from machine import Pin
import time
print('Hello world')
trig = Pin(17, Pin.OUT)
echo = Pin(16, Pin.IN, Pin.PULL_DOWN)
while True:
     trig.value(0)
     time.sleep(0.1)
     trig.value(1)
     time.sleep_us(2)
     trig.value(0)
     while echo.value()==0:
          pulse_start = time.ticks_us()
     while echo.value()==1:
          pulse_end = time.ticks_us()
     pulse_duration = pulse_end - pulse_start
     distance = pulse_duration * 17165 / 1000000
     distance = round(distance, 0)
     print ('Distance:',distance,'cm')
     time.sleep(1)