from machine import Pin, time_pulse_us
import utime

trig_pin = Pin(17, Pin.OUT)
echo_pin = Pin(16, Pin.IN)

SOUND_SPEED = 343.2 # speed of sound 343.2 m/s

def ultraSonic():
    # send a pulse for 10 millisecnods
    trig_pin.high()
    utime.sleep_ms(10)
    trig_pin.low()
    
    # calculate time to for pulse return
    duration = time_pulse_us(echo_pin, 1)
    
    # multiply duration by speed of sound, 
    # convert to cm, round to 1 decimal place
    distance = round((SOUND_SPEED * duration / 20000), 1)
    
    return distance


while True:
    # get sensor reading
    us_reading = ultraSonic()
    print(f"Distance in cm: {us_reading}")
    # take reading every second
    utime.sleep(1)