from machine import Pin, time_pulse_us
import time

SOUND_SPEED=340 # sound speed in the air
TRIG_PULSE_DURATION_US=10

trig_pin = Pin(15, Pin.OUT) # Pico GP15 pin
echo_pin = Pin(14, Pin.IN)  # Pico GP14 pin
led_pin = Pin(13, Pin. OUT)

while True:
    # Prepare the signal
    trig_pin.value(0)
    time.sleep_us(5)
    # 10 µs impulse
    trig_pin.value(1)
    time.sleep_us(TRIG_PULSE_DURATION_US)
    trig_pin.value(0)

    ultrason_duration = time_pulse_us(echo_pin, 1, 30000) # Returns the propagation time of the wave. (µs)
    distance_cm = SOUND_SPEED * ultrason_duration / 20000
    if distance_cm <= 200:
        led_pin.value(1)
    else:
        led_pin.value(0)
    print(f"Distance : {distance_cm} cm")
    time.sleep_ms(500)