Collision avoidance.

lib/LoRa/LoRa.cpp

@@ -18,6 +18,7 @@
 #define REG_FIFO_RX_CURRENT_ADDR 0x10
 #define REG_IRQ_FLAGS            0x12
 #define REG_RX_NB_BYTES          0x13
+#define REG_MODEM_STAT           0x18
 #define REG_PKT_SNR_VALUE        0x19
 #define REG_PKT_RSSI_VALUE       0x1a
 #define REG_RSSI_VALUE           0x1b
@@ -251,6 +252,10 @@ float LoRaClass::packetSnr() {
   return ((int8_t)readRegister(REG_PKT_SNR_VALUE)) * 0.25;
 }
 
+bool LoRaClass::rxSignalDetected() {
+  return (readRegister(REG_MODEM_STAT) & 0x01) == 0x01;
+}
+
 long LoRaClass::packetFrequencyError() {
   int32_t freqError = 0;
   freqError         = static_cast<int32_t>(readRegister(REG_FREQ_ERROR_MSB) & B111);

lib/LoRa/LoRa.h

@@ -44,6 +44,7 @@ public:
   int packetRssi();
   float packetSnr();
   long packetFrequencyError();
+  bool rxSignalDetected();
 
   int rssi();
 

src/TaskModem.cpp

@@ -45,6 +45,10 @@ bool ModemTask::loop(System &system) {
   }
 
   if (!_toModem.empty()) {
+    if (_lora_aprs.rxSignalDetected()) {
+      system.getLogger().log(logging::LoggerLevel::LOGGER_LEVEL_DEBUG, getName(), "[%s] RX signal detected. Waiting TX", timeString().c_str());
+      delay(1000);
+    } else {
       std::shared_ptr<APRSMessage> msg = _toModem.getElement();
       if (system.getUserConfig()->lora.tx_enable) {
         system.getLogger().log(logging::LoggerLevel::LOGGER_LEVEL_DEBUG, getName(), "[%s] Transmitting packet '%s'", timeString().c_str(), msg->toString().c_str());
@@ -54,6 +58,7 @@ bool ModemTask::loop(System &system) {
         system.getLogger().log(logging::LoggerLevel::LOGGER_LEVEL_DEBUG, getName(), "[%s] NOT transmitting packet as TX is not enabled '%s'", timeString().c_str(), msg->toString().c_str());
       }
     }
+  }
 
   return true;
 }