from machine import Pin
import time

# Ultrasonic pins
trig = Pin(12, Pin.OUT)
echo = Pin(13, Pin.IN)

# LEDs
green = Pin(14, Pin.OUT)
yellow = Pin(27, Pin.OUT)
red = Pin(26, Pin.OUT)

def get_distance():
    trig.value(0)
    time.sleep_us(2)
    trig.value(1)
    time.sleep_us(10)
    trig.value(0)

    while echo.value() == 0:
        start = time.ticks_us()
    while echo.value() == 1:
        end = time.ticks_us()

    duration = time.ticks_diff(end, start)
    dist = (duration * 0.0343) / 2  # cm
    return dist

while True:
    distance = get_distance()
    print("Distance:", distance, "cm")

    # Reset LEDs
    green.value(0)
    yellow.value(0)
    red.value(0)

    # Distance zones
    if distance > 50:
        green.value(1)  # Safe
    elif 20 <= distance <= 50:
        yellow.value(1)  # Caution
    else:
        red.value(1)  # Danger

    time.sleep(0.1)