200Demodulator.hpp |  75 ++------
 TNC/AfskDemodulator.cpp     |   2 +-
 TNC/AfskDemodulator.hpp     |   4 +-
 TNC/AudioInput.cpp          | 149 ----------------
 TNC/AudioLevel.cpp          |   1 +
 TNC/DCD.cpp                 |   1 +
 TNC/Demodulator.cpp         |   9 +
 TNC/Demodulator.hpp         |  17 +-
 TNC/DigitalPLL.hpp          |  16 +-
 TNC/FilterCoefficients.hpp  |   7 +-
 TNC/FirFilter.hpp           |  22 +--
 TNC/Fsk9600Demodulator.cpp  |   2 +-
 TNC/Fsk9600Demodulator.hpp  |  11 +-
 TNC/Fsk9600Modulator.hpp    |  74 ++++++--
 TNC/HDLCEncoder.hpp         |  26 ++-
 TNC/HdlcDecoder.cpp         |  94 +++++-----
 TNC/HdlcDecoder.hpp         | 335 ++----------------------------------
 TNC/IOEventTask.cpp         |   3 +-
 TNC/KissHardware.cpp        | 140 ++++++++-------
 TNC/KissHardware.hpp        | 103 ++++++-----
 TNC/Modulator.hpp           |  39 +++++
 TNC/ModulatorTask.cpp       |  16 +-
 TNC/ModulatorTask.hpp       |  22 ++-
 26 files changed, 532 insertions(+), 777 deletions(-)

diff --git a/TNC/AFSKModulator.hpp b/TNC/AFSKModulator.hpp
index e95456f..c3b5480 100644
--- a/TNC/AFSKModulator.hpp
+++ b/TNC/AFSKModulator.hpp
@@ -1,4 +1,4 @@
-// Copyright 2015-2019 Mobilinkd LLC <rob@mobilinkd.com>
+// Copyright 2015-2020 Mobilinkd LLC <rob@mobilinkd.com>
 // All rights reserved.
 
 #pragma once
@@ -75,7 +75,7 @@ struct AFSKModulator : Modulator
     PTT* ptt_;
     uint8_t twist_{50};
     uint16_t volume_{4096};
-    uint16_t buffer_[DAC_BUFFER_LEN];
+    std::array<uint16_t, DAC_BUFFER_LEN> buffer_;
 
     AFSKModulator(osMessageQId queue, PTT* ptt)
     : dacOutputQueueHandle_(queue), ptt_(ptt)
@@ -88,13 +88,28 @@ struct AFSKModulator : Modulator
    {
        set_twist(hw.tx_twist);
 
-       // Configure 80MHz clock for 26.4ksps.
-       htim7.Init.Period = 3029;
+       // Configure 48MHz clock for 26.4ksps.
+       htim7.Init.Period = 1817;
        if (HAL_TIM_Base_Init(&htim7) != HAL_OK)
        {
            ERROR("htim7 init failed");
            CxxErrorHandler();
        }
+
+       DAC_ChannelConfTypeDef sConfig;
+
+       sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
+       sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
+       sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
+       sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
+       sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
+       if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)
+       {
+         CxxErrorHandler();
+       }
+
+       if (HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_1, DAC_ALIGN_12B_R, 2048) != HAL_OK) CxxErrorHandler();
+       if (HAL_DAC_Start(&hdac1, DAC_CHANNEL_1) != HAL_OK) CxxErrorHandler();
    }
 
    void deinit() override
@@ -120,19 +135,21 @@ struct AFSKModulator : Modulator
 
     void set_twist(uint8_t twist) {twist_ = twist;}
 
-   void send(bool bit) override
-   {
+    void send(bool bit) override
+    {
         switch (running_) {
         case -1:
+            ptt_->on();
+            #ifdef KISS_LOGGING
+                HAL_RCCEx_DisableLSCO();
+            #endif
             fill_first(bit);
             running_ = 0;
             break;
         case 0:
             fill_last(bit);
             running_ = 1;
-            ptt_->on();
-            HAL_TIM_Base_Start(&htim7);
-            HAL_DAC_Start_DMA(&hdac1, DAC_CHANNEL_1, (uint32_t*) buffer_, DAC_BUFFER_LEN, DAC_ALIGN_12B_R);
+            start_conversion();
             break;
         case 1:
             osMessagePut(dacOutputQueueHandle_, bit, osWaitForever);
@@ -171,12 +188,12 @@ struct AFSKModulator : Modulator
 
     void fill_first(bool bit) override
     {
-        fill(buffer_, bit);
+        fill(buffer_.data(), bit);
     }
 
     void fill_last(bool bit) override
     {
-        fill(buffer_ + BIT_LEN, bit);
+        fill(buffer_.data() + BIT_LEN, bit);
     }
 
     void empty() override
@@ -187,10 +204,12 @@ struct AFSKModulator : Modulator
             break;
         case 0:
             running_ = -1;
-            HAL_DAC_Stop_DMA(&hdac1, DAC_CHANNEL_1);
-            HAL_TIM_Base_Stop(&htim7);
+            stop_conversion();
             ptt_->off();
             pos_ = 0;
+            #ifdef KISS_LOGGING
+                HAL_RCCEx_EnableLSCO(RCC_LSCOSOURCE_LSE);
+            #endif
             break;
         case -1:
             break;
@@ -200,10 +219,12 @@ struct AFSKModulator : Modulator
     void abort() override
     {
         running_ = -1;
-        HAL_DAC_Stop_DMA(&hdac1, DAC_CHANNEL_1);
-        HAL_TIM_Base_Stop(&htim7);
+        stop_conversion();
         ptt_->off();
         pos_ = 0;
+        #ifdef KISS_LOGGING
+            HAL_RCCEx_EnableLSCO(RCC_LSCOSOURCE_LSE);
+        #endif
 
         // Drain the queue.
         while (osMessageGet(dacOutputQueueHandle_, 0).status == osEventMessage);
@@ -213,6 +234,33 @@ struct AFSKModulator : Modulator
    {
        return 1.2f;
    }
+
+private:
+   /**
+    * Configure the DAC for timer-based DMA conversion, start the timer,
+    * and start DMA to DAC.
+    */
+   void start_conversion()
+   {
+       DAC_ChannelConfTypeDef sConfig;
+
+       sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
+       sConfig.DAC_Trigger = DAC_TRIGGER_T7_TRGO;
+       sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
+       sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
+       sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
+       if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)
+       {
+         CxxErrorHandler();
+       }
+
+       HAL_TIM_Base_Start(&htim7);
+       HAL_DAC_Start_DMA(
+           &hdac1, DAC_CHANNEL_1,
+           reinterpret_cast<uint32_t*>(buffer_.data()), buffer_.size(),
+           DAC_ALIGN_12B_R);
+   }
+
 };
 
 }} // mobilinkd::tnc
diff --git a/TNC/AFSKTestTone.cpp b/TNC/AFSKTestTone.cpp
index 16db756..483bdac 100644
--- a/TNC/AFSKTestTone.cpp
+++ b/TNC/AFSKTestTone.cpp
@@ -3,6 +3,7 @@
 
 #include "AFSKTestTone.hpp"
 #include "ModulatorTask.hpp"
+#include "Modulator.hpp"
 
 void startAfskToneTask(void const* arg)
 {
diff --git a/TNC/Afsk1200Demodulator.cpp b/TNC/Afsk1200Demodulator.cpp
index f9fe4d0..ccbef19 100644
--- a/TNC/Afsk1200Demodulator.cpp
+++ b/TNC/Afsk1200Demodulator.cpp
@@ -15,6 +15,68 @@ afsk1200::Demodulator Afsk1200Demodulator::demod1(26400, Afsk1200Demodulator::fi
 afsk1200::Demodulator Afsk1200Demodulator::demod2(26400, Afsk1200Demodulator::filter_2);
 afsk1200::Demodulator Afsk1200Demodulator::demod3(26400, Afsk1200Demodulator::filter_3);
 
+hdlc::IoFrame* Afsk1200Demodulator::operator()(const q15_t* samples)
+{
+    hdlc::IoFrame* result = nullptr;
+
+    q15_t* filtered = demod_filter.filter(const_cast<q15_t* >(samples));
+
+    ++counter;
+
+#if 1
+    auto frame1 = demod1(filtered, ADC_BLOCK_SIZE);
+    if (frame1)
+    {
+        if (frame1->fcs() != last_fcs or counter > last_counter + 2)
+        {
+            last_fcs = frame1->fcs();
+            last_counter = counter;
+            result = frame1;
+        }
+        else
+        {
+            hdlc::release (frame1);
+        }
+    }
+#endif
+
+#if 1
+    auto frame2 = demod2(filtered, ADC_BLOCK_SIZE);
+    if (frame2)
+    {
+        if (frame2->fcs() != last_fcs or counter > last_counter + 2)
+        {
+            last_fcs = frame2->fcs();
+            last_counter = counter;
+            result = frame2;
+        }
+        else
+        {
+            hdlc::release(frame2);
+        }
+    }
+#endif
+
+#if 1
+    auto frame3 = demod3(filtered, ADC_BLOCK_SIZE);
+    if (frame3)
+    {
+        if (frame3->fcs() != last_fcs or counter > last_counter + 2)
+        {
+            last_fcs = frame3->fcs();
+            last_counter = counter;
+            result = frame3;
+        }
+        else
+        {
+            hdlc::release(frame3);
+        }
+    }
+#endif
+    locked_ = demod1.locked() or demod2.locked() or demod3.locked();
+    return result;
+}
+
 /*
  * Return twist as a the difference in dB between mark and space.  The
  * expected values are about 0dB for discriminator output and about 5.5dB
diff --git a/TNC/Afsk1200Demodulator.hpp b/TNC/Afsk1200Demodulator.hpp
index 7377099..57dd59f 100644
--- a/TNC/Afsk1200Demodulator.hpp
+++ b/TNC/Afsk1200Demodulator.hpp
@@ -35,14 +35,15 @@ struct Afsk1200Demodulator : IDemodulator
      */
     static constexpr size_t FILTER_TAP_NUM = 132;
     static constexpr uint32_t ADC_BLOCK_SIZE = afsk1200::ADC_BUFFER_SIZE;
-    static constexpr uint32_t SAMPLE_RATE = 26400;
     static_assert(audio::ADC_BUFFER_SIZE >= ADC_BLOCK_SIZE);
 
+    static constexpr uint32_t SAMPLE_RATE = 26400;
+    static constexpr uint16_t VREF = 16383;
+
     using audio_filter_t = Q15FirFilter<ADC_BLOCK_SIZE, FILTER_TAP_NUM>;
 
     static const q15_t bpf_coeffs[FILTER_TAP_NUM];
 
-
     static afsk1200::emphasis_filter_type filter_1;
     static afsk1200::emphasis_filter_type filter_2;
     static afsk1200::emphasis_filter_type filter_3;
@@ -76,6 +77,7 @@ struct Afsk1200Demodulator : IDemodulator
         counter = 0;
 
         demod_filter.init(bpf_coeffs);
+        passall(kiss::settings().options & KISS_OPTION_PASSALL);
 
         hadc1.Init.OversamplingMode = ENABLE;
         if (HAL_ADC_Init(&hadc1) != HAL_OK)
@@ -103,67 +105,7 @@ struct Afsk1200Demodulator : IDemodulator
         locked_ = false;
     }
 
-    hdlc::IoFrame* operator()(const q15_t* samples) override
-    {
-        hdlc::IoFrame* result = nullptr;
-
-        q15_t* filtered = demod_filter(const_cast<q15_t* >(samples));
-
-        ++counter;
-
-#if 1
-        auto frame1 = demod1(filtered, ADC_BLOCK_SIZE);
-        if (frame1)
-        {
-            if (frame1->fcs() != last_fcs or counter > last_counter + 2)
-            {
-                last_fcs = frame1->fcs();
-                last_counter = counter;
-                result = frame1;
-            }
-            else
-            {
-                hdlc::release (frame1);
-            }
-        }
-#endif
-
-#if 1
-        auto frame2 = demod2(filtered, ADC_BLOCK_SIZE);
-        if (frame2)
-        {
-            if (frame2->fcs() != last_fcs or counter > last_counter + 2)
-            {
-                last_fcs = frame2->fcs();
-                last_counter = counter;
-                result = frame2;
-            }
-            else
-            {
-                hdlc::release(frame2);
-            }
-        }
-#endif
-
-#if 1
-        auto frame3 = demod3(filtered, ADC_BLOCK_SIZE);
-        if (frame3)
-        {
-            if (frame3->fcs() != last_fcs or counter > last_counter + 2)
-            {
-                last_fcs = frame3->fcs();
-                last_counter = counter;
-                result = frame3;
-            }
-            else
-            {
-                hdlc::release(frame3);
-            }
-        }
-#endif
-        locked_ = demod1.locked() or demod2.locked() or demod3.locked();
-        return result;
-    }
+    hdlc::IoFrame* operator()(const q15_t* samples) override;
 
     float readTwist() override;
 
@@ -176,6 +118,13 @@ struct Afsk1200Demodulator : IDemodulator
     {
         return ADC_BLOCK_SIZE;
     }
+
+    void passall(bool enable) override
+    {
+        demod1.hdlc_decoder_.passall = enable;
+        demod2.hdlc_decoder_.passall = enable;
+        demod3.hdlc_decoder_.passall = enable;
+    }
 };
 
 }} // mobilinkd::tnc
diff --git a/TNC/AfskDemodulator.cpp b/TNC/AfskDemodulator.cpp
index e520852..d4dba76 100644
--- a/TNC/AfskDemodulator.cpp
+++ b/TNC/AfskDemodulator.cpp
@@ -1,4 +1,4 @@
-// Copyright 2017-2019 Rob Riggs <rob@mobilinkd.com>
+// Copyright 2017-2020 Rob Riggs <rob@mobilinkd.com>
 // All rights reserved.
 
 #include "AfskDemodulator.hpp"
diff --git a/TNC/AfskDemodulator.hpp b/TNC/AfskDemodulator.hpp
index 4769417..73e442a 100644
--- a/TNC/AfskDemodulator.hpp
+++ b/TNC/AfskDemodulator.hpp
@@ -48,11 +48,11 @@ struct Demodulator {
     emphasis_filter_type& audio_filter_;
     libafsk::FixedDelayLine<40> delay_line_;
     DPLL pll_;
-    Q15FirFilter<audio::ADC_BUFFER_SIZE, LPF_FILTER_LEN> lpf_filter_;
+    Q15FirFilter<ADC_BUFFER_SIZE, LPF_FILTER_LEN> lpf_filter_;
     libafsk::NRZI nrzi_;
     hdlc::NewDecoder hdlc_decoder_;
     bool locked_;
-    q15_t buffer_[audio::ADC_BUFFER_SIZE];
+    q15_t buffer_[ADC_BUFFER_SIZE];
 
     Demodulator(size_t sample_rate, emphasis_filter_type& c)
     : sample_rate_(sample_rate)
diff --git a/TNC/AudioInput.cpp b/TNC/AudioInput.cpp
index 2bbe632..042f93a 100644
--- a/TNC/AudioInput.cpp
+++ b/TNC/AudioInput.cpp
@@ -176,8 +176,6 @@ void demodulatorTask() {
             continue;
         }
 
-        gpio::BAT_DIVIDER::off();
-
         auto block = (adc_pool_type::chunk_type*) evt.value.p;
         auto samples = (int16_t*) block->buffer;
 
@@ -201,7 +199,6 @@ void demodulatorTask() {
                 dcd_off();
             }
         }
-        gpio::BAT_DIVIDER::on();
     }
 
     demodulator->stop();
@@ -412,152 +409,6 @@ void pollInputTwist()
     DEBUG("exit pollInputTwist");
 }
 
-#if 0
-void streamAverageInputTwist()
-{
-    DEBUG("enter streamAverageInputTwist");
-
-    constexpr uint32_t channel = AUDIO_IN;
-
-    startADC(channel);
-
-    uint32_t acount = 0;
-    float g700 = 0.0f;
-    float g1200 = 0.0f;
-    float g1700 = 0.0f;
-    float g2200 = 0.0f;
-    float g2700 = 0.0f;
-
-    GoertzelFilter<TWIST_SAMPLE_SIZE, 26400> gf700(700.0);
-    GoertzelFilter<TWIST_SAMPLE_SIZE, 26400> gf1200(1200.0);
-    GoertzelFilter<TWIST_SAMPLE_SIZE, 26400> gf1700(1700.0);
-    GoertzelFilter<TWIST_SAMPLE_SIZE, 26400> gf2200(2200.0);
-    GoertzelFilter<TWIST_SAMPLE_SIZE, 26400> gf2700(2700.0);
-
-    while (true) {
-      osEvent peek = osMessagePeek(audioInputQueueHandle, 0);
-      if (peek.status == osEventMessage) break;
-
-      acount++;
-      uint32_t count = 0;
-      while (count < TWIST_SAMPLE_SIZE) {
-
-          osEvent evt = osMessageGet(adcInputQueueHandle, osWaitForever);
-          if (evt.status != osEventMessage) continue;
-
-          count += ADC_BUFFER_SIZE;
-
-          auto block = (adc_pool_type::chunk_type*) evt.value.v;
-          uint16_t* data =  (uint16_t*) block->buffer;
-          gf700(data, ADC_BUFFER_SIZE);
-          gf1200(data, ADC_BUFFER_SIZE);
-          gf1700(data, ADC_BUFFER_SIZE);
-          gf2200(data, ADC_BUFFER_SIZE);
-          gf2700(data, ADC_BUFFER_SIZE);
-
-          adcPool.deallocate(block);
-      }
-
-      g700 += 10.0 * log10(gf700);
-      g1200 += 10.0 * log10(gf1200);
-      g1700 += 10.0 * log10(gf1700);
-      g2200 += 10.0 * log10(gf2200);
-      g2700 += 10.0 * log10(gf2700);
-
-      char* buffer = 0;
-      // @TODO: Make re-entrant printf work (or convert to fixed-point).
-      int len = asiprintf_r(
-        &buffer,
-        "_%f, %f, %f, %f, %f\r\n",
-        g700 / acount,
-        g1200 / acount,
-        g1700 / acount,
-        g2200 / acount,
-        g2700 / acount);
-
-      if (len > 0) {
-        buffer[0] = kiss::hardware::POLL_INPUT_TWIST;
-        ioport->write((uint8_t*)buffer, len - 1, 6, 10);
-        free(buffer);
-      }
-
-      gf700.reset();
-      gf1200.reset();
-      gf1700.reset();
-      gf2200.reset();
-      gf2700.reset();
-    }
-
-    stopADC();
-    DEBUG("exit streamAverageInputTwist");
-}
-
-void streamInstantInputTwist()
-{
-    DEBUG("enter streamInstantInputTwist");
-
-    constexpr uint32_t channel = AUDIO_IN;
-
-    startADC(channel);
-
-    GoertzelFilter<TWIST_SAMPLE_SIZE, 26400> gf700(700.0);
-    GoertzelFilter<TWIST_SAMPLE_SIZE, 26400> gf1200(1200.0);
-    GoertzelFilter<TWIST_SAMPLE_SIZE, 26400> gf1700(1700.0);
-    GoertzelFilter<TWIST_SAMPLE_SIZE, 26400> gf2200(2200.0);
-    GoertzelFilter<TWIST_SAMPLE_SIZE, 26400> gf2700(2700.0);
-
-    while (true) {
-      osEvent peek = osMessagePeek(audioInputQueueHandle, 0);
-      if (peek.status == osEventMessage) break;
-
-      uint32_t count = 0;
-      while (count < TWIST_SAMPLE_SIZE) {
-
-          osEvent evt = osMessageGet(adcInputQueueHandle, osWaitForever);
-          if (evt.status != osEventMessage) continue;
-
-          count += ADC_BUFFER_SIZE;
-
-          auto block = (adc_pool_type::chunk_type*) evt.value.v;
-          uint16_t* data =  (uint16_t*) block->buffer;
-          gf700(data, ADC_BUFFER_SIZE);
-          gf1200(data, ADC_BUFFER_SIZE);
-          gf1700(data, ADC_BUFFER_SIZE);
-          gf2200(data, ADC_BUFFER_SIZE);
-          gf2700(data, ADC_BUFFER_SIZE);
-
-          adcPool.deallocate(block);
-      }
-
-      char* buffer = 0;
-      // @TODO: Make re-entrant printf work (or convert to fixed-point).
-      int len = asiprintf_r(
-        &buffer,
-        "_%f, %f, %f, %f, %f\r\n",
-        10.0 * log10(gf700),
-        10.0 * log10(gf1200),
-        10.0 * log10(gf1700),
-        10.0 * log10(gf2200),
-        10.0 * log10(gf2700));
-
-      if (len > 0) {
-        buffer[0] = kiss::hardware::POLL_INPUT_TWIST;
-        ioport->write((uint8_t*)buffer, len - 1, 6, 10);
-        free(buffer);
-      }
-
-      gf700.reset();
-      gf1200.reset();
-      gf1700.reset();
-      gf2200.reset();
-      gf2700.reset();
-    }
-
-    stopADC();
-    DEBUG("exit streamInstantInputTwist");
-}
-#endif
-
 void streamAmplifiedInputLevels() {
     DEBUG("enter streamAmplifiedInputLevels");
     streamLevels(AUDIO_IN, kiss::hardware::POLL_INPUT_LEVEL);
diff --git a/TNC/AudioLevel.cpp b/TNC/AudioLevel.cpp
index 096fb25..5c8ad92 100644
--- a/TNC/AudioLevel.cpp
+++ b/TNC/AudioLevel.cpp
@@ -5,6 +5,7 @@
 #include "AudioInput.hpp"
 #include "KissHardware.hpp"
 #include "ModulatorTask.hpp"
+#include "Modulator.hpp"
 #include "GPIO.hpp"
 #include "LEDIndicator.h"
 #include "ModulatorTask.hpp"
diff --git a/TNC/DCD.cpp b/TNC/DCD.cpp
index f1b413e..9dc3733 100644
--- a/TNC/DCD.cpp
+++ b/TNC/DCD.cpp
@@ -3,6 +3,7 @@
 
 #include "DCD.h"
 #include "LEDIndicator.h"
+#include "GPIO.hpp"
 
 bool& dcd_status()
 {
diff --git a/TNC/Demodulator.cpp b/TNC/Demodulator.cpp
index 7fffc5e..4aa2bd7 100644
--- a/TNC/Demodulator.cpp
+++ b/TNC/Demodulator.cpp
@@ -41,4 +41,13 @@ void IDemodulator::startADC(uint32_t period, uint32_t block_size)
     }
 }
 
+void IDemodulator::stopADC()
+{
+    if (HAL_ADC_Stop_DMA(&hadc1) != HAL_OK)
+        CxxErrorHandler();
+    if (HAL_TIM_Base_Stop(&htim6) != HAL_OK)
+        CxxErrorHandler();
+}
+
+
 }} // mobilinkd::tnc
diff --git a/TNC/Demodulator.hpp b/TNC/Demodulator.hpp
index 9eb2b3c..a7ab9ec 100644
--- a/TNC/Demodulator.hpp
+++ b/TNC/Demodulator.hpp
@@ -28,16 +28,21 @@ struct IDemodulator
     virtual bool locked() const = 0;
     virtual size_t size() const = 0;
 
+    /**
+     * Tell the demodulator to return all "passable" HDLC frames.  These
+     * are frames which consist of an even multiple of eight bits and are
+     * up to 330 bytes, but which do not have a valid checksum.
+     *
+     * @param enable is true when enabled and false when disabled.  The
+     *  default state is disabled.
+     */
+    virtual void passall(bool enable) = 0;
+
     virtual ~IDemodulator() {}
 
     static void startADC(uint32_t period, uint32_t block_size);
 
-    static void stopADC() {
-        if (HAL_ADC_Stop_DMA(&hadc1) != HAL_OK)
-            CxxErrorHandler();
-        if (HAL_TIM_Base_Stop(&htim6) != HAL_OK)
-            CxxErrorHandler();
-    }
+    static void stopADC();
 };
 
 }} // mobilinkd::tnc
diff --git a/TNC/DigitalPLL.hpp b/TNC/DigitalPLL.hpp
index 13a73a9..5f3b8b2 100644
--- a/TNC/DigitalPLL.hpp
+++ b/TNC/DigitalPLL.hpp
@@ -1,5 +1,7 @@
-#ifndef MOBILINKD__DIGITAL_PLL_H_
-#define MOBILINKD__DIGITAL_PLL_H_
+// Copyright 2015-2020 Mobilinkd LLC <rob@mobilinkd.com>
+// All rights reserved.
+
+#pragma once
 
 #include "Hysteresis.hpp"
 #include "IirFilter.hpp"
@@ -43,8 +45,7 @@ constexpr std::array<float, 5> lock_a = {
 //
 constexpr std::array<float, 7> loop_coeffs = {
 //     0.08160962754214955, 0.25029850550446403, 0.3361837339067726, 0.2502985055044641, 0.08160962754214969
-//    3.196252e-02,1.204223e-01,2.176819e-01,2.598666e-01,2.176819e-01,1.204223e-01,3.196252e-02
-    0.0, 0.0, 0.5, 0.5, 0.0, 0.0, 0.0
+    3.196252e-02,1.204223e-01,2.176819e-01,2.598666e-01,2.176819e-01,1.204223e-01,3.196252e-02
 };
 
 } // pll
@@ -73,8 +74,8 @@ struct BaseDigitalPLL
 	BaseDigitalPLL(float_type sample_rate, float_type symbol_rate)
 	: sample_rate_(sample_rate), symbol_rate_(symbol_rate)
 	, sps_(sample_rate / symbol_rate)
-	, limit_(sps_ / float_type(2.0))
-    , lock_(sps_ * float_type(0.03), sps_ * float_type(0.15), 1, 0)
+    , limit_(sps_ / 2.0)
+    , lock_(sps_ * 0.03, sps_ * 0.15, 1, 0)
 	, last_(false), count_(0), sample_(false)
 	, jitter_(0.0), bits_(1)
 	{}
@@ -128,6 +129,3 @@ typedef BaseDigitalPLL<double> DigitalPLL;
 typedef BaseDigitalPLL<float> FastDigitalPLL;
 
 }} // mobilinkd::tnc
-
-#endif // MOBILINKD__DIGITAL_PLL_H_
-
diff --git a/TNC/FilterCoefficients.hpp b/TNC/FilterCoefficients.hpp
index f422526..e24466a 100644
--- a/TNC/FilterCoefficients.hpp
+++ b/TNC/FilterCoefficients.hpp
@@ -1,8 +1,7 @@
-// Copyright 2015 Rob Riggs <rob@mobilinkd.com>
+// Copyright 2015-2020 Rob Riggs <rob@mobilinkd.com>
 // All rights reserved.
 
-#ifndef MOBILINKD__TNC__FILTER_COEFFICIENTS_HPP_
-#define MOBILINKD__TNC__FILTER_COEFFICIENTS_HPP_
+#pragma once
 
 #include "IirFilter.hpp"
 #include "FirFilter.hpp"
@@ -303,5 +302,3 @@ extern const TFirCoefficients<9>* AfskFilters[19];
 
 
 }}} // mobilinkd::tnc::filter
-
-#endif // MOBILINKD__TNC__FILTER_COEFFICIENTS_HPP_
diff --git a/TNC/FirFilter.hpp b/TNC/FirFilter.hpp
index 5ec221d..8f64ae5 100644
--- a/TNC/FirFilter.hpp
+++ b/TNC/FirFilter.hpp
@@ -1,8 +1,7 @@
-// Copyright 2015-2019 Rob Riggs <rob@mobilinkd.com>
+// Copyright 2015-2020 Rob Riggs <rob@mobilinkd.com>
 // All rights reserved.
 
-#ifndef MOBILINKD__TNC__FIR_FILTER_H_
-#define MOBILINKD__TNC__FIR_FILTER_H_
+#pragma once
 
 #include <AudioLevel.hpp>
 
@@ -114,25 +113,16 @@ struct Q15FirFilter {
     {
         vgnd_ = audio::virtual_ground;
         filter_taps = taps;
-        arm_fir_init_q15(&instance, FILTER_SIZE, const_cast<q15_t*>(filter_taps), // WTF ARM?!?
+        arm_fir_init_q15(&instance, FILTER_SIZE,
+            const_cast<q15_t*>(filter_taps),
             filter_state, BLOCK_SIZE);
     }
 
-    // ADC input
-    q15_t* operator()(q15_t* input) // __attribute__((section(".bss2")))
+    q15_t* filter(const q15_t* input)
     {
-        arm_fir_fast_q15(&instance, input, filter_output, BLOCK_SIZE);
-        return filter_output;
-    }
-
-    // LPF input
-    q15_t* filter(q15_t* input) // __attribute__((section(".bss2")))
-    {
-        arm_fir_fast_q15(&instance, input, filter_output, BLOCK_SIZE);
+        arm_fir_fast_q15(&instance, const_cast<q15_t*>(input), filter_output, BLOCK_SIZE);
         return filter_output;
     }
 };
 
 }} // mobilinkd::tnc
-
-#endif // MOBILINKD__TNC__FIR_FILTER_H_
diff --git a/TNC/Fsk9600Demodulator.cpp b/TNC/Fsk9600Demodulator.cpp
index 2c94cc6..8ec4ecb 100644
--- a/TNC/Fsk9600Demodulator.cpp
+++ b/TNC/Fsk9600Demodulator.cpp
@@ -11,7 +11,7 @@ hdlc::IoFrame* Fsk9600Demodulator::operator()(const q15_t* samples)
 {
     hdlc::IoFrame* result = nullptr;
 
-    auto filtered = demod_filter(const_cast<q15_t* >(samples));
+    auto filtered = demod_filter.filter(const_cast<q15_t* >(samples));
 
     for (size_t i = 0; i != ADC_BLOCK_SIZE; ++i)
     {
diff --git a/TNC/Fsk9600Demodulator.hpp b/TNC/Fsk9600Demodulator.hpp
index c2b1dc7..880ed51 100644
--- a/TNC/Fsk9600Demodulator.hpp
+++ b/TNC/Fsk9600Demodulator.hpp
@@ -55,17 +55,13 @@ struct Fsk9600Demodulator : IDemodulator
         auto const& bpf_coeffs = bpf_bank[kiss::settings().rx_twist + 3];
         const q15_t* bpf = bpf_coeffs.data();
         demod_filter.init(bpf);
+        passall(kiss::settings().options & KISS_OPTION_PASSALL);
 
         hadc1.Init.OversamplingMode = DISABLE;
         if (HAL_ADC_Init(&hadc1) != HAL_OK)
         {
             CxxErrorHandler();
         }
-//
-//        if (HAL_ADCEx_Calibration_Start(&hadc1, ADC_SINGLE_ENDED) != HAL_OK)
-//        {
-//            CxxErrorHandler();
-//        }
 
         ADC_ChannelConfTypeDef sConfig;
 
@@ -102,6 +98,11 @@ struct Fsk9600Demodulator : IDemodulator
     {
         return ADC_BLOCK_SIZE;
     }
+
+    void passall(bool enable) override
+    {
+        hdlc_decoder_.passall = enable;
+    }
 };
 
 }} // mobilinkd::tnc
diff --git a/TNC/Fsk9600Modulator.hpp b/TNC/Fsk9600Modulator.hpp
index f9e491a..a98ac80 100644
--- a/TNC/Fsk9600Modulator.hpp
+++ b/TNC/Fsk9600Modulator.hpp
@@ -27,6 +27,7 @@ struct Fsk9600Modulator : Modulator
 {
     static constexpr int8_t DAC_BUFFER_LEN = 40;
     static constexpr int8_t BIT_LEN = DAC_BUFFER_LEN / 2;
+    static constexpr uint16_t VREF = 4095;
 
     static constexpr std::array<int16_t, BIT_LEN> cos_table{
         2047,  2020,  1937,  1801,  1616,  1387,  1120,   822,   502,   169,
@@ -54,6 +55,8 @@ struct Fsk9600Modulator : Modulator
     {
         for (auto& x : buffer_) x = 2048;
 
+        (void) hw; // unused
+
         state = State::STOPPED;
         level = Level::HIGH;
 
@@ -64,12 +67,27 @@ struct Fsk9600Modulator : Modulator
             ERROR("htim7 init failed");
             CxxErrorHandler();
         }
+
+        DAC_ChannelConfTypeDef sConfig;
+
+        sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
+        sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
+        sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
+        sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
+        sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
+        if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)
+        {
+          CxxErrorHandler();
+        }
+
+        if (HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_1, DAC_ALIGN_12B_R, 2048) != HAL_OK) CxxErrorHandler();
+        if (HAL_DAC_Start(&hdac1, DAC_CHANNEL_1) != HAL_OK) CxxErrorHandler();
     }
 
     void deinit() override
     {
         state = State::STOPPED;
-        HAL_DAC_Stop_DMA(&hdac1, DAC_CHANNEL_1);
+        HAL_DAC_Stop(&hdac1, DAC_CHANNEL_1);
         HAL_TIM_Base_Stop(&htim7);
         ptt_->off();
     }
@@ -100,18 +118,18 @@ struct Fsk9600Modulator : Modulator
         {
         case State::STOPPING:
         case State::STOPPED:
+            ptt_->on();
+            #ifdef KISS_LOGGING
+                HAL_RCCEx_DisableLSCO();
+            #endif
+
             fill_first(scrambled);
             state = State::STARTING;
             break;
         case State::STARTING:
             fill_last(scrambled);
             state = State::RUNNING;
-            ptt_->on();
-            HAL_TIM_Base_Start(&htim7);
-            HAL_DAC_Start_DMA(
-                &hdac1, DAC_CHANNEL_1,
-                reinterpret_cast<uint32_t*>(buffer_.data()), buffer_.size(),
-                DAC_ALIGN_12B_R);
+            start_conversion();
             break;
         case State::RUNNING:
             osMessagePut(dacOutputQueueHandle_, scrambled, osWaitForever);
@@ -142,24 +160,27 @@ struct Fsk9600Modulator : Modulator
             break;
         case State::STOPPING:
             state = State::STOPPED;
-            HAL_DAC_Stop_DMA(&hdac1, DAC_CHANNEL_1);
-            HAL_TIM_Base_Stop(&htim7);
+            stop_conversion();
             ptt_->off();
+            level = Level::HIGH;
+            #ifdef KISS_LOGGING
+                HAL_RCCEx_EnableLSCO(RCC_LSCOSOURCE_LSE);
+            #endif
             break;
         case State::STOPPED:
             break;
         }
-        state = State::STOPPING;
-        level = Level::HIGH;
     }
 
     void abort() override
     {
         state = State::STOPPED;
-        HAL_DAC_Stop_DMA(&hdac1, DAC_CHANNEL_1);
-        HAL_TIM_Base_Stop(&htim7);
+        stop_conversion();
         ptt_->off();
-
+        level = Level::HIGH;
+        #ifdef KISS_LOGGING
+            HAL_RCCEx_EnableLSCO(RCC_LSCOSOURCE_LSE);
+        #endif
         // Drain the queue.
         while (osMessageGet(dacOutputQueueHandle_, 0).status == osEventMessage);
     }
@@ -171,6 +192,31 @@ struct Fsk9600Modulator : Modulator
 
 private:
 
+    /**
+     * Configure the DAC for timer-based DMA conversion, start the timer,
+     * and start DMA to DAC.
+     */
+    void start_conversion()
+    {
+        DAC_ChannelConfTypeDef sConfig;
+
+        sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
+        sConfig.DAC_Trigger = DAC_TRIGGER_T7_TRGO;
+        sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
+        sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
+        sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
+        if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)
+        {
+          CxxErrorHandler();
+        }
+
+        HAL_TIM_Base_Start(&htim7);
+        HAL_DAC_Start_DMA(
+            &hdac1, DAC_CHANNEL_1,
+            reinterpret_cast<uint32_t*>(buffer_.data()), buffer_.size(),
+            DAC_ALIGN_12B_R);
+    }
+
     uint16_t adjust_level(int32_t sample) const
     {
         sample *= volume_;
diff --git a/TNC/HDLCEncoder.hpp b/TNC/HDLCEncoder.hpp
index 6cf190e..355f679 100644
--- a/TNC/HDLCEncoder.hpp
+++ b/TNC/HDLCEncoder.hpp
@@ -1,10 +1,10 @@
-// Copyright 2015 Mobilinkd LLC <rob@mobilinkd.com>
+// Copyright 2015-2020 Mobilinkd LLC <rob@mobilinkd.com>
 // All rights reserved.
 
-#ifndef INC_HDLCENCODER_HPP_
-#define INC_HDLCENCODER_HPP_
+#pragma once
 
 #include "Modulator.hpp"
+#include "ModulatorTask.hpp"
 #include "HdlcFrame.hpp"
 #include "NRZI.hpp"
 #include "PTT.hpp"
@@ -51,12 +51,12 @@ struct Encoder {
     volatile bool running_;
     bool send_delay_;   // Avoid sending the preamble for back-to-back frames.
 
-    Encoder(osMessageQId input, Modulator* output)
+    Encoder(osMessageQId input)
     : tx_delay_(kiss::settings().txdelay), tx_tail_(kiss::settings().txtail)
     , p_persist_(kiss::settings().ppersist), slot_time_(kiss::settings().slot)
     , duplex_(kiss::settings().duplex), state_(state_type::STATE_IDLE)
     , ones_(0), nrzi_(), crc_()
-    , input_(input), modulator_(output)
+    , input_(input), modulator_(&getModulator())
     , running_(false), send_delay_(true)
    {}
 
@@ -67,11 +67,17 @@ struct Encoder {
             state_ = state_type::STATE_IDLE;
             osEvent evt = osMessageGet(input_, osWaitForever);
             if (evt.status == osEventMessage) {
+                tx_delay_ = kiss::settings().txdelay;
+                tx_tail_ = kiss::settings().txtail;
+                p_persist_ = kiss::settings().ppersist;
+                slot_time_ = kiss::settings().slot;
+                duplex_ = kiss::settings().duplex;
                 auto frame = (IoFrame*) evt.value.p;
                 process(frame);
                 // See if we have back-to-back frames.
                 evt = osMessagePeek(input_, 0);
                 if (evt.status != osEventMessage) {
+                    send_raw(IDLE);
                     send_raw(IDLE);
                     send_delay_ = true;
                     if (!duplex_) {
@@ -95,6 +101,11 @@ struct Encoder {
     int p_persist() const { return p_persist_; }
     void p_persist(int value) { p_persist_ = value; }
 
+    void updateModulator()
+    {
+        modulator_ = &(getModulator());
+    }
+
     state_type status() const {return state_; }
     void stop() { running_ = false; }
 
@@ -192,7 +203,8 @@ struct Encoder {
     }
 
     void send_delay() {
-        const size_t tmp = tx_delay_ * modulator_->bits_per_ms();
+        const size_t tmp = tx_delay_ * 1.25 * modulator_->bits_per_ms();
+        INFO("Sending %u IDLE bytes", tmp);
         for (size_t i = 0; i != tmp; i++) {
             send_raw(IDLE);
         }
@@ -239,5 +251,3 @@ struct Encoder {
 };
 
 }}} // mobilinkd::tnc::hdlc
-
-#endif // INC_HDLCENCODER_HPP_
diff --git a/TNC/HdlcDecoder.cpp b/TNC/HdlcDecoder.cpp
index 789a11f..bce1f31 100644
--- a/TNC/HdlcDecoder.cpp
+++ b/TNC/HdlcDecoder.cpp
@@ -7,48 +7,6 @@
 
 namespace mobilinkd { namespace tnc { namespace hdlc {
 
-Decoder::Decoder(bool pass_all)
-: state_(SEARCH), ones_(0), buffer_(0), frame_(acquire())
-, bits_(0), passall_(pass_all), ready_(false)
-{}
-
-IoFrame* Decoder::operator()(bool bit, bool pll)
-{
-    IoFrame* result = nullptr;
-
-    // It appears that the ioFramePool may not get initialized in the proper
-    // order during some builds.
-    if (nullptr == frame_) frame_ = acquire();
-    if (nullptr == frame_) return result;
-
-    if (not pll) {
-        if ((state_ == FRAMING) and (frame_->size() >= 15) and passall_) {
-            frame_->parse_fcs();
-            if (passall_ or frame_->ok()) {
-                result = frame_;
-                ready_ = false;
-                frame_ = acquire();
-                return result;
-            }
-        }
-        reset();
-    } else {
-        if (process(bit)) {
-            ready_ = false;
-            frame_->parse_fcs();
-            if (passall_ or frame_->ok()) {
-                result = frame_;
-                frame_ = acquire();
-                if (frame_) start_hunt();
-                return result;
-            }
-            frame_->clear();
-        }
-    }
-
-    return result;
-}
-
 NewDecoder::optional_result_type NewDecoder::operator()(bool input, bool pll_lock)
 {
     optional_result_type result = nullptr;
@@ -56,9 +14,8 @@ NewDecoder::optional_result_type NewDecoder::operator()(bool input, bool pll_loc
     auto status = process(input, pll_lock);
     if (status)
     {
-//        INFO("Frame Status = %02x, size = %d, CRC = %04x",
-//            int(status), int(packet->size()), int(packet->crc()));
-        if (((status & STATUS_OK) || passall) && packet->size() > 10)
+        INFO("HDLC decode status = 0x%02x, bits = %d", int(status), int(report_bits));
+        if (can_pass(status) and packet->size() > 10)
         {
             result = packet;
             packet = nullptr;
@@ -74,6 +31,8 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
 {
     uint8_t result_code = 0;
 
+    if (state == State::IDLE and not pll_lock) return result_code;
+
     while (packet == nullptr) {
         packet = ioFramePool().acquire();
         if (!packet) osThreadYield();
@@ -104,9 +63,24 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
         if (flag) {
             switch (buffer) {
             case 0x7E:
-                if (packet->size()) {
+                if (packet->size() > 0) {
+                    // We have started decoding a packet.
                     packet->parse_fcs();
-                    result_code = packet->ok() ? STATUS_OK : STATUS_CRC_ERROR;
+                    report_bits = bits;
+                    if (packet->ok()) {
+                        // CRC is OK, assume a good packet, even if there are
+                        // extraneous bits decoded.
+                        result_code = STATUS_OK;
+                    } else if (bits == 8) {
+                        // Otherwise, if there is a CRC error but we are on
+                        // an even byte boundary, flag a CRC error.  This is
+                        // used by the "pass all" rule.
+                        result_code = STATUS_CRC_ERROR;
+                    } else {
+                        // Extraneous bits mean we have a framing error.
+                        // We should not pass this frame up the stack.
+                        result_code = STATUS_FRAME_ERROR;
+                    }
                 }
                 state = State::SYNC;
                 flag = 0;
@@ -127,7 +101,8 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
             return result_code;
         }
 
-        switch (state) {
+        switch (state)
+        {
 
         case State::IDLE:
             break;
@@ -149,10 +124,29 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
         }
     } else {
         // PLL unlocked.
-        if (packet->size()) {
+        // Note the rules here are the same as above.
+        report_bits = bits;
+        if (packet->size() > 2)
+        {
             packet->parse_fcs();
-            result_code = packet->ok() ? STATUS_OK | STATUS_NO_CARRIER : STATUS_NO_CARRIER;
+            if (packet->ok())
+            {
+                result_code = STATUS_OK;
+            }
+            else if (bits == 8)
+            {
+                result_code = STATUS_CRC_ERROR;
+            }
+            else
+            {
+                result_code = STATUS_NO_CARRIER;
+            }
         }
+        else
+        {
+            result_code = STATUS_NO_CARRIER;
+        }
+
         if (state != State::IDLE) {
             buffer = 0;
             flag = 0;
diff --git a/TNC/HdlcDecoder.hpp b/TNC/HdlcDecoder.hpp
index ce6e746..82ac73e 100644
--- a/TNC/HdlcDecoder.hpp
+++ b/TNC/HdlcDecoder.hpp
@@ -1,8 +1,7 @@
-// Copyright 2015-2019 Mobilinkd LLC <rob@mobilinkd.com>
+// Copyright 2015-2020 Mobilinkd LLC <rob@mobilinkd.com>
 // All rights reserved.
 
-#ifndef MOBILINKD___HDLC_DECODER_HPP_
-#define MOBILINKD___HDLC_DECODER_HPP_
+#pragma once
 
 #include "HdlcFrame.hpp"
 
@@ -10,320 +9,6 @@
 
 namespace mobilinkd { namespace tnc { namespace hdlc {
 
-struct Decoder
-{
-    static const uint16_t FLAG = 0x7E00;
-    static const uint16_t ABORT = 0x7F;
-    static const uint16_t IDLE = 0xFF;
-
-    enum state {SEARCH, HUNT, FRAMING};
-
-    state state_;
-    int ones_;
-    uint16_t buffer_;
-    IoFrame* frame_;
-    int bits_;
-    bool passall_;
-    bool ready_;
-
-    Decoder(bool pass_all = false);
-
-    void reset() {
-        state_ = SEARCH;
-        ones_ = 0;
-        buffer_ = 0;
-        if (frame_) frame_->clear();
-        ready_ = false;
-    }
-
-    bool process(bool bit)
-    {
-        switch (state_)
-        {
-        case SEARCH:
-            search(bit);
-            break;
-        case HUNT:
-            hunt(bit);
-            break;
-        case FRAMING:
-            frame(bit);
-            break;
-        default:
-            reset();
-            break;
-        }
-
-        return ready_;
-    }
-
-    /**
-     * Process a bit.  If the bit results in a frame, a result set containing
-     * the frame, the FCS, and a flag indicating whether it is valid is
-     * returned.  If HDLC was contructed with passall=false, the flag returned
-     * is always true as only valid frames are returned.
-     *
-     * When PLL is passed, when true it indicates that the bit should be
-     * processed, and when false indicates that any frame in progress should
-     * be dropped and the state reset to SEARCH.
-     */
-    IoFrame* operator()(bool bit, bool pll);
-
-    void add_bit(bool bit)
-    {
-        const uint16_t BIT = 0x8000;
-
-        buffer_ >>= 1;
-        buffer_ |= (BIT * int(bit));
-        bits_ += 1;
-    }
-
-    char get_char()
-    {
-        char result = (buffer_ & 0xFF);
-
-        return result;
-    }
-
-    void consume_byte()
-    {
-        const uint16_t MASK = 0xFF00;
-
-        buffer_ &= MASK;
-        bits_ -= 8;
-    }
-
-    void consume_bit()
-    {
-        const uint16_t MASK = 0xFF00;
-
-        uint16_t tmp = (buffer_ & 0x7F);
-        tmp <<= 1;
-        buffer_ &= MASK;
-        buffer_ |= tmp;
-        bits_ -= 1;
-    }
-
-    void start_search()
-    {
-        state_ = SEARCH;
-    }
-
-    bool have_flag()
-    {
-        const uint16_t MASK = 0xFF00;
-
-        return (buffer_ & MASK) == FLAG;
-    }
-
-    void start_hunt()
-    {
-        state_ = HUNT;
-        bits_ = 0;
-        buffer_ = 0;
-    }
-
-    void search(bool bit)
-    {
-        add_bit(bit);
-
-        if (have_flag())
-        {
-            start_hunt();
-        }
-    }
-
-    bool have_frame_error()
-    {
-        switch (buffer_ & 0xFF00)
-        {
-        case 0xFF00:
-        case 0xFE00:
-        case 0xFC00:
-        case 0x7F00:
-        case 0x7E00:
-        case 0x3F00:
-            return true;
-        default:
-            return false;
-        }
-    }
-
-    bool have_bogon()
-    {
-        const uint16_t MASK = 0xFF00;
-
-        if  (bits_ != 8) return false;
-
-        const uint16_t test = (buffer_ & MASK);
-
-        switch (test)
-        {
-        case 0xFF00:
-        case 0xFE00:
-        case 0x7F00:
-            return true;
-        default:
-            return false;
-        }
-    }
-
-    void start_frame()
-    {
-        state_ = FRAMING;
-        frame_->clear();
-        ones_ = 0;
-        buffer_ &= 0xFF00;
-    }
-
-    void hunt(bool bit)
-    {
-        const uint16_t MASK = 0xFF00;
-
-        add_bit(bit);
-        buffer_ &= MASK;
-
-        if (bits_ != 8) return;
-
-        if (have_flag())  {
-            start_hunt();
-            return;
-        }
-
-        if (have_bogon()) {
-            start_search();
-            return;
-        }
-
-        if (not have_frame_error())  {
-            start_frame();
-            return;
-        }
-
-        start_search();
-    }
-
-    void frame(bool bit)
-    {
-        add_bit(bit);
-
-        if (ones_ < 5) {
-            if (buffer_ & 0x80) ones_ += 1;
-            else ones_ = 0;
-
-            if (bits_ == 16) {
-                if (frame_->push_back(get_char())) {
-                    consume_byte();
-                } else {
-                    // Allocation error.
-                    frame_->clear();
-                    start_search();
-                }
-            }
-
-            if (have_flag()) {
-                if (frame_->size() >= 15) {
-                    ready_ = true;
-                }
-            }
-        } else {
-            // 5 ones in a row means the next one should be 0 and be skipped.
-
-            if ((buffer_ & 0x80) == 0) {
-                ones_ = 0;
-                consume_bit();
-                return;
-            } else {
-
-                // Framing error.  Drop the frame.  If there is a FLAG
-                // in the buffer, go into HUNT otherwise SEARCH.
-                if (frame_->size() > 15) {
-                    ready_ = true;
-                    return;
-                }
-
-                if ((buffer_ >> (16 - bits_) & 0xFF) == 0x7E) {
-                    // Cannot call start_hunt() here because we need
-                    // to preserve buffer state.
-                    bits_ -= 8;
-                    state_ = HUNT;
-                    frame_->clear();
-                } else {
-                    start_search();
-                }
-            }
-        }
-    }
-
-    bool frame_end()
-    {
-        uint16_t tmp = (buffer_ >> (16 - bits_));
-        return (tmp & 0xFF) == FLAG;
-    }
-
-    bool frame_abort()
-    {
-        uint16_t tmp = (buffer_ >> (16 - bits_));
-        return (tmp & 0x7FFF) == 0x7FFF;
-    }
-
-    void abort_frame()
-    {
-        bits_ = 8;
-        buffer_ &= 0xFF00;
-        frame_->clear();
-    }
-
-    bool ready() const
-    {
-        return ready_;
-    }
-};
-
-#if 0
-
-Decoder::Decoder(bool pass_all)
-: state_(SEARCH), ones_(0), buffer_(0), frame_(acquire())
-, bits_(0), passall_(pass_all), ready_(false)
-{}
-
-IoFrame* Decoder::operator()(bool bit, bool pll)
-{
-    IoFrame* result = nullptr;
-
-    // It appears that the ioFramePool may not get initialized in the proper
-    // order during some builds.
-    if (nullptr == frame_) frame_ = acquire();
-
-    if (not pll) {
-        if ((state_ == FRAMING) and (frame_->size() > 15) and passall_) {
-            frame_->parse_fcs();
-            if (passall_ or frame_->ok()) {
-                result = frame_;
-                ready_ = false;
-                frame_ = acquire();
-                return result;
-            }
-        }
-        reset();
-    } else {
-        if (process(bit)) {
-            ready_ = false;
-            frame_->parse_fcs();
-            if (passall_ or frame_->ok()) {
-                result = frame_;
-                frame_ = acquire();
-                return result;
-            }
-            frame_->clear();
-        }
-    }
-
-    return result;
-}
-#endif
-
-
 struct NewDecoder
 {
     enum class State {IDLE, SYNC, RECEIVE};
@@ -338,15 +23,22 @@ struct NewDecoder
     static constexpr uint8_t STATUS_NO_CARRIER{0x10};
     static constexpr uint8_t STATUS_CRC_ERROR{0x20};
 
-    const uint16_t VALID_CRC = 0xf0b8;
+    static constexpr uint16_t VALID_CRC = 0xf0b8;
 
     State state{State::IDLE};
 
     uint8_t buffer{0};
 
     uint8_t bits{0};
+    uint8_t report_bits{0};
     uint8_t ones{0};
     bool flag{0};
+
+    /**
+     * Tell the demodulator to return all "passable" HDLC frames.  These
+     * are frames which consist of an even multiple of eight bits and are
+     * up to 330 bytes, but which do not have a valid checksum.
+     */
     bool passall{false};
 
     frame_type* packet{nullptr};
@@ -355,10 +47,13 @@ struct NewDecoder
     : passall(pass_all)
     {}
 
+    bool can_pass(uint8_t status) const
+    {
+        return status == STATUS_OK or (passall and status == STATUS_CRC_ERROR);
+    }
+
     optional_result_type operator()(bool input, bool pll_lock);
     uint8_t process(bool input, bool pll_lock);
 };
 
 }}} // mobilinkd::tnc::hdlc
-
-#endif // MOBILINKD___HDLC_DECODER_HPP_
diff --git a/TNC/IOEventTask.cpp b/TNC/IOEventTask.cpp
index ad2792e..69fe5a7 100644
--- a/TNC/IOEventTask.cpp
+++ b/TNC/IOEventTask.cpp
@@ -12,6 +12,7 @@
 #include "Kiss.hpp"
 #include "KissHardware.hpp"
 #include "ModulatorTask.hpp"
+#include "Modulator.hpp"
 #include "UsbPort.hpp"
 #include "SerialPort.hpp"
 #include "NullPort.hpp"
@@ -60,7 +61,6 @@ void startIOEventTask(void const*)
         hardware.init();
         hardware.store();
     }
-//    hardware.init();
 
     osMutexRelease(hardwareInitMutexHandle);
 
@@ -107,7 +107,6 @@ void startIOEventTask(void const*)
             DEBUG("USB connected -- negotiate");
             HAL_GPIO_WritePin(BT_SLEEP_GPIO_Port, BT_SLEEP_Pin,
                 GPIO_PIN_RESET);
-//            SysClock48();
             osTimerStart(usbShutdownTimerHandle, 5000);
         }
     }
diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index 13e29e8..b4669d4 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -6,7 +6,9 @@
 #include "AudioInput.hpp"
 #include "AudioLevel.hpp"
 #include "IOEventTask.h"
-#include <ModulatorTask.hpp>
+#include "ModulatorTask.hpp"
+#include "Modulator.hpp"
+#include "HDLCEncoder.hpp"
 
 #include <memory>
 #include <array>
@@ -27,17 +29,10 @@ int powerOffViaUSB(void)
 
 namespace mobilinkd { namespace tnc { namespace kiss {
 
-const char FIRMWARE_VERSION[] = "2.0.0a1";
+const char FIRMWARE_VERSION[] = "2.0.0b1";
 const char HARDWARE_VERSION[] = "Mobilinkd TNC3 2.1.1";
 
 
-const std::array<const char*, 4> modem_type_lookup = {
-    "NOT SET",
-    "AFSK1200",
-    "AFSK300",
-    "FSK9600",
-};
-
 Hardware& settings()
 {
     static Hardware instance __attribute__((section(".bss3")));
@@ -107,9 +102,7 @@ void Hardware::set_duplex(uint8_t value) {
     update_crc();
 }
 
-#if 1
-
- void reply8(uint8_t cmd, uint8_t result) {
+void reply8(uint8_t cmd, uint8_t result) {
     uint8_t data[2] { cmd, result };
     ioport->write(data, 2, 6, osWaitForever);
 }
@@ -127,17 +120,33 @@ inline void reply(uint8_t cmd, const uint8_t* data, uint16_t len) {
     ioport->write(buffer, len + 1, 6, osWaitForever);
 }
 
-inline void reply_ext(uint8_t ext, uint8_t cmd, const uint8_t* data, uint16_t len) {
-    auto buffer = static_cast<uint8_t*>(alloca(len + 2));
+template <size_t N>
+void reply_ext(const std::array<uint8_t, N>& cmd, const uint8_t* data, uint16_t len) {
+    auto buffer = static_cast<uint8_t*>(alloca(len + N));
     if (buffer == nullptr) return;
-    buffer[0] = ext;
-    buffer[1] = cmd;
+    std::copy(std::begin(cmd), std::end(cmd), buffer);
     for (uint16_t i = 0; i != len and data[i] != 0; i++)
-        buffer[i + 2] = data[i];
+        buffer[i + N] = data[i];
     ioport->write(buffer, len + 2, 6, osWaitForever);
     free(buffer);
 }
-#endif
+
+
+template <size_t N>
+inline void ext_reply(const std::array<uint8_t, N>& cmd, uint8_t result) {
+    std::array<uint8_t, 1 + N> buffer;
+    std::copy(std::begin(cmd), std::end(cmd), std::begin(buffer));
+    buffer[N] = result;
+    ioport->write(buffer.data(), N + 1, 6, osWaitForever);
+}
+
+template <size_t M, size_t N>
+void ext_reply(const std::array<uint8_t, M>& cmd, const std::array<uint8_t, N>& result) {
+    std::array<uint8_t, M + N> data;
+    std::copy(std::begin(cmd), std::end(cmd), std::begin(data));
+    std::copy(std::begin(result), std::end(result), std::begin(data) + M);
+    ioport->write(data.data(), M + N, 6, osWaitForever);
+}
 
 void Hardware::get_alias(uint8_t alias) {
     uint8_t result[14];
@@ -149,7 +158,7 @@ void Hardware::get_alias(uint8_t alias) {
     result[11] = aliases[alias].insert_id;
     result[12] = aliases[alias].preempt;
     result[13] = aliases[alias].hops;
-    reply_ext(hardware::EXTENDED_CMD, hardware::EXT_GET_ALIASES, result, 14);
+    reply_ext(hardware::EXT_GET_ALIASES, result, 14);
 }
 
 void Hardware::set_alias(const hdlc::IoFrame* frame) {
@@ -187,14 +196,13 @@ void Hardware::handle_request(hdlc::IoFrame* frame) {
 
     switch (command) {
 
-#if 1
     case hardware::SAVE:
     case hardware::SAVE_EEPROM_SETTINGS:
         update_crc();
         store();
         reply8(hardware::OK, hardware::SAVE_EEPROM_SETTINGS);
         break;
-#endif
+
     case hardware::POLL_INPUT_LEVEL:
         DEBUG("POLL_INPUT_VOLUME");
         reply8(hardware::POLL_INPUT_LEVEL, 0);
@@ -385,26 +393,6 @@ void Hardware::handle_request(hdlc::IoFrame* frame) {
         reply8(hardware::GET_DUPLEX, duplex);
         break;
 
-    case hardware::SET_MODEM_TYPE:
-        DEBUG("SET_MODEM_TYPE");
-        if ((*it > 0) and (*it < 4))
-        {
-            modem_type = *it;
-            DEBUG(modem_type_lookup[*it]);
-            update_crc();
-        }
-        else
-        {
-            ERROR("Unknown modem type");
-        }
-        osMessagePut(audioInputQueueHandle, audio::UPDATE_SETTINGS,
-            osWaitForever);
-        [[fallthrough]];
-    case hardware::GET_MODEM_TYPE:
-        DEBUG("GET_MODEM_TYPE");
-        reply8(hardware::GET_MODEM_TYPE, modem_type);
-        break;
-
     case hardware::GET_FIRMWARE_VERSION:
         DEBUG("GET_FIRMWARE_VERSION");
         reply(hardware::GET_FIRMWARE_VERSION, (uint8_t*) FIRMWARE_VERSION,
@@ -440,6 +428,20 @@ void Hardware::handle_request(hdlc::IoFrame* frame) {
             options & KISS_OPTION_PTT_SIMPLEX ? 0 : 1);
         break;
 
+    case hardware::SET_PASSALL:
+        DEBUG("SET_PASSALL");
+        if (!*it) {
+          options &= ~KISS_OPTION_PASSALL;
+        } else {
+          options |= KISS_OPTION_PASSALL;
+        }
+        update_crc();
+        break;
+    case hardware::GET_PASSALL:
+        DEBUG("GET_PASSALL");
+        reply8(hardware::GET_PASSALL, options & KISS_OPTION_PASSALL ? 1 : 0);
+        break;
+
     case hardware::SET_USB_POWER_OFF:
         DEBUG("SET_USB_POWER_OFF");
         if (*it) {
@@ -491,8 +493,6 @@ void Hardware::handle_request(hdlc::IoFrame* frame) {
         reply16(hardware::GET_API_VERSION, hardware::KISS_API_VERSION);
         osMessagePut(audioInputQueueHandle, audio::POLL_BATTERY_LEVEL,
             osWaitForever);
-        osMessagePut(audioInputQueueHandle, audio::POLL_TWIST_LEVEL,
-            osWaitForever);
         osMessagePut(audioInputQueueHandle, audio::IDLE,
             osWaitForever);
         reply(hardware::GET_FIRMWARE_VERSION, (uint8_t*) FIRMWARE_VERSION,
@@ -514,6 +514,7 @@ void Hardware::handle_request(hdlc::IoFrame* frame) {
         reply8(hardware::GET_DUPLEX, duplex);
         reply8(hardware::GET_PTT_CHANNEL,
             options & KISS_OPTION_PTT_SIMPLEX ? 0 : 1);
+        reply8(hardware::GET_PASSALL, options & KISS_OPTION_PASSALL ? 1 : 0);
         reply16(hardware::GET_CAPABILITIES,
             hardware::CAP_EEPROM_SAVE|hardware::CAP_BATTERY_LEVEL|
             hardware::CAP_ADJUST_INPUT|hardware::CAP_DFU_FIRMWARE);
@@ -523,43 +524,60 @@ void Hardware::handle_request(hdlc::IoFrame* frame) {
         reply8(hardware::GET_MAX_INPUT_TWIST, 9);   // Constants for this FW
         reply(hardware::GET_MAC_ADDRESS, mac_address, sizeof(mac_address));
         reply(hardware::GET_DATETIME, get_rtc_datetime(), 7);
+        ext_reply(hardware::EXT_GET_MODEM_TYPE, modem_type);
+        ext_reply(hardware::EXT_GET_MODEM_TYPES, supported_modem_types);
         if (*error_message) {
             reply(hardware::GET_ERROR_MSG, (uint8_t*) error_message, sizeof(error_message));
         }
         break;
 
-    case hardware::EXTENDED_CMD:
-        handle_ext_request(frame);
-        break;
-
     default:
-        ERROR("Unknown hardware request");
+        if (command > 0xC0)
+        {
+            handle_ext_request(frame);
+        }
+        else
+        {
+            ERROR("Unknown hardware request");
+        }
     }
 }
 
-inline void ext_reply(uint8_t cmd, uint8_t result) {
-    uint8_t data[3] { hardware::EXTENDED_CMD, cmd, result };
-    ioport->write(data, 3, 6);
-}
-
 void Hardware::handle_ext_request(hdlc::IoFrame* frame) {
     auto it = frame->begin();
     ++it;
+    // Currently only supports 2-byte extended commands.
     uint8_t ext_command = *it++;
 
     switch (ext_command) {
-    case hardware::EXT_GET_MODEM_TYPE:
+
+    case hardware::EXT_SET_MODEM_TYPE[1]:
+        DEBUG("SET_MODEM_TYPE");
+        if ((*it == hardware::MODEM_TYPE_1200)
+            or (*it == hardware::MODEM_TYPE_9600))
+        {
+            modem_type = *it;
+            DEBUG(modem_type_lookup[modem_type]);
+            update_crc();
+        }
+        else
+        {
+            ERROR("Unsupported modem type");
+        }
+        osMessagePut(audioInputQueueHandle, audio::UPDATE_SETTINGS,
+            osWaitForever);
+        updateModulator();
+        [[fallthrough]];
+    case hardware::EXT_GET_MODEM_TYPE[1]:
         DEBUG("EXT_GET_MODEM_TYPE");
-        ext_reply(hardware::EXT_GET_MODEM_TYPE, 1);
+        ext_reply(hardware::EXT_GET_MODEM_TYPE, modem_type);
         break;
-    case hardware::EXT_SET_MODEM_TYPE:
-        DEBUG("EXT_SET_MODEM_TYPE");
-        ext_reply(hardware::EXT_OK, hardware::EXT_SET_MODEM_TYPE);
-        break;
-    case hardware::EXT_GET_MODEM_TYPES:
+    case hardware::EXT_GET_MODEM_TYPES[1]:
         DEBUG("EXT_GET_MODEM_TYPES");
-        ext_reply(hardware::EXT_GET_MODEM_TYPES, 1);
+        ext_reply(hardware::EXT_GET_MODEM_TYPES, supported_modem_types);
         break;
+    default:
+        ERROR("Unknown extended hardware request");
     }
 }
 
diff --git a/TNC/KissHardware.hpp b/TNC/KissHardware.hpp
index 7881a15..1dc3bbb 100644
--- a/TNC/KissHardware.hpp
+++ b/TNC/KissHardware.hpp
@@ -1,8 +1,7 @@
-// Copyright 2015 Mobilinkd LLC <rob@mobilinkd.com>
+// Copyright 2015-2020 Mobilinkd LLC <rob@mobilinkd.com>
 // All rights reserved.
 
-#ifndef MOBILINKD__TNC__KISS_HARDWARE_HPP_
-#define MOBILINKD__TNC__KISS_HARDWARE_HPP_
+#pragma once
 
 #include "KissHardware.h"
 #include "Log.h"
@@ -35,7 +34,7 @@ namespace hardware {
  * The major version should be updated whenever non-backwards compatible
  * changes to the API are made.
  */
-constexpr const uint16_t KISS_API_VERSION = 0x0200;
+constexpr const uint16_t KISS_API_VERSION = 0x0201;
 
 constexpr const uint16_t CAP_DCD = 0x0100;
 constexpr const uint16_t CAP_SQUELCH = 0x0200;
@@ -94,9 +93,6 @@ constexpr const uint8_t GET_TIMESLOT = 35;
 constexpr const uint8_t GET_TXTAIL = 36;
 constexpr const uint8_t GET_DUPLEX = 37;
 
-constexpr const uint8_t SET_MODEM_TYPE = 38;
-constexpr const uint8_t GET_MODEM_TYPE = 39;
-
 constexpr const uint8_t GET_FIRMWARE_VERSION = 40;
 constexpr const uint8_t GET_HARDWARE_VERSION = 41;
 constexpr const uint8_t SAVE_EEPROM_SETTINGS = 42;
@@ -129,6 +125,9 @@ constexpr const uint8_t GET_BT_POWER_OFF = 78;
 constexpr const uint8_t SET_PTT_CHANNEL = 79; // Which PTT line to use (currently 0 or 1,
 constexpr const uint8_t GET_PTT_CHANNEL = 80; // multiplex or simplex)
 
+constexpr const uint8_t SET_PASSALL = 81;   // Allow invalid CRC through when
+constexpr const uint8_t GET_PASSALL = 82;   // true (1).
+
 constexpr const uint8_t GET_MIN_OUTPUT_TWIST = 119;  ///< int8_t (may be negative).
 constexpr const uint8_t GET_MAX_OUTPUT_TWIST = 120;  ///< int8_t (may be negative).
 constexpr const uint8_t GET_MIN_INPUT_TWIST = 121;  ///< int8_t (may be negative).
@@ -140,34 +139,47 @@ constexpr const uint8_t GET_CAPABILITIES = 126;   ///< Send all capabilities.
 constexpr const uint8_t GET_ALL_VALUES = 127;     ///< Send all settings & versions.
 
 /**
- * Extended commands are two+ bytes in length.  They start at 80:00
- * and go through BF:FF (14 significant bits), then proceed to C0:00:00
- * through CF:FF:FF (20 more significant bits).
+ * Extended commands are two+ bytes in length.  They follow the model used
+ * by UTF-8 to extend the command set.  Extended commands start at C1:80
+ * and go through DF:BF (11 significant bits), then proceed to E0:80:80
+ * through EF:BF:BF (16 significant bits).
  *
- * If needed, the commands can be extended to 9 nibbles (D0 - DF),
- * 13 nibbles (E0-EF) and 17 nibbles (F0-FF).
+ * To avoid special KISS characters, we skip the following byte values in
+ * the first byte:
+ *
+ * - 0xC0 / FEND
+ * - 0xDB / FESC
+ * - 0xDC / TFEND
+ * - 0xDD / TFESC
  */
-constexpr const uint8_t EXTENDED_CMD = 128;
+constexpr const uint8_t EXTENDED_CMD = 0xC1;
 
-constexpr const uint8_t EXT_OK = 0;
-constexpr const uint8_t EXT_GET_MODEM_TYPE = 1;
-constexpr const uint8_t EXT_SET_MODEM_TYPE = 2;
-constexpr const uint8_t EXT_GET_MODEM_TYPES = 3;  ///< Return a list of supported modem types
+constexpr const uint8_t EXT_OK = 0x80;
 
-constexpr const uint8_t EXT_GET_ALIASES = 8;    ///< Number of aliases supported
-constexpr const uint8_t EXT_GET_ALIAS = 9;      ///< Alias number (uint8_t), 8 characters, 5 bytes (set, use, insert_id, preempt, hops)
-constexpr const uint8_t EXT_SET_ALIAS = 10;     ///< Alias number (uint8_t), 8 characters, 5 bytes (set, use, insert_id, preempt, hops)
+constexpr std::array<uint8_t, 2> EXT_GET_MODEM_TYPE = {0xC1, 0x81};
+constexpr std::array<uint8_t, 2> EXT_SET_MODEM_TYPE = {0xC1, 0x82};
+constexpr std::array<uint8_t, 2> EXT_GET_MODEM_TYPES = {0xC1, 0x83};    ///< Return a list of supported modem types
 
-constexpr const uint8_t EXT_GET_BEACONS = 12;   ///< Number of beacons supported
-constexpr const uint8_t EXT_GET_BEACON = 13;    ///< Beacon number (uint8_t), uint16_t interval in seconds, 3 NUL terminated strings (callsign, path, text)
-constexpr const uint8_t EXT_SET_BEACON = 14;    ///< Beacon number (uint8_t), uint16_t interval in seconds, 3 NUL terminated strings (callsign, path, text)
+constexpr std::array<uint8_t, 2> EXT_GET_ALIASES = {0xC1, 0x88};        ///< Number of aliases supported
+constexpr std::array<uint8_t, 2> EXT_GET_ALIAS = {0xC1, 0x89};          ///< Alias number (uint8_t), 8 characters, 5 bytes (set, use, insert_id, preempt, hops)
+constexpr std::array<uint8_t, 2> EXT_SET_ALIAS = {0xC1, 0x0A};          ///< Alias number (uint8_t), 8 characters, 5 bytes (set, use, insert_id, preempt, hops)
 
-constexpr const uint8_t MODEM_TYPE_1200 = 1;
-constexpr const uint8_t MODEM_TYPE_300 = 2;
-constexpr const uint8_t MODEM_TYPE_9600 = 3;
-constexpr const uint8_t MODEM_TYPE_PSK31 = 4;
-constexpr const uint8_t MODEM_TYPE_OFDM = 5;
-constexpr const uint8_t MODEM_TYPE_MFSK16 = 6;
+constexpr std::array<uint8_t, 2> EXT_GET_BEACON_SLOTS = {0xC1, 0x8C};   ///< Number of beacons supported
+constexpr std::array<uint8_t, 2> EXT_GET_BEACON = {0xC1, 0x8D};         ///< Beacon number (uint8_t), uint16_t interval in seconds, 3 NUL terminated strings (callsign, path, text)
+constexpr std::array<uint8_t, 2> EXT_SET_BEACON = {0xC1, 0x8E};         ///< Beacon number (uint8_t), uint16_t interval in seconds, 3 NUL terminated strings (callsign, path, text)
+
+
+/*
+ * Modem type values 0x00 - 0x7F are single-byte types.  Modem type values
+ * starting at 0xC0 are multi-byte values, and should follow the model used
+ * by UTF-8 to extend the modem types, should that ever be necessary.
+ */
+constexpr uint8_t MODEM_TYPE_1200 = 1;
+constexpr uint8_t MODEM_TYPE_300 = 2;
+constexpr uint8_t MODEM_TYPE_9600 = 3;
+constexpr uint8_t MODEM_TYPE_PSK31 = 4;
+constexpr uint8_t MODEM_TYPE_OFDM = 5;
+constexpr uint8_t MODEM_TYPE_MFSK16 = 6;
 
 // Boolean options.
 #define KISS_OPTION_CONN_TRACK      0x01
@@ -175,6 +187,7 @@ constexpr const uint8_t MODEM_TYPE_MFSK16 = 6;
 #define KISS_OPTION_VIN_POWER_ON    0x04  // Power on when plugged into USB
 #define KISS_OPTION_VIN_POWER_OFF   0x08  // Power off when unplugged from USB
 #define KISS_OPTION_PTT_SIMPLEX     0x10  // Simplex PTT (the default)
+#define KISS_OPTION_PASSALL         0x20  // Ignore invalid CRC.
 
 const char TOCALL[] = "APML30"; // Update for every feature change.
 
@@ -210,11 +223,24 @@ const size_t NUMBER_OF_BEACONS = 4;     // 680 bytes
  */
 struct Hardware
 {
+    static constexpr std::array<const char*, 4> modem_type_lookup = {
+        "NOT SET",
+        "AFSK1200",
+        "AFSK300",
+        "FSK9600",
+    };
+
+    // This must match the constants defined above.
     enum ModemType {
-        AFSK1200 = 1,
-        AFSK300,
-        FSK9600,
-        PSK31
+        AFSK1200 = hardware::MODEM_TYPE_1200,
+        AFSK300 = hardware::MODEM_TYPE_300,
+        FSK9600 = hardware::MODEM_TYPE_9600,
+        PSK31 = hardware::MODEM_TYPE_PSK31
+    };
+
+    static constexpr std::array<uint8_t, 2> supported_modem_types = {
+        hardware::MODEM_TYPE_1200,
+        hardware::MODEM_TYPE_9600
     };
 
     uint8_t txdelay;        ///< How long in 10mS units to wait for TX to settle before starting data
@@ -272,7 +298,7 @@ struct Hardware
       slot = 10;
       txtail = 1;
       duplex = 0;
-      modem_type = ModemType::FSK9600;
+      modem_type = ModemType::AFSK1200;
       output_gain = 63;
       input_gain = 0;   // 0-4 on TNC3
       tx_twist = 50;
@@ -299,13 +325,13 @@ struct Hardware
         DEBUG("Slot Time: %d", (int)slot);
         DEBUG("TX Tail: %d", (int)txtail);
         DEBUG("Duplex: %d", (int)duplex);
-        DEBUG("Modem Type: %d", (int)modem_type);
+        DEBUG("Modem Type: %s", modem_type_lookup[modem_type]);
         DEBUG("TX Gain: %d", (int)output_gain);
         DEBUG("RX Gain: %d", (int)input_gain);
         DEBUG("TX Twist: %d", (int)tx_twist);
         DEBUG("RX Twist: %d", (int)rx_twist);
         DEBUG("Log Level: %d", (int)log_level);
-        DEBUG("Options: %d", (int)options);
+        DEBUG("Options: %04hx", options);
         DEBUG("MYCALL: %s", (char*) mycall);
         DEBUG("Dedupe time (secs): %d", (int)dedupe_seconds);
         DEBUG("Aliases:");
@@ -325,7 +351,7 @@ struct Hardware
             DEBUG(" text: %s", (char*)b.text);
             DEBUG(" frequency (secs): %d", (int)b.seconds);
         }
-        DEBUG("Checksum: %04x", checksum);
+        DEBUG("Checksum: %04hx", checksum);
     }
 
     bool load();
@@ -350,7 +376,6 @@ struct Hardware
 
 extern Hardware& settings();
 
-
 struct I2C_Storage
 {
     constexpr static const uint16_t i2c_address{EEPROM_ADDRESS};
@@ -378,5 +403,3 @@ void reply8(uint8_t cmd, uint8_t result) __attribute__((noinline));
 void reply16(uint8_t cmd, uint16_t result) __attribute__((noinline));
 
 }}} // mobilinkd::tnc::kiss
-
-#endif // INMOBILINKD__TNC__KISS_HARDWARE_HPP_C_KISSHARDWARE_HPP_
diff --git a/TNC/Modulator.hpp b/TNC/Modulator.hpp
index 9d3982c..417e4f8 100644
--- a/TNC/Modulator.hpp
+++ b/TNC/Modulator.hpp
@@ -6,6 +6,7 @@
 #include "PTT.hpp"
 #include "KissHardware.hpp"
 
+#include "stm32l4xx_hal.h"
 #include "cmsis_os.h"
 
 #include <cstdint>
@@ -88,6 +89,44 @@ struct Modulator
     virtual void abort() = 0;
 
     virtual float bits_per_ms() const = 0;
+
+protected:
+
+    /**
+     * Stop the DMA conversion and the timer.  Configure DAC for no
+     * trigger and set the DAC level to exactly mid-level.
+     *
+     * @note The DAC is set to mid-level to ensure the audio coupling
+     *  capacitor is kept biased to ensure that there is no DC level
+     *  ramp when we start conversions.  This is bad for FSK.
+     */
+    void stop_conversion()
+    {
+        HAL_DAC_Stop_DMA(&hdac1, DAC_CHANNEL_1);
+        HAL_TIM_Base_Stop(&htim7);
+
+        DAC_ChannelConfTypeDef sConfig;
+
+        sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
+        sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
+        sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
+        sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
+        sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
+        if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)
+        {
+          CxxErrorHandler();
+        }
+
+        if (HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_1, DAC_ALIGN_12B_R, 2048) != HAL_OK)
+        {
+            CxxErrorHandler();
+        }
+        if (HAL_DAC_Start(&hdac1, DAC_CHANNEL_1) != HAL_OK)
+        {
+            CxxErrorHandler();
+        }
+    }
+
 };
 
 }} // mobilinkd::tnc
diff --git a/TNC/ModulatorTask.cpp b/TNC/ModulatorTask.cpp
index 73d7136..6705a5e 100644
--- a/TNC/ModulatorTask.cpp
+++ b/TNC/ModulatorTask.cpp
@@ -2,6 +2,8 @@
 // All rights reserved.
 
 #include "ModulatorTask.hpp"
+#include "HDLCEncoder.hpp"
+#include "Modulator.hpp"
 #include "Fsk9600Modulator.hpp"
 #include "AFSKModulator.hpp"
 #include "KissHardware.hpp"
@@ -50,12 +52,12 @@ mobilinkd::tnc::Modulator& getModulator()
     case kiss::Hardware::ModemType::AFSK1200:
         return afsk1200modulator;
     default:
-        _Error_Handler(__FILE__, __LINE__);
+        CxxErrorHandler();
     }
 }
 
 mobilinkd::tnc::hdlc::Encoder& getEncoder() {
-    static mobilinkd::tnc::hdlc::Encoder instance(hdlcOutputQueueHandle, &getModulator());
+    static mobilinkd::tnc::hdlc::Encoder instance(hdlcOutputQueueHandle);
     return instance;
 }
 
@@ -81,6 +83,16 @@ void updatePtt()
         getModulator().set_ptt(&multiplexPtt);
 }
 
+void updateModulator()
+{
+    using namespace mobilinkd::tnc::kiss;
+
+    modulator = &getModulator();
+    modulator->init(settings());
+    updatePtt();
+    encoder->updateModulator();
+}
+
 void startModulatorTask(void const*) {
 
     using namespace mobilinkd::tnc::kiss;
diff --git a/TNC/ModulatorTask.hpp b/TNC/ModulatorTask.hpp
index b52c98c..903602c 100644
--- a/TNC/ModulatorTask.hpp
+++ b/TNC/ModulatorTask.hpp
@@ -1,12 +1,8 @@
-// Copyright 2015 Mobilinkd LLC <rob@mobilinkd.com>
+// Copyright 2015-2020 Mobilinkd LLC <rob@mobilinkd.com>
 // All rights reserved.
 
+#pragma once
 
-#ifndef MOBILINKD__MODULATOR_TASK_HPP_
-#define MOBILINKD__MODULATOR_TASK_HPP_
-
-#include "HDLCEncoder.hpp"
-#include "Modulator.hpp"
 #include "PTT.hpp"
 #include "cmsis_os.h"
 
@@ -14,10 +10,21 @@
 extern "C" {
 #endif
 
+namespace mobilinkd { namespace tnc {
+
+class Modulator;
+
+namespace hdlc {
+class Encoder;
+}
+
+}}
+
 extern mobilinkd::tnc::SimplexPTT simplexPtt;
 extern mobilinkd::tnc::MultiplexPTT multiplexPtt;
 
 mobilinkd::tnc::Modulator& getModulator();
+mobilinkd::tnc::hdlc::Encoder& getEncoder();
 
 void startModulatorTask(void const * argument);
 
@@ -26,9 +33,8 @@ enum class PTT {SIMPLEX, MULTIPLEX};
 void setPtt(PTT ptt);
 
 void updatePtt(void);
+void updateModulator(void);
 
 #ifdef __cplusplus
 }
 #endif
-
-#endif // MOBILINKD__MODULATOR_TASK_HPP_

From 1a18b3dd1bab452f7b708e5fbe3cab1a3c37ce5d Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sat, 22 Feb 2020 19:37:59 -0600
Subject: [PATCH 08/36] Fix defect in serial port rate limit.

---
 TNC/SerialPort.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/TNC/SerialPort.cpp b/TNC/SerialPort.cpp
index a2ce989..36685bd 100644
--- a/TNC/SerialPort.cpp
+++ b/TNC/SerialPort.cpp
@@ -81,7 +81,6 @@ extern "C" void startSerialTask(void const* arg)
         }
 
         uint8_t c = evt.value.v;
-        INFO("%02x - %c", c, c);
         switch (state) {
         case WAIT_FBEGIN:
             if (c == FEND) state = WAIT_FRAME_TYPE;
@@ -107,6 +106,7 @@ extern "C" void startSerialTask(void const* arg)
                     uint32_t delay = (last_sent_time + 50) - current_sent_time;
                     osDelay(delay);
                 }
+                last_sent_time = current_sent_time;
                 frame = hdlc::acquire_wait();
                 state = WAIT_FBEGIN;
                 break;
@@ -132,7 +132,7 @@ extern "C" void startSerialTask(void const* arg)
                 if (not frame->push_back(FEND)) {
                     hdlc::release(frame);
                     state = WAIT_FBEGIN;  // Drop frame;
-                    frame = hdlc::acquire();
+                    frame = hdlc::acquire_wait();
                 }
                 break;
             default:

From f72a9a3ff6d8795b77b43bfee63ce958be3a6b9c Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sat, 22 Feb 2020 21:35:32 -0600
Subject: [PATCH 09/36] Update passall rules in HDLC decoder to align more
 closely with AX.25 specs.

---
 TNC/HdlcDecoder.cpp | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/TNC/HdlcDecoder.cpp b/TNC/HdlcDecoder.cpp
index bce1f31..44da02e 100644
--- a/TNC/HdlcDecoder.cpp
+++ b/TNC/HdlcDecoder.cpp
@@ -63,24 +63,31 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
         if (flag) {
             switch (buffer) {
             case 0x7E:
-                if (packet->size() > 0) {
+                if (packet->size() > 2) {
                     // We have started decoding a packet.
                     packet->parse_fcs();
                     report_bits = bits;
-                    if (packet->ok()) {
-                        // CRC is OK, assume a good packet, even if there are
-                        // extraneous bits decoded.
+                    if (packet->size() < 15) {
+                        // 120 (136) bits per AX.25 section 3.9.
+                        // Note we discard the flags.
+                        result_code = STATUS_FRAME_ERROR;
+                    } else if (packet->ok()) {
+                        // Not compliant with AX.25 section 3.9.
+                        // We ignore byte alignment when FCS is OK.
                         result_code = STATUS_OK;
                     } else if (bits == 8) {
                         // Otherwise, if there is a CRC error but we are on
                         // an even byte boundary, flag a CRC error.  This is
                         // used by the "pass all" rule.
+                        // Must be byte-aligned per AX.25 section 3.9.
                         result_code = STATUS_CRC_ERROR;
                     } else {
                         // Extraneous bits mean we have a framing error.
                         // We should not pass this frame up the stack.
                         result_code = STATUS_FRAME_ERROR;
                     }
+                } else {
+                    packet->clear();
                 }
                 state = State::SYNC;
                 flag = 0;
@@ -129,12 +136,20 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
         if (packet->size() > 2)
         {
             packet->parse_fcs();
-            if (packet->ok())
+            if (packet->size() < 15) {
+                // 120 (136) bits per AX.25 section 3.9.
+                // Note we discard the flags.
+                result_code = STATUS_NO_CARRIER;
+            }
+            else if (packet->ok())
             {
+                // Not compliant with AX.25 section 3.9.
+                // We ignore byte alignment when FCS is OK.
                 result_code = STATUS_OK;
             }
             else if (bits == 8)
             {
+                // Must be byte-aligned per AX.25 section 3.9.
                 result_code = STATUS_CRC_ERROR;
             }
             else

From 0151ad00e60d86385fc8fd9bae31805e5bf5aa75 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sat, 22 Feb 2020 21:37:13 -0600
Subject: [PATCH 10/36] Move GET_DATETIME to last sent for GET_ALL_VALUES
 because iOS Config App expects that.  Update firmware version to 2.0.0b2.

---
 TNC/KissHardware.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index b4669d4..445fb1a 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -29,7 +29,7 @@ int powerOffViaUSB(void)
 
 namespace mobilinkd { namespace tnc { namespace kiss {
 
-const char FIRMWARE_VERSION[] = "2.0.0b1";
+const char FIRMWARE_VERSION[] = "2.0.0b2";
 const char HARDWARE_VERSION[] = "Mobilinkd TNC3 2.1.1";
 
 
@@ -490,6 +490,7 @@ void Hardware::handle_request(hdlc::IoFrame* frame) {
 
     case hardware::GET_ALL_VALUES:
         DEBUG("GET_ALL_VALUES");
+        // GET_API_VERSION must always come first.
         reply16(hardware::GET_API_VERSION, hardware::KISS_API_VERSION);
         osMessagePut(audioInputQueueHandle, audio::POLL_BATTERY_LEVEL,
             osWaitForever);
@@ -523,12 +524,13 @@ void Hardware::handle_request(hdlc::IoFrame* frame) {
         reply8(hardware::GET_MIN_INPUT_TWIST, -3);  // Constants for this FW
         reply8(hardware::GET_MAX_INPUT_TWIST, 9);   // Constants for this FW
         reply(hardware::GET_MAC_ADDRESS, mac_address, sizeof(mac_address));
-        reply(hardware::GET_DATETIME, get_rtc_datetime(), 7);
         ext_reply(hardware::EXT_GET_MODEM_TYPE, modem_type);
         ext_reply(hardware::EXT_GET_MODEM_TYPES, supported_modem_types);
         if (*error_message) {
             reply(hardware::GET_ERROR_MSG, (uint8_t*) error_message, sizeof(error_message));
         }
+        // GET_DATETIME must always be last.  iOS config app depends on it.
+        reply(hardware::GET_DATETIME, get_rtc_datetime(), 7);
         break;
 
     default:

From 99ef558766b4afbec665cef9beebb9511fca435f Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sun, 23 Feb 2020 15:49:35 -0600
Subject: [PATCH 11/36] Work around hang when changing demodulators.

---
 Inc/FreeRTOSConfig.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Inc/FreeRTOSConfig.h b/Inc/FreeRTOSConfig.h
index d083621..388a1d8 100644
--- a/Inc/FreeRTOSConfig.h
+++ b/Inc/FreeRTOSConfig.h
@@ -67,7 +67,8 @@
 #define configCHECK_FOR_STACK_OVERFLOW           1
 #define configENABLE_BACKWARD_COMPATIBILITY      0
 #define configUSE_PORT_OPTIMISED_TASK_SELECTION  1
-#define configUSE_TICKLESS_IDLE                  1
+// FIXME: configUSE_TICKLESS_IDLE must be 0 or changing modem type locks up.
+#define configUSE_TICKLESS_IDLE                  0
 
 /* Co-routine definitions. */
 #define configUSE_CO_ROUTINES                    0

From a4384706928df11dfb640e355646206261fe3d8c Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sun, 23 Feb 2020 15:53:06 -0600
Subject: [PATCH 12/36] Clean up error_message handling and clock
 initialization.

---
 Src/main.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/Src/main.c b/Src/main.c
index e0dd06f..02a224e 100644
--- a/Src/main.c
+++ b/Src/main.c
@@ -421,6 +421,10 @@ int main(void)
   /* USER CODE BEGIN SysInit */
 #ifdef KISS_LOGGING
   printf("start\r\n");
+  if (error_message[0] != 0) {
+      printf(error_message);
+      error_message[0] = 0;
+  }
 #endif
 
   // Note that it is important that all GPIO interrupts are disabled until
@@ -1454,7 +1458,7 @@ void SysClock48()
     RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
     RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
 
-    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
+    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
     {
       _Error_Handler(__FILE__, __LINE__);
     }
@@ -1499,15 +1503,11 @@ void SysClock80()
     RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
     RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
 
-    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
+    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
     {
       _Error_Handler(__FILE__, __LINE__);
     }
 
-    /**Configure the Systick interrupt time
-    */
-    HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
-
     RCC_OscInitStruct.OscillatorType = 0;
     RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
     RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
@@ -1630,7 +1630,8 @@ void _Error_Handler(char *file, int line)
 #ifdef KISS_LOGGING
   printf("Error handler called from file %s on line %d\r\n", file, line);
 #endif
-  snprintf(error_message, sizeof(error_message), "Error: %s:%d", file, line);
+  snprintf(error_message, sizeof(error_message), "Error: %s:%d\r\n", file, line);
+  error_message[sizeof(error_message) - 1] = 0;
 
   stop_now = 0;
   go_back_to_sleep = 0;

From be4004e82e54b36c3354a60b825c69a92edd211e Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sun, 23 Feb 2020 15:55:07 -0600
Subject: [PATCH 13/36] Move modulator init functions from header to source
 file.

---
 TNC/AFSKModulator.cpp    | 42 +++++++++++++++++++++++++++++++++++++++
 TNC/AFSKModulator.hpp    | 28 +-------------------------
 TNC/Fsk9600Modulator.cpp | 43 +++++++++++++++++++++++++++++++++++++---
 TNC/Fsk9600Modulator.hpp | 39 +++---------------------------------
 4 files changed, 86 insertions(+), 66 deletions(-)
 create mode 100644 TNC/AFSKModulator.cpp

diff --git a/TNC/AFSKModulator.cpp b/TNC/AFSKModulator.cpp
new file mode 100644
index 0000000..e169216
--- /dev/null
+++ b/TNC/AFSKModulator.cpp
@@ -0,0 +1,42 @@
+// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
+// All rights reserved.
+
+#include "AFSKModulator.hpp"
+
+namespace mobilinkd { namespace tnc {
+
+void AFSKModulator::init(const kiss::Hardware& hw)
+{
+    set_twist(hw.tx_twist);
+
+    if (HAL_RCC_GetHCLKFreq() != 48000000)
+    {
+        ERROR("Clock is not 48MHz");
+        CxxErrorHandler();
+    }
+
+    // Configure 48MHz clock for 26.4ksps.
+    htim7.Init.Period = 1817;
+    if (HAL_TIM_Base_Init(&htim7) != HAL_OK)
+    {
+        ERROR("htim7 init failed");
+        CxxErrorHandler();
+    }
+
+    DAC_ChannelConfTypeDef sConfig;
+
+    sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
+    sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
+    sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
+    sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
+    sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
+    if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)
+    {
+      CxxErrorHandler();
+    }
+
+    if (HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_1, DAC_ALIGN_12B_R, 2048) != HAL_OK) CxxErrorHandler();
+    if (HAL_DAC_Start(&hdac1, DAC_CHANNEL_1) != HAL_OK) CxxErrorHandler();
+}
+
+}} // mobilinkd::tnc
diff --git a/TNC/AFSKModulator.hpp b/TNC/AFSKModulator.hpp
index c3b5480..d772d38 100644
--- a/TNC/AFSKModulator.hpp
+++ b/TNC/AFSKModulator.hpp
@@ -84,33 +84,7 @@ struct AFSKModulator : Modulator
             buffer_[i] = 2048;
     }
 
-   void init(const kiss::Hardware& hw) override
-   {
-       set_twist(hw.tx_twist);
-
-       // Configure 48MHz clock for 26.4ksps.
-       htim7.Init.Period = 1817;
-       if (HAL_TIM_Base_Init(&htim7) != HAL_OK)
-       {
-           ERROR("htim7 init failed");
-           CxxErrorHandler();
-       }
-
-       DAC_ChannelConfTypeDef sConfig;
-
-       sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
-       sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
-       sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
-       sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
-       sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
-       if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)
-       {
-         CxxErrorHandler();
-       }
-
-       if (HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_1, DAC_ALIGN_12B_R, 2048) != HAL_OK) CxxErrorHandler();
-       if (HAL_DAC_Start(&hdac1, DAC_CHANNEL_1) != HAL_OK) CxxErrorHandler();
-   }
+   void init(const kiss::Hardware& hw);
 
    void deinit() override
    {
diff --git a/TNC/Fsk9600Modulator.cpp b/TNC/Fsk9600Modulator.cpp
index c461db6..1f5d4ac 100644
--- a/TNC/Fsk9600Modulator.cpp
+++ b/TNC/Fsk9600Modulator.cpp
@@ -5,12 +5,49 @@
 
 namespace mobilinkd { namespace tnc {
 
-#if 0
-const std::array<int16_t, BIT_LEN> Fsk9600Modulator::cos_table = {
+const Fsk9600Modulator::cos_table_type Fsk9600Modulator::cos_table = {
     2047,  2020,  1937,  1801,  1616,  1387,  1120,   822,   502,   169,
     -169,  -502,  -822, -1120, -1387, -1616, -1801, -1937, -2020, -2048
 };
 
-#endif
+void Fsk9600Modulator::init(const kiss::Hardware& hw)
+{
+    for (auto& x : buffer_) x = 2048;
+
+    (void) hw; // unused
+
+    state = State::STOPPED;
+    level = Level::HIGH;
+
+    if (HAL_RCC_GetHCLKFreq() != 80000000)
+    {
+        ERROR("Clock is not 80MHz");
+        CxxErrorHandler();
+    }
+
+    // Configure 80MHz clock for 192ksps.
+    htim7.Init.Period = 416;
+    if (HAL_TIM_Base_Init(&htim7) != HAL_OK)
+    {
+        ERROR("htim7 init failed");
+        CxxErrorHandler();
+    }
+
+    DAC_ChannelConfTypeDef sConfig;
+
+    sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
+    sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
+    sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
+    sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
+    sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
+    if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)
+    {
+      CxxErrorHandler();
+    }
+
+    if (HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_1, DAC_ALIGN_12B_R, 2048) != HAL_OK) CxxErrorHandler();
+    if (HAL_DAC_Start(&hdac1, DAC_CHANNEL_1) != HAL_OK) CxxErrorHandler();
+}
+
 
 }} // mobilinkd::tnc
diff --git a/TNC/Fsk9600Modulator.hpp b/TNC/Fsk9600Modulator.hpp
index a98ac80..aceeaf9 100644
--- a/TNC/Fsk9600Modulator.hpp
+++ b/TNC/Fsk9600Modulator.hpp
@@ -29,10 +29,8 @@ struct Fsk9600Modulator : Modulator
     static constexpr int8_t BIT_LEN = DAC_BUFFER_LEN / 2;
     static constexpr uint16_t VREF = 4095;
 
-    static constexpr std::array<int16_t, BIT_LEN> cos_table{
-        2047,  2020,  1937,  1801,  1616,  1387,  1120,   822,   502,   169,
-        -169,  -502,  -822, -1120, -1387, -1616, -1801, -1937, -2020, -2048
-    };
+    using cos_table_type = std::array<int16_t, Fsk9600Modulator::BIT_LEN>;
+    static const cos_table_type cos_table;
 
     enum class Level { ZERO, HIGH, LOW };
     enum class State { STOPPED, STARTING, RUNNING, STOPPING };
@@ -51,38 +49,7 @@ struct Fsk9600Modulator : Modulator
 
     ~Fsk9600Modulator() override {}
 
-    void init(const kiss::Hardware& hw) override
-    {
-        for (auto& x : buffer_) x = 2048;
-
-        (void) hw; // unused
-
-        state = State::STOPPED;
-        level = Level::HIGH;
-
-        // Configure 80MHz clock for 192ksps.
-        htim7.Init.Period = 416;
-        if (HAL_TIM_Base_Init(&htim7) != HAL_OK)
-        {
-            ERROR("htim7 init failed");
-            CxxErrorHandler();
-        }
-
-        DAC_ChannelConfTypeDef sConfig;
-
-        sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
-        sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
-        sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
-        sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
-        sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
-        if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)
-        {
-          CxxErrorHandler();
-        }
-
-        if (HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_1, DAC_ALIGN_12B_R, 2048) != HAL_OK) CxxErrorHandler();
-        if (HAL_DAC_Start(&hdac1, DAC_CHANNEL_1) != HAL_OK) CxxErrorHandler();
-    }
+    void init(const kiss::Hardware& hw) override;
 
     void deinit() override
     {

From 32111251f87d1f101dd8e90a5d1d6684f20012a5 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sun, 23 Feb 2020 15:57:04 -0600
Subject: [PATCH 14/36] Fix SET_PASSALL handling.

---
 TNC/KissHardware.cpp | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index 445fb1a..573551e 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -430,13 +430,13 @@ void Hardware::handle_request(hdlc::IoFrame* frame) {
 
     case hardware::SET_PASSALL:
         DEBUG("SET_PASSALL");
-        if (!*it) {
-          options &= ~KISS_OPTION_PASSALL;
-        } else {
+        if (*it) {
           options |= KISS_OPTION_PASSALL;
+        } else {
+          options &= ~KISS_OPTION_PASSALL;
         }
         update_crc();
-        break;
+        [[fallthrough]];
     case hardware::GET_PASSALL:
         DEBUG("GET_PASSALL");
         reply8(hardware::GET_PASSALL, options & KISS_OPTION_PASSALL ? 1 : 0);
@@ -568,7 +568,6 @@ void Hardware::handle_ext_request(hdlc::IoFrame* frame) {
         }
         osMessagePut(audioInputQueueHandle, audio::UPDATE_SETTINGS,
             osWaitForever);
-        updateModulator();
         [[fallthrough]];
     case hardware::EXT_GET_MODEM_TYPE[1]:
         DEBUG("EXT_GET_MODEM_TYPE");

From 5503b329e894d7f51a45fd78d59ca47db28ba770 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sun, 23 Feb 2020 15:58:08 -0600
Subject: [PATCH 15/36] Add passall setter.  Move battery level code to
 demodulators because they own the ADC.

---
 TNC/Afsk1200Demodulator.cpp | 74 +++++++++++++++++++++++++++++++-
 TNC/Afsk1200Demodulator.hpp | 10 +++--
 TNC/AudioInput.cpp          | 85 +++++--------------------------------
 TNC/AudioInput.hpp          |  6 +--
 TNC/Demodulator.cpp         |  3 +-
 TNC/Demodulator.hpp         |  5 ++-
 TNC/Fsk9600Demodulator.cpp  | 73 ++++++++++++++++++++++++++++++-
 TNC/Fsk9600Demodulator.hpp  | 12 +++---
 TNC/HdlcDecoder.hpp         |  4 ++
 9 files changed, 180 insertions(+), 92 deletions(-)

diff --git a/TNC/Afsk1200Demodulator.cpp b/TNC/Afsk1200Demodulator.cpp
index ccbef19..2d4277d 100644
--- a/TNC/Afsk1200Demodulator.cpp
+++ b/TNC/Afsk1200Demodulator.cpp
@@ -4,6 +4,7 @@
 #include "Afsk1200Demodulator.hpp"
 #include "Goertzel.h"
 #include "AudioInput.hpp"
+#include "GPIO.hpp"
 
 namespace mobilinkd { namespace tnc {
 
@@ -85,7 +86,6 @@ hdlc::IoFrame* Afsk1200Demodulator::operator()(const q15_t* samples)
 float Afsk1200Demodulator::readTwist()
 {
     DEBUG("enter Afsk1200Demodulator::readTwist");
-    constexpr uint32_t channel = AUDIO_IN;
 
     float g1200 = 0.0f;
     float g2200 = 0.0f;
@@ -137,6 +137,78 @@ float Afsk1200Demodulator::readTwist()
     return result;
 }
 
+uint32_t Afsk1200Demodulator::readBatteryLevel()
+{
+    DEBUG("enter Afsk1200Demodulator::readBatteryLevel");
+
+    ADC_ChannelConfTypeDef sConfig;
+
+    sConfig.Channel = ADC_CHANNEL_VREFINT;
+    sConfig.Rank = ADC_REGULAR_RANK_1;
+    sConfig.SingleDiff = ADC_SINGLE_ENDED;
+    sConfig.SamplingTime = ADC_SAMPLETIME_92CYCLES_5;
+    sConfig.OffsetNumber = ADC_OFFSET_NONE;
+    sConfig.Offset = 0;
+    if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
+        CxxErrorHandler();
+
+    htim6.Init.Period = 48000;
+    if (HAL_TIM_Base_Init(&htim6) != HAL_OK) CxxErrorHandler();
+
+    if (HAL_TIM_Base_Start(&htim6) != HAL_OK)
+        CxxErrorHandler();
+
+    if (HAL_ADC_Start(&hadc1) != HAL_OK) CxxErrorHandler();
+    if (HAL_ADC_PollForConversion(&hadc1, 3) != HAL_OK) CxxErrorHandler();
+    auto vrefint = HAL_ADC_GetValue(&hadc1);
+    if (HAL_ADC_Stop(&hadc1) != HAL_OK) CxxErrorHandler();
+
+    // Disable battery charging while measuring battery voltage.
+    auto usb_ce = gpio::USB_CE::get();
+    gpio::USB_CE::on();
+
+    gpio::BAT_DIVIDER::off();
+    HAL_Delay(1);
+
+    sConfig.Channel = ADC_CHANNEL_15;
+    if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
+        CxxErrorHandler();
+
+    uint32_t vbat = 0;
+    if (HAL_ADC_Start(&hadc1) != HAL_OK) CxxErrorHandler();
+    for (size_t i = 0; i != 8; ++i)
+    {
+        if (HAL_ADC_PollForConversion(&hadc1, 1) != HAL_OK) CxxErrorHandler();
+        vbat += HAL_ADC_GetValue(&hadc1);
+    }
+
+    vbat /= 8;
+
+    if (HAL_ADC_Stop(&hadc1) != HAL_OK) CxxErrorHandler();
+    if (HAL_TIM_Base_Stop(&htim6) != HAL_OK)
+        CxxErrorHandler();
+
+    gpio::BAT_DIVIDER::on();
+
+    // Restore battery charging state.
+    if (!usb_ce) gpio::USB_CE::off();
+
+    INFO("Vref = %lu", vrefint);
+    INFO("Vbat = %lu (raw)", vbat);
+
+    // Order of operations is important to avoid underflow.
+    vbat *= 6600;
+    vbat /= (vrefint + 1);
+
+    uint32_t vref = (vrefint * 3300) + (VREF / 2) / VREF;
+
+    INFO("Vref = %lumV", vref)
+    INFO("Vbat = %lumV", vbat);
+
+    DEBUG("exit Afsk1200Demodulator::readBatteryLevel");
+    return vbat;
+}
+
 const q15_t Afsk1200Demodulator::bpf_coeffs[FILTER_TAP_NUM] = {
     4,     0,    -5,   -10,   -13,   -12,    -9,    -4,    -2,    -4,   -12,   -26,
   -41,   -52,   -51,   -35,    -3,    39,    83,   117,   131,   118,    83,    36,
diff --git a/TNC/Afsk1200Demodulator.hpp b/TNC/Afsk1200Demodulator.hpp
index 57dd59f..c78dee1 100644
--- a/TNC/Afsk1200Demodulator.hpp
+++ b/TNC/Afsk1200Demodulator.hpp
@@ -109,6 +109,8 @@ struct Afsk1200Demodulator : IDemodulator
 
     float readTwist() override;
 
+    uint32_t readBatteryLevel() override;
+
     bool locked() const override
     {
         return locked_;
@@ -119,11 +121,11 @@ struct Afsk1200Demodulator : IDemodulator
         return ADC_BLOCK_SIZE;
     }
 
-    void passall(bool enable) override
+    void passall(bool enabled) override
     {
-        demod1.hdlc_decoder_.passall = enable;
-        demod2.hdlc_decoder_.passall = enable;
-        demod3.hdlc_decoder_.passall = enable;
+        demod1.hdlc_decoder_.setPassall(enabled);
+        demod2.hdlc_decoder_.setPassall(enabled);
+        demod3.hdlc_decoder_.setPassall(enabled);
     }
 };
 
diff --git a/TNC/AudioInput.cpp b/TNC/AudioInput.cpp
index 042f93a..8c8cb89 100644
--- a/TNC/AudioInput.cpp
+++ b/TNC/AudioInput.cpp
@@ -12,6 +12,7 @@
 #include "PortInterface.hpp"
 #include "Goertzel.h"
 #include "DCD.h"
+#include "ModulatorTask.hpp"
 
 #include "arm_math.h"
 #include "stm32l4xx_hal.h"
@@ -113,6 +114,7 @@ extern "C" void startAudioInputTask(void const*) {
         case UPDATE_SETTINGS:
             DEBUG("UPDATE_SETTINGS");
             setAudioInputLevels();
+            updateModulator();
             break;
         case IDLE:
             DEBUG("IDLE");
@@ -126,9 +128,9 @@ extern "C" void startAudioInputTask(void const*) {
 namespace mobilinkd { namespace tnc { namespace audio {
 
 uint32_t adc_buffer[ADC_BUFFER_SIZE];               // Two samples per element.
-uint32_t adc_block_size = ADC_BUFFER_SIZE;          // Based on demodulator.
-uint32_t dma_transfer_size = adc_block_size * 2;    // Transfer size in bytes.
-uint32_t half_buffer_size = adc_block_size / 2;     // Transfer size in words / 2.
+volatile uint32_t adc_block_size = ADC_BUFFER_SIZE;          // Based on demodulator.
+volatile uint32_t dma_transfer_size = adc_block_size * 2;    // Transfer size in bytes.
+volatile uint32_t half_buffer_size = adc_block_size / 2;     // Transfer size in words / 2.
 adc_pool_type adcPool;
 
 void set_adc_block_size(uint32_t block_size)
@@ -208,7 +210,7 @@ void demodulatorTask() {
 }
 
 
-void streamLevels(uint32_t channel, uint8_t cmd) {
+void streamLevels(uint8_t cmd) {
 
     // Stream out Vpp, Vavg, Vmin, Vmax as four 16-bit values, left justified.
 
@@ -307,7 +309,7 @@ levels_type readLevels(uint32_t)
 
     uint16_t pp = vmax - vmin;
     uint16_t avg = iaccum / BLOCKS;
-    DEBUG("exit readLevels");
+    INFO("exit readLevels");
 
     return levels_type(pp, avg, vmin, vmax);
 }
@@ -352,7 +354,6 @@ float readTwist()
 void pollInputTwist()
 {
     DEBUG("enter pollInputTwist");
-    constexpr uint32_t channel = AUDIO_IN;
 
     float g1200 = 0.0f;
     float g2200 = 0.0f;
@@ -411,7 +412,7 @@ void pollInputTwist()
 
 void streamAmplifiedInputLevels() {
     DEBUG("enter streamAmplifiedInputLevels");
-    streamLevels(AUDIO_IN, kiss::hardware::POLL_INPUT_LEVEL);
+    streamLevels(kiss::hardware::POLL_INPUT_LEVEL);
     DEBUG("exit streamAmplifiedInputLevels");
 }
 
@@ -441,72 +442,9 @@ void pollAmplifiedInputLevel() {
     DEBUG("exit pollAmplifiedInputLevel");
 }
 
-void pollBatteryLevel() {
-    DEBUG("enter pollBatteryLevel");
-
-    ADC_ChannelConfTypeDef sConfig;
-
-    sConfig.Channel = ADC_CHANNEL_VREFINT;
-    sConfig.Rank = ADC_REGULAR_RANK_1;
-    sConfig.SingleDiff = ADC_SINGLE_ENDED;
-    sConfig.SamplingTime = ADC_SAMPLETIME_247CYCLES_5;
-    sConfig.OffsetNumber = ADC_OFFSET_NONE;
-    sConfig.Offset = 0;
-    if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
-        CxxErrorHandler();
-
-    htim6.Init.Period = 48000;
-    if (HAL_TIM_Base_Init(&htim6) != HAL_OK) CxxErrorHandler();
-
-    if (HAL_TIM_Base_Start(&htim6) != HAL_OK)
-        CxxErrorHandler();
-
-    if (HAL_ADC_Start(&hadc1) != HAL_OK) CxxErrorHandler();
-    if (HAL_ADC_PollForConversion(&hadc1, 3) != HAL_OK) CxxErrorHandler();
-    auto vrefint = HAL_ADC_GetValue(&hadc1);
-    if (HAL_ADC_Stop(&hadc1) != HAL_OK) CxxErrorHandler();
-
-    // Disable battery charging while measuring battery voltage.
-    auto usb_ce = gpio::USB_CE::get();
-    gpio::USB_CE::on();
-
-    gpio::BAT_DIVIDER::off();
-    HAL_Delay(1);
-
-    sConfig.Channel = ADC_CHANNEL_15;
-    if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
-        CxxErrorHandler();
-
-    uint32_t vbat = 0;
-    if (HAL_ADC_Start(&hadc1) != HAL_OK) CxxErrorHandler();
-    for (size_t i = 0; i != 8; ++i)
-    {
-        if (HAL_ADC_PollForConversion(&hadc1, 1) != HAL_OK) CxxErrorHandler();
-        vbat += HAL_ADC_GetValue(&hadc1);
-    }
-
-    vbat /= 8;
-
-    if (HAL_ADC_Stop(&hadc1) != HAL_OK) CxxErrorHandler();
-    if (HAL_TIM_Base_Stop(&htim6) != HAL_OK)
-        CxxErrorHandler();
-
-    htim6.Init.Period = 1817;
-    if (HAL_TIM_Base_Init(&htim6) != HAL_OK) CxxErrorHandler();
-
-    HAL_Delay(1);
-
-    gpio::BAT_DIVIDER::on();
-    if (!usb_ce) gpio::USB_CE::off();   // Restore battery charging state.
-
-    INFO("Vref = %lu", vrefint);
-    INFO("Vbat = %lu (raw)", vbat);
-
-    // Order of operations is important to avoid underflow.
-    vbat *= 6600;
-    vbat /= (vref + 1);
-
-    INFO("Vbat = %lumV", vbat);
+void pollBatteryLevel()
+{
+    auto vbat = getDemodulator()->readBatteryLevel();
 
     uint8_t data[3];
     data[0] = kiss::hardware::GET_BATTERY_LEVEL;
@@ -514,7 +452,6 @@ void pollBatteryLevel() {
     data[2] = (vbat & 0xFF);
 
     ioport->write(data, 3, 6, 10);
-    DEBUG("exit pollBatteryLevel");
 }
 
 #if 0
diff --git a/TNC/AudioInput.hpp b/TNC/AudioInput.hpp
index 5ede020..0dcf990 100644
--- a/TNC/AudioInput.hpp
+++ b/TNC/AudioInput.hpp
@@ -87,9 +87,9 @@ enum AdcState {
 
 const size_t ADC_BUFFER_SIZE = 384;
 extern uint32_t adc_buffer[];       // Two int16_t samples per element.
-extern uint32_t adc_block_size;
-extern uint32_t dma_transfer_size;
-extern uint32_t half_buffer_size;
+extern volatile uint32_t adc_block_size;
+extern volatile uint32_t dma_transfer_size;
+extern volatile uint32_t half_buffer_size;
 
 // 1kB
 typedef memory::Pool<8, ADC_BUFFER_SIZE * 2> adc_pool_type;
diff --git a/TNC/Demodulator.cpp b/TNC/Demodulator.cpp
index 4aa2bd7..06311c4 100644
--- a/TNC/Demodulator.cpp
+++ b/TNC/Demodulator.cpp
@@ -23,7 +23,6 @@ void IDemodulator::startADC(uint32_t period, uint32_t block_size)
     audio::set_adc_block_size(block_size);
 
     htim6.Init.Period = period;
-    htim6.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
     if (HAL_TIM_Base_Init(&htim6) != HAL_OK)
     {
         CxxErrorHandler();
@@ -35,7 +34,7 @@ void IDemodulator::startADC(uint32_t period, uint32_t block_size)
     }
 
     if (HAL_ADC_Start_DMA(&hadc1, audio::adc_buffer,
-        block_size * 2) != HAL_OK)
+        audio::dma_transfer_size) != HAL_OK)
     {
         CxxErrorHandler();
     }
diff --git a/TNC/Demodulator.hpp b/TNC/Demodulator.hpp
index a7ab9ec..6a5a926 100644
--- a/TNC/Demodulator.hpp
+++ b/TNC/Demodulator.hpp
@@ -24,6 +24,7 @@ struct IDemodulator
     virtual void stop() = 0;
     virtual hdlc::IoFrame* operator()(const q15_t* samples) = 0;
     virtual float readTwist() = 0;
+    virtual uint32_t readBatteryLevel() = 0;
 
     virtual bool locked() const = 0;
     virtual size_t size() const = 0;
@@ -33,10 +34,10 @@ struct IDemodulator
      * are frames which consist of an even multiple of eight bits and are
      * up to 330 bytes, but which do not have a valid checksum.
      *
-     * @param enable is true when enabled and false when disabled.  The
+     * @param enabled is true when enabled and false when disabled.  The
      *  default state is disabled.
      */
-    virtual void passall(bool enable) = 0;
+    virtual void passall(bool enabled) = 0;
 
     virtual ~IDemodulator() {}
 
diff --git a/TNC/Fsk9600Demodulator.cpp b/TNC/Fsk9600Demodulator.cpp
index 8ec4ecb..e15cd2b 100644
--- a/TNC/Fsk9600Demodulator.cpp
+++ b/TNC/Fsk9600Demodulator.cpp
@@ -4,6 +4,7 @@
 #include "Fsk9600Demodulator.hpp"
 #include "Goertzel.h"
 #include "AudioInput.hpp"
+#include "GPIO.hpp"
 
 namespace mobilinkd { namespace tnc {
 
@@ -45,7 +46,6 @@ hdlc::IoFrame* Fsk9600Demodulator::operator()(const q15_t* samples)
 float Fsk9600Demodulator::readTwist()
 {
     DEBUG("enter Fsk9600Demodulator::readTwist");
-    constexpr uint32_t channel = AUDIO_IN;
 
     float g120 = 0.0f;
     float g4800 = 0.0f;
@@ -97,6 +97,77 @@ float Fsk9600Demodulator::readTwist()
     return result;
 }
 
+uint32_t Fsk9600Demodulator::readBatteryLevel()
+{
+    DEBUG("enter Fsk9600Demodulator::readBatteryLevel");
+
+    ADC_ChannelConfTypeDef sConfig;
+
+    sConfig.Channel = ADC_CHANNEL_VREFINT;
+    sConfig.Rank = ADC_REGULAR_RANK_1;
+    sConfig.SingleDiff = ADC_SINGLE_ENDED;
+    sConfig.SamplingTime = ADC_SAMPLETIME_247CYCLES_5;
+    sConfig.OffsetNumber = ADC_OFFSET_NONE;
+    sConfig.Offset = 0;
+    if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
+        CxxErrorHandler();
+
+    htim6.Init.Period = 48000;
+    if (HAL_TIM_Base_Init(&htim6) != HAL_OK) CxxErrorHandler();
+
+    if (HAL_TIM_Base_Start(&htim6) != HAL_OK)
+        CxxErrorHandler();
+
+    if (HAL_ADC_Start(&hadc1) != HAL_OK) CxxErrorHandler();
+    if (HAL_ADC_PollForConversion(&hadc1, 3) != HAL_OK) CxxErrorHandler();
+    auto vrefint = HAL_ADC_GetValue(&hadc1);
+    if (HAL_ADC_Stop(&hadc1) != HAL_OK) CxxErrorHandler();
+
+    // Disable battery charging while measuring battery voltage.
+    auto usb_ce = gpio::USB_CE::get();
+    gpio::USB_CE::on();
+
+    gpio::BAT_DIVIDER::off();
+    HAL_Delay(1);
+
+    sConfig.Channel = ADC_CHANNEL_15;
+    if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
+        CxxErrorHandler();
+
+    uint32_t vbat = 0;
+    if (HAL_ADC_Start(&hadc1) != HAL_OK) CxxErrorHandler();
+    for (size_t i = 0; i != 8; ++i)
+    {
+        if (HAL_ADC_PollForConversion(&hadc1, 1) != HAL_OK) CxxErrorHandler();
+        vbat += HAL_ADC_GetValue(&hadc1);
+    }
+
+    vbat /= 8;
+
+    if (HAL_ADC_Stop(&hadc1) != HAL_OK) CxxErrorHandler();
+    if (HAL_TIM_Base_Stop(&htim6) != HAL_OK)
+        CxxErrorHandler();
+
+    gpio::BAT_DIVIDER::on();
+
+    // Restore battery charging state.
+    if (!usb_ce) gpio::USB_CE::off();
+
+    INFO("Vref = %lu", vrefint);
+    INFO("Vbat = %lu (raw)", vbat);
+
+    // Order of operations is important to avoid underflow.
+    vbat *= 6600;
+    vbat /= (vrefint + 1);
+
+    uint32_t vref = (vrefint * 3300) + (VREF / 2) / VREF;
+
+    INFO("Vref = %lumV", vref)
+    INFO("Vbat = %lumV", vbat);
+
+    DEBUG("exit Fsk9600Demodulator::readBatteryLevel");
+    return vbat;
+}
 
 const Fsk9600Demodulator::bpf_bank_type Fsk9600Demodulator::bpf_bank = {{
     // -3dB
diff --git a/TNC/Fsk9600Demodulator.hpp b/TNC/Fsk9600Demodulator.hpp
index 880ed51..2283cc6 100644
--- a/TNC/Fsk9600Demodulator.hpp
+++ b/TNC/Fsk9600Demodulator.hpp
@@ -29,9 +29,11 @@ struct Fsk9600Demodulator : IDemodulator
 {
     static constexpr size_t FILTER_TAP_NUM = 132;
     static constexpr uint32_t ADC_BLOCK_SIZE = 384;
-    static constexpr uint32_t SAMPLE_RATE = 192000;
     static_assert(audio::ADC_BUFFER_SIZE >= ADC_BLOCK_SIZE);
 
+    static constexpr uint32_t SAMPLE_RATE = 192000;
+    static constexpr uint16_t VREF = 16383;
+
     using bpf_coeffs_type = std::array<int16_t, FILTER_TAP_NUM>;
     using bpf_bank_type = std::array<bpf_coeffs_type, 13>;
     using audio_filter_t = Q15FirFilter<ADC_BLOCK_SIZE, FILTER_TAP_NUM>;
@@ -80,13 +82,13 @@ struct Fsk9600Demodulator : IDemodulator
     void stop() override
     {
         stopADC();
-//        INFO("Setting 4MHz SysClock.");
-//        SysClock48();
         locked_ = false;
     }
 
     float readTwist() override;
 
+    uint32_t readBatteryLevel() override;
+
     hdlc::IoFrame* operator()(const q15_t* samples) override;
 
     bool locked() const override
@@ -99,9 +101,9 @@ struct Fsk9600Demodulator : IDemodulator
         return ADC_BLOCK_SIZE;
     }
 
-    void passall(bool enable) override
+    void passall(bool enabled) override
     {
-        hdlc_decoder_.passall = enable;
+        hdlc_decoder_.setPassall(enabled);
     }
 };
 
diff --git a/TNC/HdlcDecoder.hpp b/TNC/HdlcDecoder.hpp
index 82ac73e..bece5f2 100644
--- a/TNC/HdlcDecoder.hpp
+++ b/TNC/HdlcDecoder.hpp
@@ -54,6 +54,10 @@ struct NewDecoder
 
     optional_result_type operator()(bool input, bool pll_lock);
     uint8_t process(bool input, bool pll_lock);
+    void setPassall(bool enabled)
+    {
+        passall = enabled;
+    }
 };
 
 }}} // mobilinkd::tnc::hdlc

From 240f7b0413b78c15e38ef3be4761a9c72e5cc980 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sun, 23 Feb 2020 16:32:47 -0600
Subject: [PATCH 16/36] Fix battery level values when 9600 baud is selected.

---
 TNC/Afsk1200Demodulator.cpp | 4 ++--
 TNC/Fsk9600Demodulator.cpp  | 4 ++--
 TNC/Fsk9600Demodulator.hpp  | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/TNC/Afsk1200Demodulator.cpp b/TNC/Afsk1200Demodulator.cpp
index 2d4277d..a277063 100644
--- a/TNC/Afsk1200Demodulator.cpp
+++ b/TNC/Afsk1200Demodulator.cpp
@@ -198,9 +198,9 @@ uint32_t Afsk1200Demodulator::readBatteryLevel()
 
     // Order of operations is important to avoid underflow.
     vbat *= 6600;
-    vbat /= (vrefint + 1);
+    vbat /= (VREF + 1);
 
-    uint32_t vref = (vrefint * 3300) + (VREF / 2) / VREF;
+    uint32_t vref = ((vrefint * 3300) + (VREF / 2)) / VREF;
 
     INFO("Vref = %lumV", vref)
     INFO("Vbat = %lumV", vbat);
diff --git a/TNC/Fsk9600Demodulator.cpp b/TNC/Fsk9600Demodulator.cpp
index e15cd2b..18e198a 100644
--- a/TNC/Fsk9600Demodulator.cpp
+++ b/TNC/Fsk9600Demodulator.cpp
@@ -158,9 +158,9 @@ uint32_t Fsk9600Demodulator::readBatteryLevel()
 
     // Order of operations is important to avoid underflow.
     vbat *= 6600;
-    vbat /= (vrefint + 1);
+    vbat /= (VREF + 1);
 
-    uint32_t vref = (vrefint * 3300) + (VREF / 2) / VREF;
+    uint32_t vref = ((vrefint * 3300) + (VREF / 2)) / VREF;
 
     INFO("Vref = %lumV", vref)
     INFO("Vbat = %lumV", vbat);
diff --git a/TNC/Fsk9600Demodulator.hpp b/TNC/Fsk9600Demodulator.hpp
index 2283cc6..4a57f5d 100644
--- a/TNC/Fsk9600Demodulator.hpp
+++ b/TNC/Fsk9600Demodulator.hpp
@@ -32,7 +32,7 @@ struct Fsk9600Demodulator : IDemodulator
     static_assert(audio::ADC_BUFFER_SIZE >= ADC_BLOCK_SIZE);
 
     static constexpr uint32_t SAMPLE_RATE = 192000;
-    static constexpr uint16_t VREF = 16383;
+    static constexpr uint16_t VREF = 4095;
 
     using bpf_coeffs_type = std::array<int16_t, FILTER_TAP_NUM>;
     using bpf_bank_type = std::array<bpf_coeffs_type, 13>;

From 0aedbc6d0f71b85e874efd11fec80d2c1a3b805d Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sun, 23 Feb 2020 16:33:12 -0600
Subject: [PATCH 17/36] Update firmware version to 2.0.0b3.

---
 TNC/KissHardware.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index 573551e..392c696 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -29,7 +29,7 @@ int powerOffViaUSB(void)
 
 namespace mobilinkd { namespace tnc { namespace kiss {
 
-const char FIRMWARE_VERSION[] = "2.0.0b2";
+const char FIRMWARE_VERSION[] = "2.0.0b3";
 const char HARDWARE_VERSION[] = "Mobilinkd TNC3 2.1.1";
 
 

From d014d8055fe37001b8a6a9d1cc410e5239d08c22 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Mon, 24 Feb 2020 22:36:09 -0600
Subject: [PATCH 18/36] Convert serial RX code to DMA to improve reliability,
 throughput and flow control.

---
 Src/stm32l4xx_it.c |   8 ++
 TNC/HdlcFrame.hpp  |   2 +
 TNC/SerialPort.cpp | 270 ++++++++++++++++++++++++++++++++++-----------
 3 files changed, 214 insertions(+), 66 deletions(-)

diff --git a/Src/stm32l4xx_it.c b/Src/stm32l4xx_it.c
index b8bf14e..6f28f29 100644
--- a/Src/stm32l4xx_it.c
+++ b/Src/stm32l4xx_it.c
@@ -41,6 +41,8 @@
 #include "main.h"
 extern osMessageQId ioEventQueueHandle;
 
+void idleInterruptCallback(UART_HandleTypeDef* huart);
+
 /* USER CODE END 0 */
 
 /* External variables --------------------------------------------------------*/
@@ -386,6 +388,12 @@ void USART3_IRQHandler(void)
 {
   /* USER CODE BEGIN USART3_IRQn 0 */
 
+    if (__HAL_UART_GET_FLAG(&huart3, UART_FLAG_IDLE)) {
+        idleInterruptCallback(&huart3);
+        __HAL_UART_CLEAR_FLAG(&huart3, UART_FLAG_IDLE);
+        return;
+    }
+
   /* USER CODE END USART3_IRQn 0 */
   HAL_UART_IRQHandler(&huart3);
   /* USER CODE BEGIN USART3_IRQn 1 */
diff --git a/TNC/HdlcFrame.hpp b/TNC/HdlcFrame.hpp
index d67be06..7b161fc 100644
--- a/TNC/HdlcFrame.hpp
+++ b/TNC/HdlcFrame.hpp
@@ -162,6 +162,8 @@ public:
 
     uint16_t size() const {return free_list_.size();}
 
+    static constexpr uint16_t capacity() { return SIZE; }
+
     frame_type* acquire() {
         frame_type* result = nullptr;
         auto x = taskENTER_CRITICAL_FROM_ISR();
diff --git a/TNC/SerialPort.cpp b/TNC/SerialPort.cpp
index 36685bd..b3a37d6 100644
--- a/TNC/SerialPort.cpp
+++ b/TNC/SerialPort.cpp
@@ -13,20 +13,28 @@
 #include "cmsis_os.h"
 
 #include <cstdlib>
+#include <cstdint>
 #include <cstring>
 #include <atomic>
 
 extern UART_HandleTypeDef huart3;
 extern osMessageQId ioEventQueueHandle;
 
-uint8_t rxBuffer;
-std::atomic<int> uart_error{HAL_UART_ERROR_NONE};
+std::atomic<uint32_t> uart_error{HAL_UART_ERROR_NONE};
 
 std::atomic<bool> txDoneFlag{true};
 
 uint8_t tmpBuffer[mobilinkd::tnc::TX_BUFFER_SIZE];
 uint8_t tmpBuffer2[mobilinkd::tnc::TX_BUFFER_SIZE];
 
+constexpr const int RX_BUFFER_SIZE = 127;
+unsigned char rxBuffer[RX_BUFFER_SIZE * 2];
+
+// 3 chunks of 128 bytes.  The first byte in each chunk is the length.
+typedef mobilinkd::tnc::memory::Pool<
+    3, RX_BUFFER_SIZE + 1> serial_pool_type;
+serial_pool_type serialPool;
+
 void log_frame(mobilinkd::tnc::hdlc::IoFrame* frame)
 {
     int pos = 0;
@@ -41,7 +49,56 @@ void log_frame(mobilinkd::tnc::hdlc::IoFrame* frame)
     DEBUG((char*)tmpBuffer2);
 }
 
-extern "C" void startSerialTask(void const* arg)
+// HAL does not have
+HAL_StatusTypeDef UART_DMAPauseReceive(UART_HandleTypeDef *huart)
+{
+  /* Process Locked */
+  __HAL_LOCK(huart);
+
+  if ((huart->RxState == HAL_UART_STATE_BUSY_RX) &&
+      (HAL_IS_BIT_SET(huart->Instance->CR3, USART_CR3_DMAR)))
+  {
+    /* Disable PE and ERR (Frame error, noise error, overrun error) interrupts */
+    CLEAR_BIT(huart->Instance->CR1, USART_CR1_PEIE);
+    CLEAR_BIT(huart->Instance->CR3, USART_CR3_EIE);
+
+    /* Disable the UART DMA Rx request */
+    CLEAR_BIT(huart->Instance->CR3, USART_CR3_DMAR);
+  }
+
+  /* Process Unlocked */
+  __HAL_UNLOCK(huart);
+
+  return HAL_OK;
+}
+
+HAL_StatusTypeDef UART_DMAResumeReceive(UART_HandleTypeDef *huart)
+{
+  /* Process Locked */
+  __HAL_LOCK(huart);
+
+  if (huart->RxState == HAL_UART_STATE_BUSY_RX)
+  {
+    /* Clear the Overrun flag before resuming the Rx transfer */
+    __HAL_UART_CLEAR_FLAG(huart, UART_CLEAR_OREF);
+
+    /* Reenable PE and ERR (Frame error, noise error, overrun error) interrupts */
+    SET_BIT(huart->Instance->CR1, USART_CR1_PEIE);
+    SET_BIT(huart->Instance->CR3, USART_CR3_EIE);
+
+    /* Enable the UART DMA Rx request */
+    SET_BIT(huart->Instance->CR3, USART_CR3_DMAR);
+  }
+
+  /* Process Unlocked */
+  __HAL_UNLOCK(huart);
+
+  return HAL_OK;
+}
+
+extern "C" void startSerialTask(void const* arg) __attribute__((optimize("-O1")));
+
+void startSerialTask(void const* arg)
 {
     using namespace mobilinkd::tnc;
 
@@ -58,90 +115,116 @@ extern "C" void startSerialTask(void const* arg)
 
     hdlc::IoFrame* frame = hdlc::acquire_wait();
 
-    HAL_UART_Receive_IT(&huart3, &rxBuffer, 1);
+    HAL_UART_Receive_DMA(&huart3, rxBuffer, RX_BUFFER_SIZE * 2);
+    __HAL_UART_ENABLE_IT(&huart3, UART_IT_IDLE);
 
     uint32_t last_sent_time = osKernelSysTick();
     uint32_t current_sent_time = 0;
+    bool paused = false;
 
     while (true) {
         osEvent evt = osMessageGet(serialPort->queue(), osWaitForever);
 
         if (evt.status != osEventMessage) {
-            HAL_UART_Receive_IT(&huart3, &rxBuffer, 1);
             continue;
         }
 
-        if (evt.value.v & 0x100) {
+        if (evt.value.v < FLASH_BASE) // Assumes FLASH_BASE < SRAM_BASE.
+        {
+            // Error received.
             hdlc::release(frame);
-            ERROR("UART Error: %08lx", evt.value.v);
+            ERROR("UART Error: %08lx", uart_error.load());
             uart_error.store(HAL_UART_ERROR_NONE);
             frame = hdlc::acquire_wait();
-            HAL_UART_Receive_IT(&huart3, &rxBuffer, 1);
+            HAL_UART_Receive_DMA(&huart3, rxBuffer, RX_BUFFER_SIZE * 2);
+            __HAL_UART_ENABLE_IT(&huart3, UART_IT_IDLE);
             continue;
         }
 
-        uint8_t c = evt.value.v;
-        switch (state) {
-        case WAIT_FBEGIN:
-            if (c == FEND) state = WAIT_FRAME_TYPE;
-            break;
-        case WAIT_FRAME_TYPE:
-            if (c == FEND) break;   // Still waiting for FRAME_TYPE.
-            frame->type(c);
-            state = WAIT_FEND;
-            break;
-        case WAIT_FEND:
-            switch (c) {
-            case FESC:
-                state = WAIT_ESCAPED;
+        auto block = (serial_pool_type::chunk_type*) evt.value.p;
+        auto data = static_cast<unsigned char*>(block->buffer);
+
+        uint8_t end = data[0] + 1;
+        for (uint8_t i = 1; i != end; ++i) {
+            uint8_t c = data[i];
+            switch (state) {
+            case WAIT_FBEGIN:
+                if (c == FEND) state = WAIT_FRAME_TYPE;
                 break;
-            case FEND:
-                frame->source(hdlc::IoFrame::SERIAL_DATA);
-                if (osMessagePut(ioEventQueueHandle, reinterpret_cast<uint32_t>(frame), osWaitForever) != osOK)
-                {
-                    hdlc::release(frame);
+            case WAIT_FRAME_TYPE:
+                if (c == FEND) break;   // Still waiting for FRAME_TYPE.
+                if (c < 8 or c == 0xFF) {
+                    frame->type(c);
+                    state = WAIT_FEND;
+                } else {
+                    WARN("Bad frame type");
+                    state = WAIT_FBEGIN;
                 }
-                current_sent_time = osKernelSysTick();
-                if (last_sent_time + 50 > current_sent_time) {
-                    uint32_t delay = (last_sent_time + 50) - current_sent_time;
-                    osDelay(delay);
-                }
-                last_sent_time = current_sent_time;
-                frame = hdlc::acquire_wait();
-                state = WAIT_FBEGIN;
                 break;
-            default:
-                if (not frame->push_back(c)) {
+            case WAIT_FEND:
+                switch (c) {
+                case FESC:
+                    state = WAIT_ESCAPED;
+                    break;
+                case FEND:
+                    frame->source(hdlc::IoFrame::SERIAL_DATA);
+                    if (osMessagePut(
+                        ioEventQueueHandle,
+                        reinterpret_cast<uint32_t>(frame),
+                        osWaitForever) != osOK)
+                    {
+                        WARN("Failed to send serial frame");
+                        hdlc::release(frame);
+                    }
+
+                    if (hdlc::ioFramePool().size() < (hdlc::ioFramePool().capacity() / 4))
+                    {
+                        UART_DMAPauseReceive(&huart3);
+                        WARN("Pausing UART RX");
+                        while (hdlc::ioFramePool().size() < (hdlc::ioFramePool().capacity() / 2))
+                        {
+                            osThreadYield();
+                        }
+                        UART_DMAResumeReceive(&huart3);
+                    }
+
+                    frame = hdlc::acquire_wait();
+                    state = WAIT_FBEGIN;
+                    break;
+                default:
+                    if (not frame->push_back(c)) {
+                        hdlc::release(frame);
+                        state = WAIT_FBEGIN;  // Drop frame;
+                        frame = hdlc::acquire_wait();
+                    }
+                }
+                break;
+            case WAIT_ESCAPED:
+                state = WAIT_FEND;
+                switch (c) {
+                case TFESC:
+                    if (not frame->push_back(FESC)) {
+                        hdlc::release(frame);
+                        state = WAIT_FBEGIN;  // Drop frame;
+                        frame = hdlc::acquire_wait();
+                    }
+                    break;
+                case TFEND:
+                    if (not frame->push_back(FEND)) {
+                        hdlc::release(frame);
+                        state = WAIT_FBEGIN;  // Drop frame;
+                        frame = hdlc::acquire_wait();
+                    }
+                    break;
+                default:
                     hdlc::release(frame);
                     state = WAIT_FBEGIN;  // Drop frame;
                     frame = hdlc::acquire_wait();
                 }
+                break;
             }
-            break;
-        case WAIT_ESCAPED:
-            state = WAIT_FEND;
-            switch (c) {
-            case TFESC:
-                if (not frame->push_back(FESC)) {
-                    hdlc::release(frame);
-                    state = WAIT_FBEGIN;  // Drop frame;
-                    frame = hdlc::acquire_wait();
-                }
-                break;
-            case TFEND:
-                if (not frame->push_back(FEND)) {
-                    hdlc::release(frame);
-                    state = WAIT_FBEGIN;  // Drop frame;
-                    frame = hdlc::acquire_wait();
-                }
-                break;
-            default:
-                hdlc::release(frame);
-                state = WAIT_FBEGIN;  // Drop frame;
-                frame = hdlc::acquire_wait();
-            }
-            break;
         }
+        serialPool.deallocate(block);
     }
 }
 
@@ -151,18 +234,73 @@ extern "C" void HAL_UART_TxCpltCallback(UART_HandleTypeDef*)
     txDoneFlag = true;
 }
 
-extern "C" void HAL_UART_RxCpltCallback(UART_HandleTypeDef *)
+extern "C" void HAL_UART_RxHalfCpltCallback(UART_HandleTypeDef *huart)
 {
-    osMessagePut(mobilinkd::tnc::getSerialPort()->queue(), (uint32_t) rxBuffer, 0);
+    uint32_t len = (RX_BUFFER_SIZE * 2) - __HAL_DMA_GET_COUNTER(huart->hdmarx);
+    if (len == 0) return;
+    if (len > RX_BUFFER_SIZE) {
+        len = RX_BUFFER_SIZE; // wrapped.
+    }
 
-    HAL_UART_Receive_IT(&huart3, &rxBuffer, 1);
+    auto block = serialPool.allocate();
+    if (!block) return;
+    memmove(block->buffer + 1, rxBuffer, len);
+    block->buffer[0] = len;
+    auto status = osMessagePut(mobilinkd::tnc::getSerialPort()->queue(), (uint32_t) block, 0);
+    if (status != osOK) serialPool.deallocate(block);
 }
 
+extern "C" void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
+{
+    uint32_t hdmarx = __HAL_DMA_GET_COUNTER(huart->hdmarx);
+    uint32_t len = 0;
+    if (hdmarx > RX_BUFFER_SIZE) {
+        len = RX_BUFFER_SIZE;   // wrapped.
+    } else {
+        len = RX_BUFFER_SIZE - hdmarx;
+    }
+    if (len == 0) return;
+
+    auto block = serialPool.allocate();
+    if (!block) return;
+    memmove(block->buffer + 1, rxBuffer + RX_BUFFER_SIZE, len);
+    block->buffer[0] = len;
+    auto status = osMessagePut(mobilinkd::tnc::getSerialPort()->queue(), (uint32_t) block, 0);
+    if (status != osOK) serialPool.deallocate(block);
+}
+
+extern "C" void idleInterruptCallback(UART_HandleTypeDef* huart)
+{
+    uint32_t len = (RX_BUFFER_SIZE * 2) - __HAL_DMA_GET_COUNTER(huart->hdmarx);
+
+    if (len == 0) return;
+
+    auto block = serialPool.allocate();
+    if (!block) return;
+
+    HAL_UART_AbortReceive(huart);
+
+    if (len > RX_BUFFER_SIZE) {
+        // Second half
+        len = len - RX_BUFFER_SIZE;
+        memmove(block->buffer + 1, rxBuffer + RX_BUFFER_SIZE, len);
+    } else {
+        // First half
+        memmove(block->buffer + 1, rxBuffer, len);
+    }
+
+    block->buffer[0] = len;
+
+    HAL_UART_Receive_DMA(huart, rxBuffer, RX_BUFFER_SIZE * 2);
+
+    auto status = osMessagePut(mobilinkd::tnc::getSerialPort()->queue(), (uint32_t) block, 0);
+    if (status != osOK) serialPool.deallocate(block);
+
+}
 
 extern "C" void HAL_UART_ErrorCallback(UART_HandleTypeDef* huart)
 {
-    osMessagePut(mobilinkd::tnc::getSerialPort()->queue(),
-        (uint32_t) (huart->gState<<16) | huart->ErrorCode | 0x100, 0);
+    osMessagePut(mobilinkd::tnc::getSerialPort()->queue(), huart->ErrorCode, 0);
     uart_error.store((huart->gState<<16) | huart->ErrorCode);
     huart->ErrorCode = HAL_UART_ERROR_NONE;
     huart->gState = HAL_UART_STATE_READY;

From e538c20e5819961dd4362864240da960bc2e1e05 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Mon, 24 Feb 2020 22:36:52 -0600
Subject: [PATCH 19/36] Ensure frame type is set for RF frames.

---
 TNC/AudioInput.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/TNC/AudioInput.cpp b/TNC/AudioInput.cpp
index 8c8cb89..d956795 100644
--- a/TNC/AudioInput.cpp
+++ b/TNC/AudioInput.cpp
@@ -187,6 +187,7 @@ void demodulatorTask() {
         auto frame = (*demodulator)(normalized);
         if (frame)
         {
+            frame->source(hdlc::IoFrame::RF_DATA);
             if (osMessagePut(ioEventQueueHandle, (uint32_t) frame, 1) != osOK)
             {
                 hdlc::release(frame);

From 6d01c396f7453e23767ff1b6fe6659a487fdfd67 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Mon, 24 Feb 2020 22:37:41 -0600
Subject: [PATCH 20/36] Add default case in frame handling code to catch
 corrupt frame types.

---
 TNC/IOEventTask.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/TNC/IOEventTask.cpp b/TNC/IOEventTask.cpp
index 69fe5a7..597be66 100644
--- a/TNC/IOEventTask.cpp
+++ b/TNC/IOEventTask.cpp
@@ -375,6 +375,10 @@ void startIOEventTask(void const*)
         case IoFrame::FRAME_RETURN:
             hdlc::release(frame);
             break;
+        default:
+            ERROR("Unknown Frame Type");
+            hdlc::release(frame);
+            break;
         }
     }
 }

From 40bc4af9a7e5f91f165ac16dd5d3128ba84ffb80 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Mon, 24 Feb 2020 22:38:20 -0600
Subject: [PATCH 21/36] Explicitly update the modulator when KISS settings are
 updated.

---
 TNC/Kiss.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/TNC/Kiss.cpp b/TNC/Kiss.cpp
index 72c84cc..eb96cd6 100644
--- a/TNC/Kiss.cpp
+++ b/TNC/Kiss.cpp
@@ -4,6 +4,7 @@
 #include <Log.h>
 #include "Kiss.hpp"
 #include "KissHardware.hpp"
+#include "ModulatorTask.hpp"
 
 // extern osMessageQId hdlcOutputQueueHandle;
 
@@ -26,16 +27,19 @@ void handle_frame(uint8_t frame_type, hdlc::IoFrame* frame) {
         DEBUG("FRAME_TX_DELAY");
         kiss::settings().txdelay = value;
         hdlc::release(frame);
+        updateModulator();
         break;
     case kiss::FRAME_P_PERSIST:
         DEBUG("FRAME_P_PERSIST");
         kiss::settings().ppersist = value;
         hdlc::release(frame);
+        updateModulator();
         break;
     case kiss::FRAME_SLOT_TIME:
         DEBUG("FRAME_SLOT_TIME");
         kiss::settings().slot = value;
         hdlc::release(frame);
+        updateModulator();
         break;
     case kiss::FRAME_TX_TAIL:
         DEBUG("FRAME_TX_TAIL");
@@ -46,6 +50,7 @@ void handle_frame(uint8_t frame_type, hdlc::IoFrame* frame) {
         DEBUG("FRAME_DUPLEX");
         kiss::settings().duplex = value;
         hdlc::release(frame);
+        updateModulator();
         break;
     case kiss::FRAME_HARDWARE:
         DEBUG("FRAME_HARDWARE");

From 6cc5d91a2774fe1e22de9f033f01d8f78410b470 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Mon, 24 Feb 2020 22:38:49 -0600
Subject: [PATCH 22/36] Update Exclipse project settings.

---
 .cproject                       | 16 ++++++++--------
 .settings/language.settings.xml |  4 ++--
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/.cproject b/.cproject
index a57d2b0..1627e0b 100644
--- a/.cproject
+++ b/.cproject
@@ -27,7 +27,7 @@
 							<option id="ilg.gnuarmeclipse.managedbuild.cross.option.debugging.format.1959890047" name="Debug format" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.debugging.format" useByScannerDiscovery="true"/>
 							<option id="ilg.gnuarmeclipse.managedbuild.cross.option.toolchain.name.606808162" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.toolchain.name" useByScannerDiscovery="false" value="GNU Tools for ARM Embedded Processors" valueType="string"/>
 							<option id="ilg.gnuarmeclipse.managedbuild.cross.option.architecture.355585421" name="Architecture" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.architecture" useByScannerDiscovery="false" value="ilg.gnuarmeclipse.managedbuild.cross.option.architecture.arm" valueType="enumerated"/>
-							<option id="ilg.gnuarmeclipse.managedbuild.cross.option.arm.target.family.1992692312" name="ARM family" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.arm.target.family" useByScannerDiscovery="false" value="ilg.gnuarmeclipse.managedbuild.cross.option.arm.target.mcpu.cortex-m4" valueType="enumerated"/>
+							<option id="ilg.gnuarmeclipse.managedbuild.cross.option.arm.target.family.1992692312" name="ARM family (-mcpu)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.arm.target.family" useByScannerDiscovery="false" value="ilg.gnuarmeclipse.managedbuild.cross.option.arm.target.mcpu.cortex-m4" valueType="enumerated"/>
 							<option id="ilg.gnuarmeclipse.managedbuild.cross.option.arm.target.instructionset.203230960" name="Instruction set" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.arm.target.instructionset" useByScannerDiscovery="false" value="ilg.gnuarmeclipse.managedbuild.cross.option.arm.target.instructionset.thumb" valueType="enumerated"/>
 							<option id="ilg.gnuarmeclipse.managedbuild.cross.option.command.prefix.2009350133" name="Prefix" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.command.prefix" useByScannerDiscovery="false" value="arm-none-eabi-" valueType="string"/>
 							<option id="ilg.gnuarmeclipse.managedbuild.cross.option.command.c.529320578" name="C compiler" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.command.c" useByScannerDiscovery="false" value="gcc" valueType="string"/>
@@ -56,7 +56,7 @@
 							<builder autoBuildTarget="all" buildPath="${workspace_loc:/TNC3-firmware}/ARM Debug" cleanBuildTarget="clean" command="${cross_make}" enableAutoBuild="true" id="org.eclipse.cdt.build.core.internal.builder.1584568207" incrementalBuildTarget="all" keepEnvironmentInBuildfile="false" managedBuildOn="true" name="CDT Internal Builder" parallelBuildOn="false" superClass="org.eclipse.cdt.build.core.internal.builder"/>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler.1401064567" name="GNU ARM Cross Assembler" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler">
 								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.usepreprocessor.33292167" name="Use preprocessor" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.usepreprocessor" useByScannerDiscovery="false" value="true" valueType="boolean"/>
-								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths.685185658" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths" useByScannerDiscovery="true" valueType="includePath">
+								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths.685185658" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.include.paths" useByScannerDiscovery="true" valueType="includePath">
 									<listOptionValue builtIn="false" value="/usr/arm-none-eabi/include"/>
 									<listOptionValue builtIn="false" value="../Inc"/>
 									<listOptionValue builtIn="false" value="../Drivers/STM32L4xx_HAL_Driver/Inc"/>
@@ -69,7 +69,7 @@
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Inc/"/>
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Core/Inc"/>
 								</option>
-								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs.2108011045" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
+								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs.2108011045" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.assembler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
 									<listOptionValue builtIn="false" value="__FPU_PRESENT=1"/>
 									<listOptionValue builtIn="false" value="USE_HAL_DRIVER"/>
 									<listOptionValue builtIn="false" value="ARM_MATH_CM4"/>
@@ -80,7 +80,7 @@
 								<inputType id="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler.input.820649784" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.assembler.input"/>
 							</tool>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler.1175769653" name="GNU ARM Cross C Compiler" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler">
-								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths.377832116" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
+								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths.377832116" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
 									<listOptionValue builtIn="false" value="/usr/arm-none-eabi/include"/>
 									<listOptionValue builtIn="false" value="../Inc"/>
 									<listOptionValue builtIn="false" value="../Drivers/CMSIS/Include"/>
@@ -93,7 +93,7 @@
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Core/Inc"/>
 									<listOptionValue builtIn="false" value="../Drivers/STM32L4xx_HAL_Driver/Inc"/>
 								</option>
-								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs.2123477218" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
+								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs.2123477218" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.c.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
 									<listOptionValue builtIn="false" value="__FPU_PRESENT=1"/>
 									<listOptionValue builtIn="false" value="USE_HAL_DRIVER"/>
 									<listOptionValue builtIn="false" value="ARM_MATH_CM4"/>
@@ -107,7 +107,7 @@
 								<inputType id="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler.input.1359599970" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.c.compiler.input"/>
 							</tool>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.compiler.1728068044" name="GNU ARM Cross C++ Compiler" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.compiler">
-								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths.1069495617" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
+								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths.1069495617" name="Include paths (-I)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.include.paths" useByScannerDiscovery="true" valueType="includePath">
 									<listOptionValue builtIn="false" value="/usr/arm-none-eabi/include"/>
 									<listOptionValue builtIn="false" value="../Inc"/>
 									<listOptionValue builtIn="false" value="../Drivers/STM32L4xx_HAL_Driver/Inc"/>
@@ -121,7 +121,7 @@
 									<listOptionValue builtIn="false" value="../Middlewares/ST/STM32_USB_Device_Library/Core/Inc"/>
 									<listOptionValue builtIn="false" value="/usr/local/include"/>
 								</option>
-								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs.1120661678" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
+								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs.1120661678" name="Defined symbols (-D)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.compiler.defs" useByScannerDiscovery="true" valueType="definedSymbols">
 									<listOptionValue builtIn="false" value="__FPU_PRESENT=1"/>
 									<listOptionValue builtIn="false" value="USE_HAL_DRIVER"/>
 									<listOptionValue builtIn="false" value="ARM_MATH_CM4"/>
@@ -148,7 +148,7 @@
 							</tool>
 							<tool id="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.linker.1645159175" name="GNU ARM Cross C++ Linker" superClass="ilg.gnuarmeclipse.managedbuild.cross.tool.cpp.linker">
 								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.gcsections.1081471382" name="Remove unused sections (-Xlinker --gc-sections)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.gcsections" useByScannerDiscovery="false" value="true" valueType="boolean"/>
-								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile.675234327" name="Script files (-T)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile" useByScannerDiscovery="false" valueType="stringList">
+								<option IS_BUILTIN_EMPTY="false" IS_VALUE_EMPTY="false" id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile.675234327" name="Script files (-T)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.scriptfile" useByScannerDiscovery="false" valueType="stringList">
 									<listOptionValue builtIn="false" value="&quot;${workspace_loc:/${ProjName}/STM32L433CCUx_FLASH.ld}&quot;"/>
 								</option>
 								<option id="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.nostdlibs.1855020595" name="No startup or default libs (-nostdlib)" superClass="ilg.gnuarmeclipse.managedbuild.cross.option.cpp.linker.nostdlibs" useByScannerDiscovery="false" value="false" valueType="boolean"/>
diff --git a/.settings/language.settings.xml b/.settings/language.settings.xml
index b29c417..3d08f16 100644
--- a/.settings/language.settings.xml
+++ b/.settings/language.settings.xml
@@ -3,7 +3,7 @@
 	<configuration id="ilg.gnuarmeclipse.managedbuild.cross.config.elf.debug.1309195742.6250637" name="ARM_Debug">
 		<extension point="org.eclipse.cdt.core.LanguageSettingsProvider">
 			<provider copy-of="extension" id="org.eclipse.cdt.ui.UserLanguageSettingsProvider"/>
-			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="793420653061" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
+			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="-1332118872860258658" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
 				<language-scope id="org.eclipse.cdt.core.gcc"/>
 				<language-scope id="org.eclipse.cdt.core.g++"/>
 			</provider>
@@ -14,7 +14,7 @@
 	<configuration id="ilg.gnuarmeclipse.managedbuild.cross.config.elf.debug.1309195742.6250637.815824991" name="ARM_Release">
 		<extension point="org.eclipse.cdt.core.LanguageSettingsProvider">
 			<provider copy-of="extension" id="org.eclipse.cdt.ui.UserLanguageSettingsProvider"/>
-			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="793420653061" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
+			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="-1246452000316836338" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
 				<language-scope id="org.eclipse.cdt.core.gcc"/>
 				<language-scope id="org.eclipse.cdt.core.g++"/>
 			</provider>

From 4223b6085e7bf83e15821841a65f94f10bc40383 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Mon, 24 Feb 2020 22:40:26 -0600
Subject: [PATCH 23/36] Update version to 2.0.0rc1.

---
 TNC/KissHardware.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index 392c696..d3a55cc 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -29,7 +29,7 @@ int powerOffViaUSB(void)
 
 namespace mobilinkd { namespace tnc { namespace kiss {
 
-const char FIRMWARE_VERSION[] = "2.0.0b3";
+const char FIRMWARE_VERSION[] = "2.0.0rc1";
 const char HARDWARE_VERSION[] = "Mobilinkd TNC3 2.1.1";
 
 

From b320c4a041c0b05ec0ead225c46c8e4b2bb3a77f Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Thu, 27 Feb 2020 11:17:58 -0600
Subject: [PATCH 24/36] Experimental FSK change for K7FR.

---
 TNC/Fsk9600Demodulator.hpp | 2 +-
 TNC/Fsk9600Modulator.cpp   | 7 +++++++
 TNC/KissHardware.cpp       | 2 +-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/TNC/Fsk9600Demodulator.hpp b/TNC/Fsk9600Demodulator.hpp
index 4a57f5d..5abe2dd 100644
--- a/TNC/Fsk9600Demodulator.hpp
+++ b/TNC/Fsk9600Demodulator.hpp
@@ -70,7 +70,7 @@ struct Fsk9600Demodulator : IDemodulator
         sConfig.Channel = AUDIO_IN;
         sConfig.Rank = ADC_REGULAR_RANK_1;
         sConfig.SingleDiff = ADC_SINGLE_ENDED;
-        sConfig.SamplingTime = ADC_SAMPLETIME_92CYCLES_5;
+        sConfig.SamplingTime = ADC_SAMPLETIME_247CYCLES_5;
         sConfig.OffsetNumber = ADC_OFFSET_NONE;
         sConfig.Offset = 0;
         if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
diff --git a/TNC/Fsk9600Modulator.cpp b/TNC/Fsk9600Modulator.cpp
index 1f5d4ac..e04f2c0 100644
--- a/TNC/Fsk9600Modulator.cpp
+++ b/TNC/Fsk9600Modulator.cpp
@@ -5,10 +5,17 @@
 
 namespace mobilinkd { namespace tnc {
 
+/*
 const Fsk9600Modulator::cos_table_type Fsk9600Modulator::cos_table = {
     2047,  2020,  1937,  1801,  1616,  1387,  1120,   822,   502,   169,
     -169,  -502,  -822, -1120, -1387, -1616, -1801, -1937, -2020, -2048
 };
+*/
+
+const Fsk9600Modulator::cos_table_type Fsk9600Modulator::cos_table = {
+     2047,  2047,  2047,  2047,  2047,  2047,  2047,  2047,  2047,  2047,
+    -2048, -2048, -2048, -2048, -2048, -2048, -2048, -2048, -2048, -2048
+};
 
 void Fsk9600Modulator::init(const kiss::Hardware& hw)
 {
diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index d3a55cc..1fe5994 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -29,7 +29,7 @@ int powerOffViaUSB(void)
 
 namespace mobilinkd { namespace tnc { namespace kiss {
 
-const char FIRMWARE_VERSION[] = "2.0.0rc1";
+const char FIRMWARE_VERSION[] = "2.0.0ex1"; // for KF7R testing
 const char HARDWARE_VERSION[] = "Mobilinkd TNC3 2.1.1";
 
 

From a06d3b694b5c5d8011cae860fef4fe3c24415b28 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Thu, 5 Mar 2020 20:22:37 -0600
Subject: [PATCH 25/36] Enable sample&hold on DAC channel 2.  Log when changing
 frequency.

---
 Src/main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Src/main.c b/Src/main.c
index 02a224e..92ddd7a 100644
--- a/Src/main.c
+++ b/Src/main.c
@@ -60,6 +60,7 @@
 #include "bm78.h"
 #include "base64.h"
 #include "KissHardware.h"
+#include "Log.h"
 
 /* USER CODE END Includes */
 
@@ -905,6 +906,7 @@ static void MX_DAC1_Init(void)
     */
   sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
   sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
+  sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_ENABLE;
   if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_2) != HAL_OK)
   {
     _Error_Handler(__FILE__, __LINE__);
@@ -1455,6 +1457,8 @@ void SysClock48()
 
     if (HAL_RCC_GetHCLKFreq() == 48000000) return;
 
+    INFO("Setting 48MHz SysClock.");
+
     RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
     RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
 
@@ -1500,6 +1504,8 @@ void SysClock80()
 
     if (HAL_RCC_GetHCLKFreq() == 80000000) return;
 
+    INFO("Setting 80MHz SysClock.");
+
     RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
     RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
 

From 7b721c0d6b081ec650bac391c1e2535e9555c991 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Thu, 5 Mar 2020 20:28:45 -0600
Subject: [PATCH 26/36] Fix hang when starting in 9600 baud mode.  Change to
 non-symmetric GMSK waveform.

---
 TNC/AFSKModulator.cpp      |  6 +-----
 TNC/Fsk9600Demodulator.hpp |  1 -
 TNC/Fsk9600Modulator.cpp   | 16 +++++++++++-----
 TNC/Fsk9600Modulator.hpp   |  4 ++--
 4 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/TNC/AFSKModulator.cpp b/TNC/AFSKModulator.cpp
index e169216..d4d1c66 100644
--- a/TNC/AFSKModulator.cpp
+++ b/TNC/AFSKModulator.cpp
@@ -9,11 +9,7 @@ void AFSKModulator::init(const kiss::Hardware& hw)
 {
     set_twist(hw.tx_twist);
 
-    if (HAL_RCC_GetHCLKFreq() != 48000000)
-    {
-        ERROR("Clock is not 48MHz");
-        CxxErrorHandler();
-    }
+    SysClock48();
 
     // Configure 48MHz clock for 26.4ksps.
     htim7.Init.Period = 1817;
diff --git a/TNC/Fsk9600Demodulator.hpp b/TNC/Fsk9600Demodulator.hpp
index 5abe2dd..a4ce20d 100644
--- a/TNC/Fsk9600Demodulator.hpp
+++ b/TNC/Fsk9600Demodulator.hpp
@@ -51,7 +51,6 @@ struct Fsk9600Demodulator : IDemodulator
 
     void start() override
     {
-        INFO("Setting 80MHz SysClock.");
         SysClock80();
 
         auto const& bpf_coeffs = bpf_bank[kiss::settings().rx_twist + 3];
diff --git a/TNC/Fsk9600Modulator.cpp b/TNC/Fsk9600Modulator.cpp
index e04f2c0..2f2d7b7 100644
--- a/TNC/Fsk9600Modulator.cpp
+++ b/TNC/Fsk9600Modulator.cpp
@@ -6,16 +6,26 @@
 namespace mobilinkd { namespace tnc {
 
 /*
+ * Cosine.
 const Fsk9600Modulator::cos_table_type Fsk9600Modulator::cos_table = {
     2047,  2020,  1937,  1801,  1616,  1387,  1120,   822,   502,   169,
     -169,  -502,  -822, -1120, -1387, -1616, -1801, -1937, -2020, -2048
 };
 */
 
+/*
+ * Square wave -- filtered in hardware at 7200Hz
 const Fsk9600Modulator::cos_table_type Fsk9600Modulator::cos_table = {
      2047,  2047,  2047,  2047,  2047,  2047,  2047,  2047,  2047,  2047,
     -2048, -2048, -2048, -2048, -2048, -2048, -2048, -2048, -2048, -2048
 };
+*/
+
+// Gaussian
+const Fsk9600Modulator::cos_table_type Fsk9600Modulator::cos_table = {
+    2042,  2027,  1995,  1931,  1815,  1626,  1345,   968,   507,     0,
+    -507,  -968, -1345, -1626, -1815, -1931, -1995, -2027, -2042, -2048
+};
 
 void Fsk9600Modulator::init(const kiss::Hardware& hw)
 {
@@ -26,11 +36,7 @@ void Fsk9600Modulator::init(const kiss::Hardware& hw)
     state = State::STOPPED;
     level = Level::HIGH;
 
-    if (HAL_RCC_GetHCLKFreq() != 80000000)
-    {
-        ERROR("Clock is not 80MHz");
-        CxxErrorHandler();
-    }
+    SysClock80();
 
     // Configure 80MHz clock for 192ksps.
     htim7.Init.Period = 416;
diff --git a/TNC/Fsk9600Modulator.hpp b/TNC/Fsk9600Modulator.hpp
index aceeaf9..5bc53d2 100644
--- a/TNC/Fsk9600Modulator.hpp
+++ b/TNC/Fsk9600Modulator.hpp
@@ -211,8 +211,8 @@ private:
         case Level::LOW:
             if (bit)
             {
-                std::transform(cos_table.rbegin(), cos_table.rend(), buffer,
-                    [this](auto x){return adjust_level(x);});
+                std::transform(cos_table.begin(), cos_table.end(), buffer,
+                    [this](auto x){return adjust_level(-1 - x);});
                 level = Level::HIGH;
             }
             else

From eceaee124b17d2fb04b42f49ca2c534724569b04 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Thu, 5 Mar 2020 20:29:30 -0600
Subject: [PATCH 27/36] Change IDLE to FLAG (testing; req'd per AX.25).

---
 TNC/HDLCEncoder.hpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/TNC/HDLCEncoder.hpp b/TNC/HDLCEncoder.hpp
index 355f679..4e90897 100644
--- a/TNC/HDLCEncoder.hpp
+++ b/TNC/HDLCEncoder.hpp
@@ -25,8 +25,9 @@ using namespace mobilinkd::libafsk;
 
 struct Encoder {
 
-    static const uint8_t IDLE = 0x00;
-    static const uint8_t FLAG = 0x7E;
+    // static constexpr uint8_t IDLE = 0x00;
+    static constexpr uint8_t IDLE = 0x7E;
+    static constexpr uint8_t FLAG = 0x7E;
 
     enum class state_type {
         STATE_IDLE,

From a78c3df3237a35ab8fd36b9dfd59673ed9281a03 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Thu, 5 Mar 2020 20:30:13 -0600
Subject: [PATCH 28/36] Loosen DCD requirement for decode.

---
 TNC/HdlcDecoder.cpp | 23 +++++++++++------------
 TNC/HdlcDecoder.hpp | 10 ++++++++++
 2 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/TNC/HdlcDecoder.cpp b/TNC/HdlcDecoder.cpp
index 44da02e..0f922ed 100644
--- a/TNC/HdlcDecoder.cpp
+++ b/TNC/HdlcDecoder.cpp
@@ -38,7 +38,7 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
         if (!packet) osThreadYield();
     }
 
-    if (pll_lock) {
+    if (pll_lock or dcd != DCD::ON) {
         if (ones == 5) {
             if (input) {
                 // flag byte
@@ -51,6 +51,8 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
             }
         }
 
+        had_dcd |= pll_lock;
+
         buffer >>= 1;
         buffer |= (input * 128);
         bits += 1;                      // Free-running until Sync byte.
@@ -63,14 +65,14 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
         if (flag) {
             switch (buffer) {
             case 0x7E:
-                if (packet->size() > 2) {
+                if (packet->size() > 14) {
                     // We have started decoding a packet.
                     packet->parse_fcs();
                     report_bits = bits;
-                    if (packet->size() < 15) {
+                    if (dcd == DCD::PARTIAL and not had_dcd) {
                         // 120 (136) bits per AX.25 section 3.9.
                         // Note we discard the flags.
-                        result_code = STATUS_FRAME_ERROR;
+                        result_code = STATUS_NO_CARRIER;
                     } else if (packet->ok()) {
                         // Not compliant with AX.25 section 3.9.
                         // We ignore byte alignment when FCS is OK.
@@ -92,6 +94,7 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
                 state = State::SYNC;
                 flag = 0;
                 bits = 0;
+                had_dcd = false;
                 break;
             case 0xFE:
                 if (packet->size()) {
@@ -133,15 +136,11 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
         // PLL unlocked.
         // Note the rules here are the same as above.
         report_bits = bits;
-        if (packet->size() > 2)
+        had_dcd = false;
+        if (packet->size() > 14)
         {
             packet->parse_fcs();
-            if (packet->size() < 15) {
-                // 120 (136) bits per AX.25 section 3.9.
-                // Note we discard the flags.
-                result_code = STATUS_NO_CARRIER;
-            }
-            else if (packet->ok())
+            if (packet->ok())
             {
                 // Not compliant with AX.25 section 3.9.
                 // We ignore byte alignment when FCS is OK.
@@ -159,7 +158,7 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
         }
         else
         {
-            result_code = STATUS_NO_CARRIER;
+            packet->clear();
         }
 
         if (state != State::IDLE) {
diff --git a/TNC/HdlcDecoder.hpp b/TNC/HdlcDecoder.hpp
index bece5f2..2307dd5 100644
--- a/TNC/HdlcDecoder.hpp
+++ b/TNC/HdlcDecoder.hpp
@@ -33,6 +33,7 @@ struct NewDecoder
     uint8_t report_bits{0};
     uint8_t ones{0};
     bool flag{0};
+    bool had_dcd{false};
 
     /**
      * Tell the demodulator to return all "passable" HDLC frames.  These
@@ -41,6 +42,10 @@ struct NewDecoder
      */
     bool passall{false};
 
+    enum class DCD { ON, PARTIAL, OFF };
+
+    DCD dcd{DCD::PARTIAL};
+
     frame_type* packet{nullptr};
 
     NewDecoder(bool pass_all=false)
@@ -58,6 +63,11 @@ struct NewDecoder
     {
         passall = enabled;
     }
+
+    void setDCD(DCD config)
+    {
+        dcd = config;
+    }
 };
 
 }}} // mobilinkd::tnc::hdlc

From 2c4820ac48a300edc7108523cd59969b14e1baeb Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Thu, 5 Mar 2020 20:30:43 -0600
Subject: [PATCH 29/36] Update to version 2.0.0ex2.

---
 TNC/KissHardware.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index 1fe5994..bd8f67e 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -29,7 +29,7 @@ int powerOffViaUSB(void)
 
 namespace mobilinkd { namespace tnc { namespace kiss {
 
-const char FIRMWARE_VERSION[] = "2.0.0ex1"; // for KF7R testing
+const char FIRMWARE_VERSION[] = "2.0.0ex2"; // for KF7R testing
 const char HARDWARE_VERSION[] = "Mobilinkd TNC3 2.1.1";
 
 

From f84a4a289edc86cdae934c7410d142162a67a42e Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Tue, 14 Apr 2020 19:30:34 -0500
Subject: [PATCH 30/36] Minor whitespace changes.

---
 TNC/AFSKModulator.hpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/TNC/AFSKModulator.hpp b/TNC/AFSKModulator.hpp
index d772d38..a6c80c9 100644
--- a/TNC/AFSKModulator.hpp
+++ b/TNC/AFSKModulator.hpp
@@ -117,6 +117,7 @@ struct AFSKModulator : Modulator
             #ifdef KISS_LOGGING
                 HAL_RCCEx_DisableLSCO();
             #endif
+
             fill_first(bit);
             running_ = 0;
             break;
@@ -202,7 +203,7 @@ struct AFSKModulator : Modulator
 
         // Drain the queue.
         while (osMessageGet(dacOutputQueueHandle_, 0).status == osEventMessage);
-    }
+   }
 
    float bits_per_ms() const override
    {

From 6420bd4f58ef6f6157a2882fdc7b0cc7843433eb Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Tue, 14 Apr 2020 21:02:15 -0500
Subject: [PATCH 31/36] Add StdDev/SNR calc for debug.

---
 .settings/language.settings.xml |  4 +--
 Src/main.c                      |  8 +++--
 TNC/Fsk9600Demodulator.cpp      | 24 ++++++++++++++
 TNC/Fsk9600Demodulator.hpp      |  3 ++
 TNC/HDLCEncoder.hpp             |  1 +
 TNC/HdlcDecoder.hpp             |  5 +++
 TNC/KissHardware.cpp            |  2 +-
 TNC/KissHardware.hpp            |  4 +++
 TNC/StandardDeviation.hpp       | 59 +++++++++++++++++++++++++++++++++
 stlink-tnc3.cfg                 |  2 +-
 10 files changed, 105 insertions(+), 7 deletions(-)
 create mode 100644 TNC/StandardDeviation.hpp

diff --git a/.settings/language.settings.xml b/.settings/language.settings.xml
index 3d08f16..8fe73b1 100644
--- a/.settings/language.settings.xml
+++ b/.settings/language.settings.xml
@@ -3,7 +3,7 @@
 	<configuration id="ilg.gnuarmeclipse.managedbuild.cross.config.elf.debug.1309195742.6250637" name="ARM_Debug">
 		<extension point="org.eclipse.cdt.core.LanguageSettingsProvider">
 			<provider copy-of="extension" id="org.eclipse.cdt.ui.UserLanguageSettingsProvider"/>
-			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="-1332118872860258658" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
+			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="-875080106735501948" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
 				<language-scope id="org.eclipse.cdt.core.gcc"/>
 				<language-scope id="org.eclipse.cdt.core.g++"/>
 			</provider>
@@ -14,7 +14,7 @@
 	<configuration id="ilg.gnuarmeclipse.managedbuild.cross.config.elf.debug.1309195742.6250637.815824991" name="ARM_Release">
 		<extension point="org.eclipse.cdt.core.LanguageSettingsProvider">
 			<provider copy-of="extension" id="org.eclipse.cdt.ui.UserLanguageSettingsProvider"/>
-			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="-1246452000316836338" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
+			<provider class="org.eclipse.cdt.managedbuilder.language.settings.providers.GCCBuiltinSpecsDetector" console="false" env-hash="-789413234192079628" id="ilg.gnuarmeclipse.managedbuild.cross.GCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT ARM Cross GCC Built-in Compiler Settings " parameter="${COMMAND} ${FLAGS} ${cross_toolchain_flags} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
 				<language-scope id="org.eclipse.cdt.core.gcc"/>
 				<language-scope id="org.eclipse.cdt.core.g++"/>
 			</provider>
diff --git a/Src/main.c b/Src/main.c
index 92ddd7a..d1bdce7 100644
--- a/Src/main.c
+++ b/Src/main.c
@@ -895,7 +895,7 @@ static void MX_DAC1_Init(void)
   sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
   sConfig.DAC_Trigger = DAC_TRIGGER_T7_TRGO;
   sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
-  sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
+  sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_DISABLE;
   sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
   if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)
   {
@@ -904,9 +904,11 @@ static void MX_DAC1_Init(void)
 
     /**DAC channel OUT2 config 
     */
+  sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
   sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
-  sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_ENABLE;
-  sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_ENABLE;
+  sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
+  sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_DISABLE;
+  sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
   if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_2) != HAL_OK)
   {
     _Error_Handler(__FILE__, __LINE__);
diff --git a/TNC/Fsk9600Demodulator.cpp b/TNC/Fsk9600Demodulator.cpp
index 18e198a..187bdcf 100644
--- a/TNC/Fsk9600Demodulator.cpp
+++ b/TNC/Fsk9600Demodulator.cpp
@@ -5,6 +5,7 @@
 #include "Goertzel.h"
 #include "AudioInput.hpp"
 #include "GPIO.hpp"
+#include "Log.h"
 
 namespace mobilinkd { namespace tnc {
 
@@ -32,8 +33,31 @@ hdlc::IoFrame* Fsk9600Demodulator::operator()(const q15_t* samples)
                 if (tmp) hdlc::release(tmp);
             } else {
                 result = hdlc_decoder_(nrzi_.decode(lfsr_(bit)), locked_);
+#ifdef KISS_LOGGING
+                if (result) {
+                    INFO("samples = %ld, mean = %d, dev = %d",
+                        snr_.samples, int(snr_.mean), int(snr_.stdev()));
+                    INFO("SNR = %dmB", int(snr_.SNR() * 100.0f));
+                    snr_.reset();
+                }
+#endif
             }
+
+#ifdef KISS_LOGGING
+            if (hdlc_decoder_.active())
+            {
+                if (!decoding_)
+                {
+                    snr_.reset();
+                    decoding_ = true;
+                }
+                snr_.capture(float(abs(sample)));
+            } else {
+                decoding_ = false;
+            }
+#endif
         }
+
     }
     return result;
 }
diff --git a/TNC/Fsk9600Demodulator.hpp b/TNC/Fsk9600Demodulator.hpp
index a4ce20d..3e914c2 100644
--- a/TNC/Fsk9600Demodulator.hpp
+++ b/TNC/Fsk9600Demodulator.hpp
@@ -10,6 +10,7 @@
 #include "NRZI.hpp"
 #include "HdlcDecoder.hpp"
 #include "KissHardware.hpp"
+#include "StandardDeviation.hpp"
 
 namespace mobilinkd { namespace tnc {
 
@@ -46,6 +47,8 @@ struct Fsk9600Demodulator : IDemodulator
     Descrambler lfsr_;
     libafsk::NRZI nrzi_;
     hdlc::NewDecoder hdlc_decoder_;
+    StandardDeviation snr_;
+    bool decoding_{false};
 
     virtual ~Fsk9600Demodulator() {}
 
diff --git a/TNC/HDLCEncoder.hpp b/TNC/HDLCEncoder.hpp
index 4e90897..079fe9c 100644
--- a/TNC/HDLCEncoder.hpp
+++ b/TNC/HDLCEncoder.hpp
@@ -205,6 +205,7 @@ struct Encoder {
 
     void send_delay() {
         const size_t tmp = tx_delay_ * 1.25 * modulator_->bits_per_ms();
+
         INFO("Sending %u IDLE bytes", tmp);
         for (size_t i = 0; i != tmp; i++) {
             send_raw(IDLE);
diff --git a/TNC/HdlcDecoder.hpp b/TNC/HdlcDecoder.hpp
index 2307dd5..aa971d3 100644
--- a/TNC/HdlcDecoder.hpp
+++ b/TNC/HdlcDecoder.hpp
@@ -68,6 +68,11 @@ struct NewDecoder
     {
         dcd = config;
     }
+
+    bool active() const
+    {
+        return state != State::IDLE;
+    }
 };
 
 }}} // mobilinkd::tnc::hdlc
diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index bd8f67e..8ad3618 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -112,7 +112,7 @@ void reply16(uint8_t cmd, uint16_t result) {
     ioport->write(data, 3, 6, osWaitForever);
 }
 
-inline void reply(uint8_t cmd, const uint8_t* data, uint16_t len) {
+void reply(uint8_t cmd, const uint8_t* data, uint16_t len) {
     uint8_t* buffer = static_cast<uint8_t*>(alloca(len + 1));
     buffer[0] = cmd;
     for (uint16_t i = 0; i != len; i++)
diff --git a/TNC/KissHardware.hpp b/TNC/KissHardware.hpp
index 1dc3bbb..0533d6b 100644
--- a/TNC/KissHardware.hpp
+++ b/TNC/KissHardware.hpp
@@ -105,6 +105,8 @@ constexpr const uint8_t GET_MAC_ADDRESS = 48;
 constexpr const uint8_t GET_DATETIME = 49;
 constexpr const uint8_t SET_DATETIME = 50;
 constexpr const uint8_t GET_ERROR_MSG = 51;
+constexpr const uint8_t GET_SNR = 52;
+constexpr const uint8_t GET_BER = 53;
 
 constexpr const uint8_t SET_BLUETOOTH_NAME = 65;
 constexpr const uint8_t GET_BLUETOOTH_NAME = 66;
@@ -402,4 +404,6 @@ void reply8(uint8_t cmd, uint8_t result) __attribute__((noinline));
 
 void reply16(uint8_t cmd, uint16_t result) __attribute__((noinline));
 
+void reply(uint8_t cmd, const uint8_t* data, uint16_t len) __attribute__((noinline));
+
 }}} // mobilinkd::tnc::kiss
diff --git a/TNC/StandardDeviation.hpp b/TNC/StandardDeviation.hpp
new file mode 100644
index 0000000..e014476
--- /dev/null
+++ b/TNC/StandardDeviation.hpp
@@ -0,0 +1,59 @@
+// Copyright 2020 Mobilinkd LLC <rob@mobilinkd.com>
+// All rights reserved.
+
+#pragma once
+
+#include "main.h"
+
+#include <arm_math.h>
+
+#include <cstdint>
+
+namespace mobilinkd {
+
+/**
+ * Compute a running standard deviation.
+ *
+ * Based on https://dsp.stackexchange.com/a/1187/36581
+ */
+struct StandardDeviation
+{
+    float mean{0.0};
+    float S{0.0};
+    uint32_t samples{0};
+
+    void reset()
+    {
+        mean = 0.0;
+        S = 0.0;
+        samples = 0;
+    }
+
+    void capture(float sample)
+    {
+        auto prev = mean;
+        samples += 1;
+        mean = mean + (sample - mean) / samples;
+        S = S + (sample - mean) * (sample - prev);
+    }
+
+    float variance() const
+    {
+        return samples == 0 ? -1.0 :  S / samples;
+    }
+
+    float stdev() const
+    {
+        float result = -1.0;
+        arm_sqrt_f32(variance(), &result);
+        return result;
+    }
+
+    // SNR in dB
+    float SNR() const
+    {
+        return 10.0 * log10(mean / stdev());
+    }
+};
+
+} // mobilinkd
diff --git a/stlink-tnc3.cfg b/stlink-tnc3.cfg
index adcea77..19fd821 100644
--- a/stlink-tnc3.cfg
+++ b/stlink-tnc3.cfg
@@ -9,4 +9,4 @@ source [find target/stm32l4x.cfg]
 
 reset_config srst_only
 itm port 0 on
-tpiu config internal swv uart off 48000000
+tpiu config internal swv uart off 80000000

From e7ac9c4307e8f99bd999640bf4da87bdce7c48ae Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Fri, 17 Apr 2020 16:37:50 -0500
Subject: [PATCH 32/36] Update version to 2.0.0ex3

---
 TNC/KissHardware.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index 8ad3618..29dd9f1 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -29,7 +29,7 @@ int powerOffViaUSB(void)
 
 namespace mobilinkd { namespace tnc { namespace kiss {
 
-const char FIRMWARE_VERSION[] = "2.0.0ex2"; // for KF7R testing
+const char FIRMWARE_VERSION[] = "2.0.0ex3"; // for KF7R testing
 const char HARDWARE_VERSION[] = "Mobilinkd TNC3 2.1.1";
 
 

From 4813a134260056efa6ff28177eb8ffe94196c342 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sun, 19 Apr 2020 21:03:22 -0500
Subject: [PATCH 33/36] Update release version to v2.0.0.

---
 TNC/KissHardware.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index 29dd9f1..9da9123 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -29,7 +29,7 @@ int powerOffViaUSB(void)
 
 namespace mobilinkd { namespace tnc { namespace kiss {
 
-const char FIRMWARE_VERSION[] = "2.0.0ex3"; // for KF7R testing
+const char FIRMWARE_VERSION[] = "2.0.0";
 const char HARDWARE_VERSION[] = "Mobilinkd TNC3 2.1.1";
 
 

From 88436fbd2a99a86b15ef0c2c9a66c567582c0cdf Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Fri, 3 Jul 2020 19:08:02 -0500
Subject: [PATCH 34/36] Increase USB input queue size.  Change iterator tag on
 slip encoder.  Avoid potential undefind behavior in SLIP code. Send
 additional flag when transmitting back to back frames.  Reduce minimum frame
 size.  Update version to 2.0.1.

---
 TNC/HDLCEncoder.hpp  |  2 ++
 TNC/HdlcDecoder.cpp  |  4 ++--
 TNC/Kiss.hpp         | 28 ++++++++++++----------------
 TNC/KissHardware.cpp |  2 +-
 TNC/UsbPort.cpp      |  2 +-
 5 files changed, 18 insertions(+), 20 deletions(-)

diff --git a/TNC/HDLCEncoder.hpp b/TNC/HDLCEncoder.hpp
index 079fe9c..43826ac 100644
--- a/TNC/HDLCEncoder.hpp
+++ b/TNC/HDLCEncoder.hpp
@@ -196,6 +196,8 @@ struct Encoder {
             }
             send_delay();
             send_delay_ = false;
+        } else {
+            send_raw(FLAG);
         }
 
         for (auto c : *frame) send(c);
diff --git a/TNC/HdlcDecoder.cpp b/TNC/HdlcDecoder.cpp
index 0f922ed..1ff731a 100644
--- a/TNC/HdlcDecoder.cpp
+++ b/TNC/HdlcDecoder.cpp
@@ -65,7 +65,7 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
         if (flag) {
             switch (buffer) {
             case 0x7E:
-                if (packet->size() > 14) {
+                if (packet->size() > 2) {
                     // We have started decoding a packet.
                     packet->parse_fcs();
                     report_bits = bits;
@@ -137,7 +137,7 @@ uint8_t NewDecoder::process(bool input, bool pll_lock)
         // Note the rules here are the same as above.
         report_bits = bits;
         had_dcd = false;
-        if (packet->size() > 14)
+        if (packet->size() > 2)
         {
             packet->parse_fcs();
             if (packet->ok())
diff --git a/TNC/Kiss.hpp b/TNC/Kiss.hpp
index eda3273..a07959c 100644
--- a/TNC/Kiss.hpp
+++ b/TNC/Kiss.hpp
@@ -46,9 +46,7 @@ struct slip_encoder
 
     slip_encoder()
     : packet_(0), size_(0), pos_(0), current_(0), shifting_(false)
-    {
-        set_current();
-    }
+    {}
 
     slip_encoder(const char* packet, size_t len)
     : packet_(packet), size_(len), pos_(0), current_(0), shifting_(false)
@@ -108,23 +106,23 @@ struct slip_encoder
 };
 
 /**
- * This is a forward iterator adapter that SLIP-encodes the data from the
+ * This is a input iterator adapter that SLIP-encodes the data from the
  * underlying frame iterator.  The only requirement is that the underlying
- * iterator meets the requirements of a forward iterator and that its value
+ * iterator meets the requirements of an input iterator and that its value
  * type is convertible to char.
  */
 struct slip_encoder2
 {
-    typedef std::forward_iterator_tag iterator_category;
+    typedef std::input_iterator_tag iterator_category;
     typedef size_t difference_type;
     typedef char value_type;
     typedef char& reference;
     typedef char* pointer;
 
-    static const uint8_t FEND = 0xC0;
-    static const uint8_t FESC = 0xDB;
-    static const uint8_t TFEND = 0xDC;
-    static const uint8_t TFESC = 0xDD;
+    static const char FEND = 0xC0;
+    static const char FESC = 0xDB;
+    static const char TFEND = 0xDC;
+    static const char TFESC = 0xDD;
 
     hdlc::IoFrame::iterator iter_;
     mutable bool shifting_;
@@ -161,7 +159,7 @@ struct slip_encoder2
      * @return the slip-encoded character.
      */
     char operator*() const {
-        uint8_t c = *iter_;
+        char c = *iter_;
 
         if (shifting_) {
             return c == FEND ? TFEND : TFESC;
@@ -171,7 +169,7 @@ struct slip_encoder2
             return FESC;
         }
 
-        return *iter_;
+        return c;
     }
 
     /**
@@ -192,7 +190,7 @@ struct slip_encoder2
      * @return a reference to *this.
      */
     slip_encoder2& operator++() {
-        uint8_t c = *iter_;
+        char c = *iter_;
         if (not shifting_ and ((c == FEND) or (c == FESC))) {
             shifting_ = true;
             return *this;
@@ -238,9 +236,7 @@ struct slip_decoder
 
     slip_decoder()
     : packet_(0), size_(0), pos_(0), current_(0)
-    {
-        set_current();
-    }
+    {}
 
     slip_decoder(const char* packet, size_t len)
     : packet_(packet), size_(len), pos_(0), current_(0)
diff --git a/TNC/KissHardware.cpp b/TNC/KissHardware.cpp
index 9da9123..5d26539 100644
--- a/TNC/KissHardware.cpp
+++ b/TNC/KissHardware.cpp
@@ -29,7 +29,7 @@ int powerOffViaUSB(void)
 
 namespace mobilinkd { namespace tnc { namespace kiss {
 
-const char FIRMWARE_VERSION[] = "2.0.0";
+const char FIRMWARE_VERSION[] = "2.0.1";
 const char HARDWARE_VERSION[] = "Mobilinkd TNC3 2.1.1";
 
 
diff --git a/TNC/UsbPort.cpp b/TNC/UsbPort.cpp
index b9620e6..b3d39a6 100644
--- a/TNC/UsbPort.cpp
+++ b/TNC/UsbPort.cpp
@@ -151,7 +151,7 @@ void UsbPort::init()
 {
     if (cdcTaskHandle_) return;
 
-    osMessageQDef(cdcQueue, 4, void*);
+    osMessageQDef(cdcQueue, 128, void*);
     queue_ = osMessageCreate(osMessageQ(cdcQueue), 0);
 
     osMutexDef(usbMutex);

From 98ceec25591b41459a6e28f470fd203c834bd4f4 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sat, 4 Jul 2020 14:45:20 -0500
Subject: [PATCH 35/36] Use a ping-pong buffer for USB RX.  Simplify code and
 improve flow control.

---
 Inc/usbd_cdc_if.h | 15 +++++++++++
 Src/usbd_cdc_if.c | 23 ++++++-----------
 TNC/UsbPort.cpp   | 64 +++++++++++++++++++----------------------------
 3 files changed, 49 insertions(+), 53 deletions(-)

diff --git a/Inc/usbd_cdc_if.h b/Inc/usbd_cdc_if.h
index 140c224..bd7a0fd 100644
--- a/Inc/usbd_cdc_if.h
+++ b/Inc/usbd_cdc_if.h
@@ -78,6 +78,9 @@
   */
 /* USER CODE BEGIN EXPORTED_DEFINES */
 
+#define APP_RX_DATA_SIZE  64
+#define APP_TX_DATA_SIZE  64
+
 /* USER CODE END EXPORTED_DEFINES */
 
 /**
@@ -91,6 +94,14 @@
 
 /* USER CODE BEGIN EXPORTED_TYPES */
 
+struct UsbCdcRxBuffer
+{
+    uint8_t buffer[APP_RX_DATA_SIZE];
+    uint32_t size;
+};
+
+typedef struct UsbCdcRxBuffer UsbCdcRxBuffer_t;
+
 /* USER CODE END EXPORTED_TYPES */
 
 /**
@@ -120,6 +131,10 @@ extern USBD_CDC_ItfTypeDef USBD_Interface_fops_FS;
 
 /* USER CODE BEGIN EXPORTED_VARIABLES */
 
+// USB CDC receive ping pong buffer.
+extern UsbCdcRxBuffer_t* usbCdcRxBuffer_1;
+extern UsbCdcRxBuffer_t* usbCdcRxBuffer_2;
+
 /* USER CODE END EXPORTED_VARIABLES */
 
 /**
diff --git a/Src/usbd_cdc_if.c b/Src/usbd_cdc_if.c
index 583ee90..2e36f0e 100644
--- a/Src/usbd_cdc_if.c
+++ b/Src/usbd_cdc_if.c
@@ -97,8 +97,6 @@
 /* USER CODE BEGIN PRIVATE_DEFINES */
 /* Define size for the receive and transmit buffer over CDC */
 /* It's up to user to redefine and/or remove those define */
-#define APP_RX_DATA_SIZE  64
-#define APP_TX_DATA_SIZE  64
 /* USER CODE END PRIVATE_DEFINES */
 
 /**
@@ -124,8 +122,6 @@
   */
 /* Create buffer for reception and transmission           */
 /* It's up to user to redefine and/or remove those define */
-/** Received data over USB are stored in this buffer      */
-uint8_t UserRxBufferFS[APP_RX_DATA_SIZE];
 
 /** Data to send over USB CDC are stored in this buffer   */
 uint8_t UserTxBufferFS[APP_TX_DATA_SIZE];
@@ -138,6 +134,11 @@ USBD_CDC_LineCodingTypeDef LineCoding = {
     0x08    // number of bits: 8
 };
 
+// USB CDC receive ping pong buffer.
+UsbCdcRxBuffer_t usbCdcRxBuffer[2];
+UsbCdcRxBuffer_t* usbCdcRxBuffer_1 = &usbCdcRxBuffer[0];
+UsbCdcRxBuffer_t* usbCdcRxBuffer_2 = &usbCdcRxBuffer[1];
+
 /* USER CODE END PRIVATE_VARIABLES */
 
 /**
@@ -195,7 +196,7 @@ static int8_t CDC_Init_FS(void)
   /* USER CODE BEGIN 3 */
   /* Set Application Buffers */
   USBD_CDC_SetTxBuffer(&hUsbDeviceFS, UserTxBufferFS, 0);
-  USBD_CDC_SetRxBuffer(&hUsbDeviceFS, UserRxBufferFS);
+  USBD_CDC_SetRxBuffer(&hUsbDeviceFS, usbCdcRxBuffer_1->buffer);
   return (USBD_OK);
   /* USER CODE END 3 */
 }
@@ -304,12 +305,6 @@ static int8_t CDC_Control_FS(uint8_t cmd, uint8_t* pbuf, uint16_t length)
   * @brief  Data received over USB OUT endpoint are sent over CDC interface
   *         through this function.
   *
-  *         @note
-  *         This function will block any OUT packet reception on USB endpoint
-  *         until exiting this function. If you exit this function before transfer
-  *         is complete on CDC interface (ie. using DMA controller) it will result
-  *         in receiving more data while previous ones are still not sent.
-  *
   * @param  Buf: Buffer of data to be received
   * @param  Len: Number of data received (in bytes)
   * @retval Result of the operation: USBD_OK if all operations are OK else USBD_FAIL
@@ -320,10 +315,8 @@ static int8_t CDC_Receive_FS(uint8_t* Buf, uint32_t *Len)
     if (!cdc_connected) {
         osMessagePut(ioEventQueueHandle, CMD_USB_CDC_CONNECT, 0);
     }
-  cdc_receive(Buf, *Len);
-  USBD_CDC_SetRxBuffer(&hUsbDeviceFS, UserRxBufferFS);
-  USBD_CDC_ReceivePacket(&hUsbDeviceFS);
-  return (USBD_OK);
+    cdc_receive(Buf, *Len);
+    return (USBD_OK);
   /* USER CODE END 6 */
 }
 
diff --git a/TNC/UsbPort.cpp b/TNC/UsbPort.cpp
index b3d39a6..f0bcc86 100644
--- a/TNC/UsbPort.cpp
+++ b/TNC/UsbPort.cpp
@@ -13,36 +13,27 @@
 extern "C" void TNC_Error_Handler(int dev, int err);
 
 extern osMessageQId ioEventQueueHandle;
+extern USBD_HandleTypeDef hUsbDeviceFS;
 
 extern "C" void cdc_receive(const uint8_t* buf, uint32_t len)
 {
     using namespace mobilinkd::tnc;
-    if (mobilinkd::tnc::getUsbPort()->queue() != 0)
+
+    // This is running in an interrupt handler.
+
+    UsbCdcRxBuffer_t* usbCdcRxBuffer = (UsbCdcRxBuffer_t*)(buf);
+    usbCdcRxBuffer->size = len;
+
+    if (getUsbPort()->queue() != 0)
     {
-        if (len == 1)
+        // This should always succeed.
+        if (osMessagePut(getUsbPort()->queue(), (uint32_t) buf, 0) == osOK)
         {
-            // Send single byte via queue directly.  Linux seems to do
-            // this for ttyACM ports.
-            osMessagePut(getUsbPort()->queue(), *buf, osWaitForever);
             return;
         }
-
-        auto frame = hdlc::acquire();
-        if (frame)
-        {
-            for (uint32_t i = 0; i != len; ++i)
-            {
-                frame->push_back(*buf++);
-            }
-            frame->source(hdlc::IoFrame::SERIAL_DATA);
-            if (osMessagePut(mobilinkd::tnc::getUsbPort()->queue(),
-                (uint32_t) frame,
-                osWaitForever) != osOK)
-            {
-                mobilinkd::tnc::hdlc::release(frame);
-            }
-        }
     }
+    ERROR("USB packet dropped");
+    USBD_CDC_ReceivePacket(&hUsbDeviceFS); // re-enable receive.
 }
 
 extern "C" void startCDCTask(void const* arg)
@@ -116,7 +107,7 @@ void UsbPort::add_char(uint8_t c)
 
 void UsbPort::run()
 {
-    frame_ = hdlc::acquire();
+    if (frame_ == nullptr) frame_ = hdlc::acquire();
 
     while (true) {
         osEvent evt = osMessageGet(queue(), osWaitForever);
@@ -124,34 +115,31 @@ void UsbPort::run()
             continue;
         }
 
-        uint32_t c = evt.value.v;
+        auto usbCdcRxBuffer = (UsbCdcRxBuffer_t*) evt.value.p;
 
-        if (c < 0x100) // Assume single byte transfer.
-        {
-            add_char(c);
-            continue;
+        // Handle ping-pong buffers.
+        if (usbCdcRxBuffer == usbCdcRxBuffer_1) {
+            USBD_CDC_SetRxBuffer(&hUsbDeviceFS, usbCdcRxBuffer_2->buffer);
+        } else {
+            USBD_CDC_SetRxBuffer(&hUsbDeviceFS, usbCdcRxBuffer_1->buffer);
         }
+        USBD_CDC_ReceivePacket(&hUsbDeviceFS);
 
-        auto input = static_cast<hdlc::IoFrame*>(evt.value.p);
+        INFO("USB p %lu", usbCdcRxBuffer->size);
 
-        if (!isOpen()) {
-            hdlc::release(input);
-            continue;
+        if (isOpen()) {
+            for (uint32_t i = 0; i != usbCdcRxBuffer->size; ++i) {
+                add_char(usbCdcRxBuffer->buffer[i]);
+            }
         }
-
-        for (uint8_t c : *input) {
-            add_char(c);
-        }
-        hdlc::release(input);
     }
-
 }
 
 void UsbPort::init()
 {
     if (cdcTaskHandle_) return;
 
-    osMessageQDef(cdcQueue, 128, void*);
+    osMessageQDef(cdcQueue, 4, void*);
     queue_ = osMessageCreate(osMessageQ(cdcQueue), 0);
 
     osMutexDef(usbMutex);

From 25bc934f0b63a8c3318d0e9387dd87ce0c7d8929 Mon Sep 17 00:00:00 2001
From: Rob Riggs <rob@pangalactic.org>
Date: Sat, 4 Jul 2020 16:43:34 -0500
Subject: [PATCH 36/36] Packets no longer limited to AX.25.

---
 TNC/HdlcDecoder.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/TNC/HdlcDecoder.cpp b/TNC/HdlcDecoder.cpp
index 1ff731a..4191dc2 100644
--- a/TNC/HdlcDecoder.cpp
+++ b/TNC/HdlcDecoder.cpp
@@ -15,7 +15,7 @@ NewDecoder::optional_result_type NewDecoder::operator()(bool input, bool pll_loc
     if (status)
     {
         INFO("HDLC decode status = 0x%02x, bits = %d", int(status), int(report_bits));
-        if (can_pass(status) and packet->size() > 10)
+        if (can_pass(status) and packet->size() > 2)
         {
             result = packet;
             packet = nullptr;