Get Voltage from BrickPi+

get_voltage.py

import smbus

def get_voltage():
    """
    Reads the digital output code of the MCP3021 chip on the BrickPi+ over i2c.
    Some bit operation magic to get a voltage floating number.

    If this doesnt work try this on the command line: i2cdetect -y 1
    The 1 in there is the bus number, same as in bus = smbus.SMBus(1)
    Google the resulting error.

    :return: voltage (float)
    """
    try:
            bus = smbus.SMBus(1)            # SMBUS 1 because we're using greater than V1.
            address = 0x48
            # time.sleep(0.1) #Is this necessary?
    
            # read data from i2c bus. the 0 command is mandatory for the protocol but not used in this chip.
            data = bus.read_word_data(address, 0)

            # from this data we need the last 4 bits and the first 6.
            last_4 = data & 0b1111 # using a bit mask
            first_6 = data >> 10 # right shift 10 because data is 16 bits

            # together they make the voltage conversion ratio
            # to make it all easier the last_4 bits are most significant :S
            vratio = (last_4 << 6) | first_6

            # Now we can calculate the battery voltage like so:
            ratio = 0.0179     # This is an empyrical value based on several different batteries
            voltage = vratio * ratio

            return voltage

    except:
            return 0.0
            
if __name__ == "__main__":
    print get_voltage()