from machine import Pin, ADC, time_pulse_us
import time

# PIR sensor pin
pir = Pin(13, Pin.IN)

# Ultrasonic pins
trigger = Pin(5, Pin.OUT)
echo = Pin(18, Pin.IN)

# MQ-2 sensor ADC pin
mq2_adc = ADC(Pin(34))
mq2_adc.atten(ADC.ATTN_11DB)
mq2_adc.width(ADC.WIDTH_12BIT)

# LED pin
led = Pin(2, Pin.OUT)

def measure_distance():
    # Send trigger pulse
    trigger.value(0)
    time.sleep_us(2)
    trigger.value(1)
    time.sleep_us(10)
    trigger.value(0)

    try:
        pulse_time = time_pulse_us(echo, 1, 30000)
    except Exception:
        return None

    if pulse_time < 0:
        return None

    distance_cm = (pulse_time / 2) * 0.0343
    return distance_cm

def read_gas():
    raw = mq2_adc.read()
    return raw

def flash_led():
    led.value(1)
    time.sleep(0.3)
    led.value(0)
    time.sleep(0.3)

while True:
    motion = pir.value()
    dist = measure_distance()
    gas_raw = read_gas()

    print("PIR:", motion, " Distance:", dist, "cm", " Gas:", gas_raw)

    if motion == 1 and dist and dist < 30 and gas_raw > 3000:
        print("⚠️ ALERT: Motion + Close Object + Gas!")
        flash_led()   # blink LED each loop
    else:
        led.value(0)  # keep LED off
        time.sleep(0.5)