true adc

from machine import Pin, ADC
import time, gc

"""
3.14V = 4095 (ATTN_11DB)
"""
def true_adc(v):
    if v < 1 or v > 4095:
        return 0
    return -0.000000000000016 * pow(v, 4) + 0.000000000118171 * pow(v, 3) - 0.000000301211691 * pow(v, 2) + 0.001109019271794 * v + 0.034143524634089

adc = ADC(Pin(34, mode=Pin.IN))
adc.atten(ADC.ATTN_11DB)

while True:
    gc.collect()
    t = time.localtime()
    volt = true_adc(adc.read())
    print("%.2i-%.2i-%.4i %.2i:%.2i:%.2i ==> %.2fV" % (t[2], t[1], t[0], t[3], t[4], t[5], volt))
    time.sleep(1)