Do not configure temperature resolution on the MAX31850

Author: karlg100

DallasTemperature.cpp

@@ -288,29 +288,36 @@ bool DallasTemperature::setResolution(const uint8_t* deviceAddress,
 
 		// we can only update the sensor if it is connected
 		if (isConnected(deviceAddress, scratchPad)) {
-			switch (newResolution) {
-			case 12:
-				newValue = TEMP_12_BIT;
-				break;
-			case 11:
-				newValue = TEMP_11_BIT;
-				break;
-			case 10:
-				newValue = TEMP_10_BIT;
-				break;
-			case 9:
-			default:
-				newValue = TEMP_9_BIT;
-				break;
-			}
+			// MAX31850 has no resolution configuration register
+			// this is also a hack as the MAX31850 Coversion time is 100ms max.
+			// use a low res (~10 by spec, but 9 might work) for faster blocking read times.
+			if (deviceAddress[DSROM_FAMILY] == DS1825MODEL && scratchPad[CONFIGURATION] & 0x80 ) {
+				success = true;
+			} else {
+				switch (newResolution) {
+				case 12:
+					newValue = TEMP_12_BIT;
+					break;
+				case 11:
+					newValue = TEMP_11_BIT;
+					break;
+				case 10:
+					newValue = TEMP_10_BIT;
+					break;
+				case 9:
+				default:
+					newValue = TEMP_9_BIT;
+					break;
+				}
 
-			// if it needs to be updated we write the new value
-			if (scratchPad[CONFIGURATION] != newValue) {
-				scratchPad[CONFIGURATION] = newValue;
-				writeScratchPad(deviceAddress, scratchPad);
+				// if it needs to be updated we write the new value
+				if (scratchPad[CONFIGURATION] != newValue) {
+					scratchPad[CONFIGURATION] = newValue;
+					writeScratchPad(deviceAddress, scratchPad);
+				}
+				// done
+				success = true;
 			}
-			// done
-			success = true;
 		}
 	}
 
@@ -347,6 +354,11 @@ uint8_t DallasTemperature::getResolution(const uint8_t* deviceAddress) {
 
 	ScratchPad scratchPad;
 	if (isConnected(deviceAddress, scratchPad)) {
+
+		// MAX31850 has no resolution configuration register
+		if (deviceAddress[DSROM_FAMILY] == DS1825MODEL && scratchPad[CONFIGURATION] & 0x80)
+			return 12;
+
 		switch (scratchPad[CONFIGURATION]) {
 		case TEMP_12_BIT:
 			return 12;