Simple dustsensor MicroPython library

dustsensor.py

import machine
import time

# Python version of
# https://www.arduino.cc/reference/en/language/functions/advanced-io/pulsein/
# returns duration in MICRO seconds
def pulseIn(pin, value):
    # Wait till we hit the wanted value
    while pin.value() != value:
        pass
    # Start timing
    start = time.ticks_us()
    # Wait till we are no longer == value
    while pin.value() == value:
        pass
    now = time.ticks_us()
    tdiff = time.ticks_diff(now, start)
    return tdiff

def readDustsensor(pin, sampletime_ms):
    starttime_ms = time.ticks_ms()
    timePassed = 0
    lowpulseoccupancy_us = 0
    while timePassed < sampletime_ms:
        duration_us = pulseIn(pin, 0)
        lowpulseoccupancy_us = lowpulseoccupancy_us+duration_us
        timePassed = time.ticks_diff(time.ticks_ms(), starttime_ms)

    # Integer percentage 0%-100%
    ratio = lowpulseoccupancy_us/(timePassed*10.0)
    # Using spec sheet curve
    concentration = 1.1*pow(ratio, 3)-3.8*pow(ratio, 2)+520*ratio+0.62

    return concentration