from machine import Pin, PWM, ADC
import utime

# Define MQ-2 Gas Sensor
mq2 = ADC(Pin(26))

# Define Passive Buzzer (Use PWM)
buzzer = PWM(Pin(14))
buzzer.freq(1000)  # Set frequency to 1 kHz
buzzer.duty_u16(0)  # Ensure buzzer is off initially

# Define Stepper Motor Pins (Bipolar Stepper Motor)
stepper_pins = [Pin(16, Pin.OUT), Pin(17, Pin.OUT), Pin(18, Pin.OUT), Pin(19, Pin.OUT)]

# Step sequence for Bipolar Stepper Motor
stepper_seq = [
    [1, 0, 1, 0],  # Step 1
    [0, 1, 1, 0],  # Step 2
    [0, 1, 0, 1],  # Step 3
    [1, 0, 0, 1],  # Step 4
]

# Gas Threshold
THRESHOLD = 20000  # Adjust based on sensor calibration

def stepper_rotate(steps=256, delay=2):
    """Rotates stepper motor in forward direction"""
    for _ in range(steps):
        for step in stepper_seq:
            for pin, val in zip(stepper_pins, step):
                pin.value(val)
            utime.sleep_ms(delay)
    stepper_stop()  # Stop motor after rotation

def stepper_stop():
    """Stops the stepper motor"""
    for pin in stepper_pins:
        pin.value(0)

def buzzer_beep(duration=1000):
    """Beeps buzzer for a given duration (supports active & passive buzzers)"""
    buzzer.duty_u16(30000)  # Turn ON buzzer
    utime.sleep_ms(duration)
    buzzer.duty_u16(0)  # Turn OFF buzzer

while True:
    gas_level = mq2.read_u16()  # Read gas sensor value
    print(f"Gas Level: {gas_level}")  # Debug output

    if gas_level > THRESHOLD:
        print("Gas detected! Activating alarm and exhaust fan.")
        buzzer_beep(1000)  # Buzzer beeps for 1 second
        stepper_rotate(256, 2)  # Move stepper motor
    else:
        print("Gas level normal.")
        stepper_stop()  # Stop stepper motor if no gas detected

    utime.sleep(1)