def read_adc_difference(self, differential):
        """Read the difference between two channels.  Differential should be a
        value of:
          - 0: Return channel 0 minus channel 1
          - 1: Return channel 1 minus channel 0
          - 2: Return channel 2 minus channel 3
          - 3: Return channel 3 minus channel 2
          - 4: Return channel 4 minus channel 5
          - 5: Return channel 5 minus channel 4
          - 6: Return channel 6 minus channel 7
          - 7: Return channel 7 minus channel 6
        """
        assert 0 <= differential <= 7, 'Differential number must be a value of 0-7!'
        # Build a difference channel read command.
        command = 0b10 << 6                  # Start bit, differential read
        command |= (differential & 0x07) << 3  # Channel number (in 3 bits)
        # Note the bottom 3 bits of command are 0, this is to account for the
        # extra clock to do the conversion, and the low null bit returned at
        # the start of the response.
        resp = self._spi.transfer([command, 0x0, 0x0])
        # Parse out the 10 bits of response data and return it.
        result = (resp[0] & 0x01) << 9
        result |= (resp[1] & 0xFF) << 1
        result |= (resp[2] & 0x80) >> 7
        return result & 0x3FF
Read the difference between two channels.  Differential should be a
        value of:
          - 0: Return channel 0 minus channel 1
          - 1: Return channel 1 minus channel 0
          - 2: Return channel 2 minus channel 3
          - 3: Return channel 3 minus channel 2
          - 4: Return channel 4 minus channel 5
          - 5: Return channel 5 minus channel 4
          - 6: Return channel 6 minus channel 7
          - 7: Return channel 7 minus channel 6