[SX126x] Added TRNG support

src/modules/SX126x/SX126x.cpp

@@ -1173,6 +1173,27 @@ int16_t SX126x::autoLDRO() {
   return(ERR_NONE);
 }
 
+uint8_t SX126x::random() {
+  // set mode to Rx
+  setRx(SX126X_RX_TIMEOUT_INF);
+
+  // wait a bit for the RSSI reading to stabilise
+  Module::delay(10);
+
+  // read RSSI value 8 times, always keep just the least significant bit
+  uint8_t randByte = 0x00;
+  for(uint8_t i = 0; i < 8; i++) {
+    uint8_t val = 0x00;
+    readRegister(SX126X_REG_RANDOM_NUMBER_0, &val, sizeof(uint8_t));
+    randByte |= ((val & 0x01) << i);
+  }
+
+  // set mode to standby
+  standby();
+
+  return(randByte);
+}
+
 int16_t SX126x::setTCXO(float voltage, uint32_t delay) {
   // set mode to standby
   standby();

src/modules/SX126x/SX126x.h

@@ -854,7 +854,7 @@ class SX126x: public PhysicalLayer {
 
    /*!
      \brief Forces LoRa low data rate optimization. Only available in LoRa mode. After calling this method, LDRO will always be set to
-     the provided value, regardless of symbol length. To re-enable automatic LDRO configuration, call SX1278::autoLDRO()
+     the provided value, regardless of symbol length. To re-enable automatic LDRO configuration, call SX126x::autoLDRO()
 
      \param enable Force LDRO to be always enabled (true) or disabled (false).
 
@@ -870,6 +870,13 @@ class SX126x: public PhysicalLayer {
    */
    int16_t autoLDRO();
 
+   /*!
+    \brief Get one truly random byte from RSSI noise.
+
+    \returns TRNG byte.
+  */
+   uint8_t random();
+
 #ifndef RADIOLIB_GODMODE
   protected:
 #endif