Add function for turning low data rate optimize on/off

It's required everywhere where the symbol length exceeds 16 ms

Author: szotsaki

src/LoRa.cpp

@@ -416,6 +416,12 @@ void LoRaClass::setSyncWord(int sw)
   writeRegister(REG_SYNC_WORD, sw);
 }
 
+void LoRaClass::enableLowDataRateOptimize(bool enabled)
+{
+  uint8_t regValue = readRegister(REG_MODEM_CONFIG_3);
+  writeRegister(REG_MODEM_CONFIG_3, bitWrite(regValue, 3, enabled));
+}
+
 void LoRaClass::enableCrc()
 {
   writeRegister(REG_MODEM_CONFIG_2, readRegister(REG_MODEM_CONFIG_2) | 0x04);

src/LoRa.h

@@ -82,6 +82,7 @@ class LoRaClass : public Stream {
   void setCodingRate4(int denominator);
   void setPreambleLength(long length);
   void setSyncWord(int sw);
+  void enableLowDataRateOptimize(bool enabled);
   void enableCrc();
   void disableCrc();