Merge pull request #44 from BiffoBear/Fix_ADC_16_bit_range

Fix ADC 16 bit range

Author: dhalbert

adafruit_mcp3xxx/analog_in.py

@@ -14,7 +14,7 @@
     The ADC chips supported by this library do not use negative numbers. If the resulting
     differential read is less than 0, then the returned integer value (and voltage value) is ``0``.
     If for some reason the voltage on a channel is greater than the reference voltage or
-    less than 0, then the returned integer value is ``65472`` or ``0`` respectively.
+    less than 0, then the returned integer value is ``65535`` or ``0`` respectively.
 
 """
 
@@ -54,15 +54,16 @@ def __init__(
 
     @property
     def value(self) -> int:
-        """Returns the value of an ADC pin as an integer. Due to 10-bit accuracy of the chip, the
-        returned values range [0, 65472]."""
-        return (
-            self._mcp.read(self._pin_setting, is_differential=self.is_differential) << 6
+        """Returns the value of an ADC pin as an integer in the range [0, 65535]."""
+        # Initial result is only 10 bits.
+        result = int(
+            self._mcp.read(self._pin_setting, is_differential=self.is_differential)
         )
+        # Stretch to 16 bits and cover full range.
+        return (result << 6) | (result >> 4)
 
     @property
     def voltage(self) -> float:
         """Returns the voltage from the ADC pin as a floating point value. Due to the 10-bit
-        accuracy of the chip, returned values range from 0 to (``reference_voltage`` *
-        65472 / 65535)"""
-        return (self.value * self._mcp.reference_voltage) / 65535
+        accuracy of the chip, returned values range from 0 to ``reference_voltage``."""
+        return self.value * self._mcp.reference_voltage / 65535