Add retry for getTempC.

I have only implemented this for getTempC because that's the method I use in project (i.e. not getTempF).

Author: mitchyboy9

DallasTemperature.cpp

@@ -723,22 +723,27 @@ int32_t DallasTemperature::calculateTemperature(const uint8_t* deviceAddress,
 // the numeric value of DEVICE_DISCONNECTED_RAW is defined in
 // DallasTemperature.h. It is a large negative number outside the
 // operating range of the device
-int32_t DallasTemperature::getTemp(const uint8_t* deviceAddress) {
+int32_t DallasTemperature::getTemp(const uint8_t* deviceAddress, byte retryCount = 0) {
 
 	ScratchPad scratchPad;
-	if (isConnected(deviceAddress, scratchPad))
-		return calculateTemperature(deviceAddress, scratchPad);
-	return DEVICE_DISCONNECTED_RAW;
-
+	
+	byte retries = 0;
+	
+	while (retries++ <= retryCount) {
+    if (isConnected(deviceAddress, scratchPad))
+      return calculateTemperature(deviceAddress, scratchPad);
+  	}
+  
+  	return DEVICE_DISCONNECTED_RAW;
 }
 
 // returns temperature in degrees C or DEVICE_DISCONNECTED_C if the
 // device's scratch pad cannot be read successfully.
 // the numeric value of DEVICE_DISCONNECTED_C is defined in
 // DallasTemperature.h. It is a large negative number outside the
 // operating range of the device
-float DallasTemperature::getTempC(const uint8_t* deviceAddress) {
-	return rawToCelsius(getTemp(deviceAddress));
+float DallasTemperature::getTempC(const uint8_t* deviceAddress, byte retryCount = 0) {
+	return rawToCelsius(getTemp(deviceAddress, retryCount));
 }
 
 // returns temperature in degrees F or DEVICE_DISCONNECTED_F if the

DallasTemperature.h

@@ -159,10 +159,10 @@ class DallasTemperature {
 	request_t requestTemperaturesByIndex(uint8_t);
 
 	// returns temperature raw value (12 bit integer of 1/128 degrees C)
-	int32_t getTemp(const uint8_t*);
+	int32_t getTemp(const uint8_t*, byte retryCount = 0);
 
 	// returns temperature in degrees C
-	float getTempC(const uint8_t*);
+	float getTempC(const uint8_t*, byte retryCount = 0);
 
 	// returns temperature in degrees F
 	float getTempF(const uint8_t*);