Corrected documentation.

BUILD

@@ -1,20 +0,0 @@
-Install required packages:
-  sudo apt-get install git g++ make grep mawk ntp
-
-Make sure you are using the latest kernel by updating your system. The latest
-kernel includes fixes wich improve NTP ppm measurement accuracy:
-  sudo apt-get update
-  sudo apt-get dist-upgrade
-
-Get code/ compile:
-  rm -rf WsprryPi
-  git clone https://github.com/JamesP6000/WsprryPi.git
-  cd WsprryPi
-  make
-
-Install to /usr/local/bin:
-  sudo make install
-
-Uninstall:
-  sudo make uninstall
-

README

@@ -9,18 +9,17 @@ Compatible with the original Raspberry Pi and the Raspberry Pi 2/3.
 ******
 Installation / update:
 ******
-  Make sure you are using the latest kernel by updating your system. The latest
-  kernel includes fixes wich improve NTP ppm measurement accuracy:
-    sudo apt-get update
-    sudo apt-get dist-upgrade
-
   Download and compile code:
     sudo apt-get install git
     git clone https://github.com/JamesP6000/WsprryPi.git
     cd WsprryPi
     make
 
-  See the accompanying BUILD file for more details.
+  Install to /usr/local/bin:
+    sudo make install
+
+  Uninstall:
+    sudo make uninstall
 
 ******
 Usage: (WSPR --help output):
@@ -36,8 +35,10 @@ Usage: (WSPR --help output):
     -p --ppm ppm
       Known PPM correction to 19.2MHz RPi nominal crystal frequency.
     -s --self-calibration
-      Call ntp_adjtime() before every transmission to obtain the PPM error of
-      the crystal.
+      Check NTP before every transmission to obtain the PPM error of the
+      crystal (default setting!).
+    -f --free-running
+      Do not use NTP to correct frequency error of RPi crystal.
     -r --repeat
       Repeatedly, and in order, transmit on all the specified command line
       freqs.
@@ -102,6 +103,11 @@ Radio licensing / RF:
   of isolation, e.g. by using a RF transformer, a simple buffer/driver/PA
   stage, two schottky small signal diodes back to back.
 
+  TAPR makes a very nice shield for the Raspberry Pi that is pre-assembled,
+  performs the appropriate filtering for the 20m band, and also increases
+  the power output to 20dBm! Just connect your antenna and you're good-to-go!
+    https://www.tapr.org/kits_20M-wspr-pi.html
+
 ******
 TX Timing:
 ******
@@ -132,6 +138,10 @@ Calibration:
   Pi has been on for a long time, the crystal's temperature has stabilized,
   and the NTP control loop has converged.
 
+  As of 2017-02, NTP calibration is enabled by default and produces a
+  frequency error of about 0.1 PPM after the Pi has temperature stabilized
+  and the NTP loop has converged.
+
   AM calibration:
   A practical way to calibrate is to tune the transmitter on the same frequency
   of a medium wave AM broadcast station; keep tuning until zero beat (the
@@ -170,7 +180,10 @@ Example usage:
   Using callsign N9NNN, locator EM10, and TX power 33 dBm, transmit a single
   WSPR transmission on the 20m band using NTP based frequency offset
   calibration.
-    sudo ./wspr --self-calibration N9NNN EM10 33 20m
+    sudo ./wspr N9NNN EM10 33 20m
+
+  The same as above, but without NTP calibration:
+    sudo ./wspr --free-running N9NNN EM10 33 20m
 
   Transmit a WSPR transmission slightly off-center on 30m every 10 minutes for
   a total of 7 transmissions, and using a fixed PPM correction value.
@@ -178,7 +191,7 @@ Example usage:
 
   Transmit repeatedly on 40m, use NTP based frequency offset calibration,
   and add a random frequency offset to each transmission to minimize collisions
-  with other transmissions.
+  with other transmitters.
     sudo ./wspr --repeat --offset --self-calibration N9NNN EM10 33 40m
 
 ******
@@ -215,7 +228,8 @@ Credits:
   Michael Tatarinov for adding a patch to get PPM info directly from the
   kernel.
 
-  Retzler András (HA7ILM) added support for the RPi2/3.
+  Retzler András (HA7ILM) for the massive changes that were required to
+  incorporate the mailbox code so that the RPi2 and RPi3 could be supported.
 
   [1] PiFM code from
       http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter

wspr.cpp

@@ -1,5 +1,5 @@
-// WSPR transmitter for the Raspberry Pi. See accompanying README and BUILD
-// files for descriptions on how to use this code.
+// WSPR transmitter for the Raspberry Pi. See accompanying README
+// file for a description on how to use this code.
 
 // License:
 //   This program is free software: you can redistribute it and/or modify
@@ -732,7 +732,7 @@ void print_usage() {
   std::cout << "    for testing only." << std::endl;
   std::cout << std::endl;
   std::cout << "Frequencies can be specified either as an absolute TX carrier frequency, or" << std::endl;
-  std::cout << "using one of the following std::strings. If a std::string is used, the transmission" << std::endl;
+  std::cout << "using one of the following strings. If a string is used, the transmission" << std::endl;
   std::cout << "will happen in the middle of the WSPR region of the selected band." << std::endl;
   std::cout << "  LF LF-15 MF MF-15 160m 160m-15 80m 60m 40m 30m 20m 17m 15m 12m 10m 6m 4m 2m" << std::endl;
   std::cout << "<B>-15 indicates the WSPR-15 region of band <B>." << std::endl;