Added in an rssi offset for nodes with an LNA such as a heltec v4. Th…

…is will correct the noise floor and recieved rssi values

src/helpers/radiolib/CustomSX1262Wrapper.h

@@ -3,16 +3,22 @@
 #include "CustomSX1262.h"
 #include "RadioLibWrappers.h"
 
+// RSSI_OFFSET is used to compensate for external LNA gain (e.g.Heltec V4)
+// Set to a negative value equal to the LNA gain to get true RSSI values
+#ifndef RSSI_OFFSET
+  #define RSSI_OFFSET 0
+#endif
+
 class CustomSX1262Wrapper : public RadioLibWrapper {
 public:
   CustomSX1262Wrapper(CustomSX1262& radio, mesh::MainBoard& board) : RadioLibWrapper(radio, board) { }
   bool isReceivingPacket() override { 
     return ((CustomSX1262 *)_radio)->isReceiving();
   }
   float getCurrentRSSI() override {
-    return ((CustomSX1262 *)_radio)->getRSSI(false);
+    return ((CustomSX1262 *)_radio)->getRSSI(false) + RSSI_OFFSET;
   }
-  float getLastRSSI() const override { return ((CustomSX1262 *)_radio)->getRSSI(); }
+  float getLastRSSI() const override { return ((CustomSX1262 *)_radio)->getRSSI() + RSSI_OFFSET; }
   float getLastSNR() const override { return ((CustomSX1262 *)_radio)->getSNR(); }
 
   float packetScore(float snr, int packet_len) override {

variants/heltec_v4/platformio.ini

@@ -31,6 +31,7 @@ build_flags =
   -D SX126X_DIO3_TCXO_VOLTAGE=1.8
   -D SX126X_CURRENT_LIMIT=140
   -D SX126X_RX_BOOSTED_GAIN=1
+  -D RSSI_OFFSET=-17       ; GC1109 LNA gain compensation (17dB) - subtract to get true RSSI
   -D PIN_GPS_RX=38
   -D PIN_GPS_TX=39
   -D PIN_GPS_RESET=42