def start_adc_difference(self, differential, gain=<NUM_LIT:1>, data_rate=None):
assert <NUM_LIT:0> <= differential <= <NUM_LIT:3>, '<STR_LIT>'<EOL>return self._read(differential, gain, data_rate, ADS1x15_CONFIG_MODE_CONTINUOUS)<EOL>
Start continuous ADC conversions between two ADC channels. Differential
        must be one of:
          - 0 = Channel 0 minus channel 1
          - 1 = Channel 0 minus channel 3
          - 2 = Channel 1 minus channel 3
          - 3 = Channel 2 minus channel 3
        Will return an initial conversion result, then call the get_last_result()
        function continuously to read the most recent conversion result.  Call
        stop_adc() to stop conversions.