[SX127x] Added finishTransmit (#571)

examples/SX127x/SX127x_Transmit_Interrupt/SX127x_Transmit_Interrupt.ino

@@ -114,10 +114,10 @@ void loop() {
 
     }
 
-    // NOTE: in FSK mode, SX127x will not automatically
-    //       turn transmitter off after sending a packet
-    //       set mode to standby to ensure we don't jam others
-    //radio.standby()
+    // clean up after transmission is finished
+    // this will ensure transmitter is disabled,
+    // RF switch is powered down etc.
+    radio.finishTransmit();
 
     // wait a second before transmitting again
     delay(1000);

src/modules/SX127x/SX127x.cpp

@@ -159,7 +159,7 @@ int16_t SX127x::transmit(uint8_t* data, size_t len, uint8_t addr) {
     while(!_mod->digitalRead(_mod->getIrq())) {
       _mod->yield();
       if(_mod->micros() - start > timeout) {
-        clearIRQFlags();
+        finishTransmit();
         return(RADIOLIB_ERR_TX_TIMEOUT);
       }
     }
@@ -177,8 +177,7 @@ int16_t SX127x::transmit(uint8_t* data, size_t len, uint8_t addr) {
     while(!_mod->digitalRead(_mod->getIrq())) {
       _mod->yield();
       if(_mod->micros() - start > timeout) {
-        clearIRQFlags();
-        standby();
+        finishTransmit();
         return(RADIOLIB_ERR_TX_TIMEOUT);
       }
     }
@@ -189,12 +188,8 @@ int16_t SX127x::transmit(uint8_t* data, size_t len, uint8_t addr) {
   // update data rate
   uint32_t elapsed = _mod->micros() - start;
   _dataRate = (len*8.0)/((float)elapsed/1000000.0);
-
-  // clear interrupt flags
-  clearIRQFlags();
-
-  // set mode to standby to disable transmitter
-  return(standby());
+  
+  return(finishTransmit());
 }
 
 int16_t SX127x::receive(uint8_t* data, size_t len) {
@@ -607,6 +602,14 @@ int16_t SX127x::startTransmit(uint8_t* data, size_t len, uint8_t addr) {
   return(RADIOLIB_ERR_NONE);
 }
 
+int16_t SX127x::finishTransmit() {
+  // clear interrupt flags
+  clearIRQFlags();
+
+  // set mode to standby to disable transmitter/RF switch
+  return(standby());
+}
+
 int16_t SX127x::readData(uint8_t* data, size_t len) {
   int16_t modem = getActiveModem();
 

src/modules/SX127x/SX127x.h

@@ -800,6 +800,13 @@ class SX127x: public PhysicalLayer {
     */
     int16_t startTransmit(uint8_t* data, size_t len, uint8_t addr = 0) override;
 
+    /*!
+      \brief Clean up after transmission is done.
+
+      \returns \ref status_codes
+    */
+    int16_t finishTransmit() override;
+
     /*!
       \brief Interrupt-driven receive method. DIO0 will be activated when full valid packet is received.