from machine import Pin, time_pulse_us
import time

# ----- Ultrasonic Sensor Pins -----
TRIG = [Pin(2, Pin.OUT), Pin(4, Pin.OUT), Pin(6, Pin.OUT), Pin(8, Pin.OUT)]
ECHO = [Pin(3, Pin.IN), Pin(5, Pin.IN), Pin(7, Pin.IN), Pin(9, Pin.IN)]

# ----- LEDs for each slot -----
LED = [Pin(10, Pin.OUT), Pin(11, Pin.OUT), Pin(12, Pin.OUT), Pin(13, Pin.OUT)]

# ----- Buzzer -----
BUZZER = Pin(15, Pin.OUT)

# ----- Threshold for slot detection (cm) -----
THRESHOLD = 10

# ----- Measure distance function -----
def measure_distance(trig, echo):
    trig.low()
    time.sleep_us(2)
    trig.high()
    time.sleep_us(10)
    trig.low()
    duration = time_pulse_us(echo, 1, 30000)  # max 30ms
    if duration < 0:
        return -1
    distance = (duration / 2) / 29.1
    return distance

# ----- Main Loop -----
while True:
    slot_status = []
    for i in range(4):
        dist = measure_distance(TRIG[i], ECHO[i])
        if dist != -1 and dist < THRESHOLD:
            slot_status.append("Occupied")
            LED[i].on()      # LED ON if occupied
        else:
            slot_status.append("Free")
            LED[i].off()     # LED OFF if free
    
    # Print slot status to serial monitor
    print("---- Parking Status ----")
    for i in range(4):
        print(f"Slot {i+1}: {slot_status[i]}")
    
    # Buzzer alert if all slots full
    if slot_status.count("Occupied") == 4:
        print("Parking Full! Buzzer ON")
        BUZZER.high()
    else:
        BUZZER.low()
    
    print("------------------------\n")
    time.sleep(1)