from machine import Pin, ADC, PWM
import time

# ---------- GAS SENSOR ----------
gas_sensor = ADC(26)

# ---------- BUZZER ----------
buzzer = PWM(Pin(15))   
# ---------- STEPPER MOTOR ----------
A_plus  = Pin(2, Pin.OUT)
A_minus = Pin(3, Pin.OUT)
B_plus  = Pin(4, Pin.OUT)
B_minus = Pin(5, Pin.OUT)

# Gas threshold
threshold = 30000

sequence = [
    (1,0,1,0),
    (0,1,1,0),
    (0,1,0,1),
    (1,0,0,1)
]

def rotate_motor():
    for step in sequence:
        A_plus.value(step[0])
        A_minus.value(step[1])
        B_plus.value(step[2])
        B_minus.value(step[3])
        time.sleep(0.003)

def stop_motor():
    A_plus.value(0)
    A_minus.value(0)
    B_plus.value(0)
    B_minus.value(0)

# ---------- MAIN LOOP ----------
while True:

    gas_value = gas_sensor.read_u16()
    print("Gas Level:", gas_value)

    if gas_value > threshold:
        print("Gas Detected!")
        buzzer.freq(1000)        # sound frequency
        buzzer.duty_u16(30000)   # continuous sound
        rotate_motor()           # fan ON

    else:
        print("Gas Normal")
        buzzer.duty_u16(0)       # buzzer OFF
        stop_motor()             # fan OFF

    time.sleep(0.1)