Convert power setting to actual power output.

Author: nseidle

Firmware/LoRaSerial_Firmware/Commands.ino

@@ -607,7 +607,7 @@ void checkCommand()
           reportERROR();
         break;
       case ('7'): //ATS7=
-        if (settingValue >= 0 && settingValue <= 20)
+        if (settingValue >= 14 && settingValue <= 30)
         {
           settings.radioBroadcastPower_dbm = settingValue;
           reportOK();

Firmware/LoRaSerial_Firmware/Radio.ino

@@ -235,9 +235,11 @@ void configureRadio()
   if (radio.setFrequency(channels[0]) == RADIOLIB_ERR_INVALID_FREQUENCY)
     success = false;
 
-  // Set output power (accepted range is -3 - 17 dBm)
-  // NOTE: 20 dBm value allows high power operation, but transmission duty cycle MUST NOT exceed 1%
-  if (radio.setOutputPower(settings.radioBroadcastPower_dbm) == RADIOLIB_ERR_INVALID_OUTPUT_POWER)
+  //The SX1276 and RadioLib accepts a value of 2 to 17, with 20 enabling the power amplifier
+  //Measuring actual power output the radio will output 14dBm (25mW) to 27.9dBm (617mW) in constant transmission
+  //So we use a lookup to convert between the user's chosen power and the radio setting
+  int radioPowerSetting = covertdBmToSetting(settings.radioBroadcastPower_dbm);
+  if (radio.setOutputPower(radioPowerSetting) == RADIOLIB_ERR_INVALID_OUTPUT_POWER)
     success = false;
 
   if (radio.setBandwidth(settings.radioBandwidth) == RADIOLIB_ERR_INVALID_BANDWIDTH)
@@ -822,3 +824,34 @@ bool receiveInProcess()
   //if ((radioStatus & 0b1) == 0) return (false); //If bit 0 is cleared, there is no receive in progress
   //return (true); //If bit 0 is set, forget the other bits, there is a receive in progress
 }
+
+//Convert the user's requested dBm to what the radio should be set to, to hit that power level
+//3 is lowest allowed setting using SX1276+RadioLib
+uint8_t covertdBmToSetting(uint8_t userSetting)
+{
+  if(userSetting < 14) return 3; //Error check
+  
+  switch (userSetting)
+  {
+    case 14: return (2); break;
+    case 15: return (3); break;
+    case 16: return (4); break;
+    case 17: return (5); break;
+    case 18: return (6); break;
+    case 19: return (7); break;
+    case 20: return (7); break;
+    case 21: return (8); break;
+    case 22: return (9); break;
+    case 23: return (10); break;
+    case 24: return (11); break;
+    case 25: return (12); break;
+    case 26: return (13); break;
+    case 27: return (20); break;
+    case 28: return (20); break;
+    case 29: return (20); break;
+    case 30: return (20); break;
+    default: return (3); break;
+  }
+
+
+}

Firmware/LoRaSerial_Firmware/Train.ino

@@ -90,7 +90,7 @@ void moveToTrainingFreq()
   settings.pointToPoint = false;
 
   //Turn power as low as possible. We assume two units will be near each other. 
-  settings.radioBroadcastPower_dbm = 0;
+  settings.radioBroadcastPower_dbm = 14;
 
   generateHopTable(); //Generate frequency table based on current settings
 

Firmware/LoRaSerial_Firmware/settings.h

@@ -131,7 +131,7 @@ typedef struct struct_settings {
   bool encryptData = true; //AES encrypt each packet
   uint8_t encryptionKey[16] = { 0x37, 0x78, 0x21, 0x41, 0xA6, 0x65, 0x73, 0x4E, 0x44, 0x75, 0x67, 0x2A, 0xE6, 0x30, 0x83, 0x08 };
   bool dataScrambling = false; //Use IBM Data Whitening to reduce DC bias
-  uint16_t radioBroadcastPower_dbm = 20; //Max software setting is 20 but radios with built-in PA will get 30dBm(1W) with rx/tx_en pins
+  uint16_t radioBroadcastPower_dbm = 30; //Transmit power in dBm. Max is 30dBm (1W), min is 14dBm (25mW).
   float frequencyMin = 902.0; //MHz
   float frequencyMax = 928.0; //MHz
   uint8_t numberOfChannels = 50; //Divide the min/max freq band into this number of channels and hop between.