from machine import Pin, ADC, PWM
from time import sleep

# MQ2 Gas Sensor (Analog Read)
mq2_sensor = ADC(26)  # MQ2 connected to GP26 (ADC0)
THRESHOLD = 20000  # Gas threshold value

# Buzzer (PWM for sound)
buzzer = PWM(Pin(15))  # Buzzer connected to GP15
buzzer.freq(2000)  # Set frequency to 2kHz

# Stepper Motor (Exhaust Fan) - Bipolar 4-wire
step_pins = [Pin(16, Pin.OUT), Pin(17, Pin.OUT), Pin(18, Pin.OUT), Pin(19, Pin.OUT)]

# Stepper Motor Sequence (Half Step Mode)
step_sequence = [
    [1, 0, 0, 1],
    [1, 0, 0, 0],
    [1, 1, 0, 0],
    [0, 1, 0, 0],
    [0, 1, 1, 0],
    [0, 0, 1, 0],
    [0, 0, 1, 1],
    [0, 0, 0, 1]
]

def step_motor(direction=1, steps=100):
    """ Function to move the stepper motor """
    for _ in range(steps):
        for step in step_sequence[::direction]:
            for pin, val in zip(step_pins, step):
                pin.value(val)
            sleep(0.002)  # Small delay for smooth movement

def stop_motor():
    """ Function to stop the stepper motor """
    for pin in step_pins:
        pin.value(0)  # Set all motor pins LOW to stop it

# Main loop
while True:
    gas_level = mq2_sensor.read_u16()  # Read gas level (0 - 65535)
    print(f"Gas Level: {gas_level}")  # Debugging

    if gas_level > THRESHOLD:
        print("⚠️ Gas Leak Detected! Turning ON Fan & Alarm!")
        buzzer.duty_u16(30000)  # Activate buzzer
        step_motor(direction=1, steps=200)  # Run fan in forward direction
    else:
        print("✅ Safe Environment! Turning OFF Fan & Alarm!")
        buzzer.duty_u16(0)  # Turn off buzzer
        stop_motor()  # STOP the motor completely

    sleep(1)  # Wait before next reading