# FreeRTOS Common IO V0.1.2
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import smbus
import argparse

MAX_OUT = int((1.8 / 3.3) * 0xFFF)

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument('d', nargs='?', type=int, default=0, help='dac input')
    args = parser.parse_args()

    data = args.d & 0xFFF

    if data > MAX_OUT:
        data = MAX_OUT

    # I2C channel 1 is connected to the GPIO pins
    channel = 1

    # MCP4725 on adafruit board defaults to address 0x62
    address = 0x62

    # Register addresses (with "normal mode" power-down bits)
    reg_write_dac = 0x40

    bus = smbus.SMBus(channel)

    # 12 bits data is aligned into two bytes with bit 11 as msb i.e. bit 11-4 in the byte 3,
    # bit 3-0 in the byte 4 up four bits.
    lo4 = (data & 0xF) << 4
    hi8 = data >> 4

    bus.write_i2c_block_data(address, reg_write_dac, [hi8, lo4])