from machine import Pin
import time

# 1. Setup the Hardware Pins
trigger = Pin(3, Pin.OUT)
echo = Pin(2, Pin.IN)
warning_led = Pin(15, Pin.OUT)

def measure_distance():
    # Send a quick 10-microsecond sound pulse from the sensor
    trigger.low()
    time.sleep_us(2)
    trigger.high()
    time.sleep_us(10)
    trigger.low()
    
    # Start a stopwatch when the sound wave leaves
    while echo.value() == 0:
        signaloff = time.ticks_us()
        
    # Stop the stopwatch when the sound wave bounces back
    while echo.value() == 1:
        signalon = time.ticks_us()
        
    # Calculate how much time passed in microseconds
    timepassed = signalon - signaloff
    
    # Convert time to distance (Speed of sound is ~0.0343 cm/microsecond)
    # Divide by 2 because the sound traveled to the object AND back
    distance_cm = (timepassed * 0.0343) / 2
    return distance_cm

print("Starting Parking Assist System...")

# 2. The Main Loop (This runs forever while the board has power)
while True:
    dist = measure_distance()
    print("Distance to object:", round(dist, 1), "cm")
    
    # 3. The Logic: Turn on the LED if an object is closer than 100cm
    if dist < 100:
        warning_led.value(1)
    else:
        warning_led.value(0)
        
    # Wait half a second before checking the distance again
    time.sleep(0.5)