from machine import Pin,time_pulse_us
from time import sleep,sleep_us

echo = Pin(19, Pin.IN)
trigger = Pin(20, Pin.OUT)

while 1:
    trigger.value(1)
    sleep_us(10)
    trigger.value(0)
    timing=time_pulse_us(echo,1,1000000)
    if timing<0:
        print("error measurement")
    else:
        distance=timing/58
        print("distance",distance,"cm")
    sleep(0.5)