Added setGain for LNA Gain (#408)

* Added setGain for LNA Gain

Added setGain for LNA Gain

* Update API.md

Added API for setGain

* Added example to use setGain

Just use setGain after LoRa.begin
// set maximum LNA for better RX sensitivity
// 0: ADC is used and LNA gain is not used.
// 1-6: ADC is not used and LNA gain is used.
LoRa.setGain(6);

* Fixed spacing only

To change tabs to spaces.

* Delete LoRaReceiverCallbackWithLNAGain.ino

To remove as unnecessary.

* To add example for setGain

To add example for setGain as an optional setting.

* Added setGain

To add setGain

* Fixed typo for AGC

Fixed typo for AGC

* Fixed comment for LoRa.setGain(6)

* Make comment for setGain simpler

Make comment for setGain simpler

API.md

@@ -363,6 +363,17 @@ LoRa.enableInvertIQ();
 
 LoRa.disableInvertIQ();
 ```
+### LNA Gain
+
+Set LNA Gain for better RX sensitivity, by default AGC (Automatic Gain Control) is used and LNA gain is not used.
+
+```arduino
+LoRa.setGain(gain);
+```
+
+ * `gain` - LNA gain
+
+Supported values are between `0` and `6`. If gain is 0, AGC will be enabled and LNA gain will not be used. Else if gain is from 1 to 6, AGC will be disabled and LNA gain will be used.
 
 ## Other functions
 

examples/LoRaReceiverCallback/LoRaReceiverCallback.ino

@@ -16,6 +16,9 @@ void setup() {
     while (1);
   }
 
+  // Uncomment the next line to disable the default AGC and set LNA gain, values between 1 - 6 are supported
+  // LoRa.setGain(6);
+  
   // register the receive callback
   LoRa.onReceive(onReceive);
 
@@ -40,4 +43,3 @@ void onReceive(int packetSize) {
   Serial.print("' with RSSI ");
   Serial.println(LoRa.packetRssi());
 }
-

keywords.txt

@@ -47,6 +47,7 @@ enableCrc	KEYWORD2
 disableCrc	KEYWORD2
 enableInvertIQ	KEYWORD2
 disableInvertIQ	KEYWORD2
+setGain	KEYWORD2
 
 random	KEYWORD2
 setPins	KEYWORD2

src/LoRa.cpp

@@ -607,6 +607,32 @@ void LoRaClass::setOCP(uint8_t mA)
   writeRegister(REG_OCP, 0x20 | (0x1F & ocpTrim));
 }
 
+void LoRaClass::setGain(uint8_t gain)
+{
+  // check allowed range
+  if (gain > 6) {
+    gain = 6;
+  }
+  
+  // set to standby
+  idle();
+  
+  // set gain
+  if (gain == 0) {
+    // if gain = 0, enable AGC
+    writeRegister(REG_MODEM_CONFIG_3, 0x04);
+  } else {
+    // disable AGC
+    writeRegister(REG_MODEM_CONFIG_3, 0x00);
+	
+    // clear Gain and set LNA boost
+    writeRegister(REG_LNA, 0x03);
+	
+    // set gain
+    writeRegister(REG_LNA, readRegister(REG_LNA) | (gain << 5));
+  }
+}
+
 byte LoRaClass::random()
 {
   return readRegister(REG_RSSI_WIDEBAND);

src/LoRa.h

@@ -78,6 +78,8 @@ public:
   
   void setOCP(uint8_t mA); // Over Current Protection control
   
+  void setGain(uint8_t gain); // Set LNA gain
+
   // deprecated
   void crc() { enableCrc(); }
   void noCrc() { disableCrc(); }