from machine import Pin, Timer
from hcsr04 import HCSR04

ultrasonic = HCSR04(trigger_pin=21, echo_pin=22, echo_timeout_us=1000000)

def timer0_callback(timer):
    print("Distance: {:.2f}cm".format(ultrasonic.distance_cm()))
    
timer0 = Timer(0)
timer0.init(period=500, mode=Timer.PERIODIC, callback=timer0_callback)