from machine import Pin
import time

# ---------- Pin Configuration (matches diagram.json) ----------
gas_do   = Pin(16, Pin.IN)          # MQ2 digital output -> GP16
buzzer   = Pin(15, Pin.OUT)         # Buzzer -> GP15

step_pin   = Pin(14, Pin.OUT)       # A4988 STEP -> GP14
dir_pin    = Pin(13, Pin.OUT)       # A4988 DIR  -> GP13
enable_pin = Pin(12, Pin.OUT)       # A4988 ENABLE -> GP12 (active LOW)

# ---------- Initial state ----------
enable_pin.value(1)   # 1 = disabled (A4988 ENABLE is active-LOW)
dir_pin.value(1)      # fixed rotation direction
buzzer.value(0)

def motor_enable():
    enable_pin.value(0)   # LOW = driver enabled, coils energized

def motor_disable():
    enable_pin.value(1)   # HIGH = driver disabled, coils off (saves power)

def step_once(delay_us=800):
    step_pin.value(1)
    time.sleep_us(delay_us)
    step_pin.value(0)
    time.sleep_us(delay_us)

# ---------- Main Loop ----------
print("Gas Detection System Started")

while True:
    gas_detected = gas_do.value()   # 1 = gas above threshold, 0 = normal
    # NOTE: if your buzzer/motor react backwards when you test in Wokwi,
    # this polarity is inverted on some sensor builds -- just flip the
    # condition below to "if gas_detected == 0:" instead.

    if gas_detected == 1:
        print("!! Gas level HIGH - Activating exhaust fan and alarm !!")
        buzzer.value(1)
        motor_enable()
        for _ in range(20):         # spin stepper while gas stays high
            step_once()
    else:
        print("Gas level normal - System OFF")
        buzzer.value(0)
        motor_disable()
        time.sleep_ms(100)