Update Adafruit_ADS1x15.py

Adafruit_ADS1x15/Adafruit_ADS1x15.py

@@ -289,7 +289,11 @@ def readADCDifferential(self, chP=0, chN=1, pga=6144, sps=250):
     result = self.i2c.readList(self.__ADS1015_REG_POINTER_CONVERT, 2)
     if (self.ic == self.__IC_ADS1015):
     	# Shift right 4 bits for the 12-bit ADS1015 and convert to mV
-    	return ( ((result[0] << 8) | (result[1] & 0xFF)) >> 4 )*pga/2048.0
+      	val=( ((result[0] << 8) | (result[1] & 0xFF)) >> 4 );
+      	if val > 2047.0:
+	    	return (val - 4096.0)*pga/2048.0
+ 	else: return val*pga/2048.0    
+
     else:
 	# Return a mV value for the ADS1115
 	# (Take signed values into account as well)