Add isChannelActive() function to radio interface

src/mesh/RF95Interface.cpp

@@ -176,6 +176,25 @@ void RF95Interface::startReceive()
     enableInterrupt(isrRxLevel0);
 }
 
+bool RF95Interface::isChannelActive()
+{
+    // check if we can detect a LoRa preamble on the current channel
+    int16_t result;
+    setTransmitEnable(false);
+    setStandby();  // needed for smooth transition
+    result = lora->scanChannel();
+    
+    if (result == PREAMBLE_DETECTED) {
+        // DEBUG_MSG("Channel is busy!\n");
+        return true;
+    }
+
+    assert(result != ERR_WRONG_MODEM);
+    
+    // DEBUG_MSG("Channel is free!\n");
+    return false;
+}
+
 /** Could we send right now (i.e. either not actively receving or transmitting)? */
 bool RF95Interface::isActivelyReceiving()
 {

src/mesh/RF95Interface.h

@@ -40,6 +40,9 @@ class RF95Interface : public RadioLibInterface
      */
     virtual void enableInterrupt(void (*callback)()) { lora->setDio0Action(callback); }
 
+    /** can we detect a LoRa preamble on the current channel? */
+    virtual bool isChannelActive() override;
+
     /** are we actively receiving a packet (only called during receiving state) */
     virtual bool isActivelyReceiving() override;
 

src/mesh/SX126xInterface.cpp

@@ -226,6 +226,23 @@ void SX126xInterface<T>::startReceive()
 #endif
 }
 
+/** Could we send right now (i.e. either not actively receving or transmitting)? */
+template<typename T>
+bool SX126xInterface<T>::isChannelActive()
+{
+    // check if we can detect a LoRa preamble on the current channel
+    int16_t result;
+
+    setStandby(); 
+    result = lora.scanChannel();
+    if (result == PREAMBLE_DETECTED) 
+        return true;
+    
+    assert(result != ERR_WRONG_MODEM);
+    
+    return false;
+}
+
 /** Could we send right now (i.e. either not actively receving or transmitting)? */
 template<typename T>
 bool SX126xInterface<T>::isActivelyReceiving()

src/mesh/SX126xInterface.h

@@ -46,6 +46,9 @@ class SX126xInterface : public RadioLibInterface
      */
     virtual void enableInterrupt(void (*callback)()) { lora.setDio1Action(callback); }
 
+    /** can we detect a LoRa preamble on the current channel? */
+    virtual bool isChannelActive() override;
+
     /** are we actively receiving a packet (only called during receiving state) */
     virtual bool isActivelyReceiving() override;