nix-servo/fast-servo/pyfastservo/loopback.py

import time
from pyfastservo import adc, dac
from pyfastservo.common import (
    ADC_CH1_HIGH_ADDR,
    ADC_CH1_LOW_ADDR,
    CH1_HIGH_WORD_ADDR,
    CH1_LOW_WORD_ADDR,
    read_from_memory,
    write_to_memory
)

def read_adc():
    adc_value = adc.read_adc_channel(ADC_CH1_HIGH_ADDR, ADC_CH1_LOW_ADDR)
    return adc_value

def write_dac(value):
    dac.set_dac_output(value)

def read_dac():
    high_word = read_from_memory(CH1_HIGH_WORD_ADDR, 1)[0]
    low_word = read_from_memory(CH1_LOW_WORD_ADDR, 1)[0]
    return (high_word << 8) | low_word

def perform_loopback_test(test_value):
    print(f"Setting DAC output to {test_value}...")
    write_dac(test_value)
    time.sleep(0.1)  # Allow time for the signal to stabilize

    print("Reading ADC value...")
    adc_value = read_adc()
    print(f"ADC readback: {adc_value}")

    print("Reading DAC value...")
    dac_value = read_dac()
    print(f"DAC readback: {dac_value}")

    if abs(test_value - adc_value) <= 2 and abs(test_value - dac_value) <= 2:
        print("Loopback test PASSED!")
    else:
        print("Loopback test FAILED!")
        print(f"Expected: {test_value}, ADC: {adc_value}, DAC: {dac_value}")

def main():
    test_value = 0x2000  # Mid-range value (8192 in decimal)
    perform_loopback_test(test_value)

if __name__ == "__main__":
    main()