from machine import Pin, PWM, ADC
import utime

mq2 = ADC(Pin(26))

buzzer = PWM(Pin(14))  
buzzer.freq(1000)  

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],  
    [0, 1, 1, 0],  
    [0, 1, 0, 1],  
    [1, 0, 0, 1],  
]

# Gas Threshold
THRESHOLD = 20000  

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)

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)  # ON 
    utime.sleep_ms(duration)  
    buzzer.duty_u16(0)  # OFF 

while True:
    gas_level = mq2.read_u16() 
    print(f"Gas Level: {gas_level}")  

    if gas_level > THRESHOLD:
        print("Gas detected! Activating alarm and exhaust fan.")
        buzzer_beep(1000)  
        stepper_rotate(256, 2)  
    else:
        print("Gas level normal.")
        buzzer.duty_u16(0)  
        stepper_stop()  

    utime.sleep(1)