Added RadioLib based carrier detect

config.h

@@ -26,6 +26,7 @@
 #define CFG_LORA_PIN_DIO1     LORA_IRQ  // not used in arduino-LoRa
 #define CFG_LORA_USE_ISR      false // set to true for ISR usage
 #endif
+#define CFG_LORA_USE_CAD      false // set to true to utilize carrier detection
 
 #define CFG_LORA_FREQ         433.775E6
 #define CFG_LORA_BW           125e3

esp32_loraprs.ino

@@ -43,6 +43,7 @@ void initializeConfig(LoraPrs::Config &cfg) {
   cfg.LoraPinDio0 = CFG_LORA_PIN_DIO0;
   cfg.LoraPinDio1 = CFG_LORA_PIN_DIO1; // valid for radiolib only
   cfg.LoraUseIsr = CFG_LORA_USE_ISR;  // set to true for incoming packet ISR usage (stream mode, e.g. speech)
+  cfg.LoraUseCad = CFG_LORA_USE_CAD;  // carrier detect
 
   // aprs configuration
   cfg.AprsHost = "rotate.aprs2.net";

loraprs_config.h

@@ -24,6 +24,7 @@ struct Config
   byte LoraPinDio0;     // lora dio0 pin
   byte LoraPinDio1;     // lora dio1 pin
   bool LoraUseIsr;      // true to use interrupts, false for fallback polling, e.g. if Dio0 is not connected
+  bool LoraUseCad;      // use carrier detect before transmitting
 
   // bluetooth
   String BtName;        // bluetooth device name for the client, set to empty string to disable bluetooth in server mode

loraprs_service.cpp

@@ -225,7 +225,7 @@ void Service::loop()
   if (!isRigToSerialProcessed) {
 
     long currentTime = millis();
-    if (currentTime > csmaSlotTimePrev_ + csmaSlotTime_ && random(0, 255) < csmaP_) {
+    if (!isLoraRxBusy() && currentTime > csmaSlotTimePrev_ + csmaSlotTime_ && random(0, 255) < csmaP_) {
       if (aprsisConn_.available() > 0) {
         onAprsisDataAvailable();
       }
@@ -251,6 +251,14 @@ void Service::loop()
   delay(CfgPollDelayMs);
 }
 
+bool Service::isLoraRxBusy() {
+#ifdef USE_RADIOLIB
+  return cfg_.LoraUseCad && (radio_->getModemStatus() & 0x01); // SX1278_STATUS_SIG_DETECT
+#else
+  return false;
+#endif
+}
+
 #ifdef USE_RADIOLIB
 
 ICACHE_RAM_ATTR void Service::onLoraDataAvailableIsr() {

loraprs_service.h

@@ -39,6 +39,7 @@ private:
   void reconnectWifi() const;
   bool reconnectAprsis();
 
+  bool isLoraRxBusy();
 #ifdef USE_RADIOLIB
   void onLoraDataAvailable();
   static ICACHE_RAM_ATTR void onLoraDataAvailableIsr();