from machine import Pin, ADC, PWM
import time

# Configure the MQ2 gas sensor
mq2_sensor = ADC(26)  # Connect MQ2 analog output to GPIO 26 (ADC0)

# Configure the buzzer
buzzer = PWM(Pin(15))  # Connect buzzer to GPIO 15
buzzer.freq(440)  # Set frequency to 440 Hz (A4 note)
buzzer.duty_u16(0)  # Initially off

# Configure stepper motor pins (for a standard 4-pin bipolar stepper)
in1 = Pin(16, Pin.OUT)
in2 = Pin(17, Pin.OUT)
in3 = Pin(18, Pin.OUT)
in4 = Pin(19, Pin.OUT)

# Stepper motor sequence (full step sequence)
step_sequence = [
    [1, 0, 0, 0],
    [0, 1, 0, 0],
    [0, 0, 1, 0],
    [0, 0, 0, 1]
]

# Define LED pin for status indication
status_led = Pin(25, Pin.OUT)  # Built-in LED on Pi Pico

# Set the gas threshold level (adjust this value based on your sensor calibration)
# MQ2 sensor returns values from 0-65535 (16-bit ADC)
GAS_THRESHOLD = 27000  # This is an example threshold, needs calibration

# Variables to track system state
fan_running = False

def set_stepper_step(step):
    """Set the stepper motor pins according to the sequence step"""
    in1.value(step_sequence[step][0])
    in2.value(step_sequence[step][1])
    in3.value(step_sequence[step][2])
    in4.value(step_sequence[step][3])

def stepper_stop():
    """Turn off all stepper motor pins to stop it and save power"""
    in1.value(0)
    in2.value(0)
    in3.value(0)
    in4.value(0)

def start_fan():
    """Start the stepper motor as an exhaust fan"""
    global fan_running
    fan_running = True
    print("Starting exhaust fan")

def stop_fan():
    """Stop the stepper motor"""
    global fan_running
    fan_running = False
    stepper_stop()
    print("Stopping exhaust fan")

def start_alarm():
    """Turn on the buzzer alarm"""
    buzzer.duty_u16(32768)  # 50% duty cycle
    print("Alarm ON")

def stop_alarm():
    """Turn off the buzzer alarm"""
    buzzer.duty_u16(0)  # 0% duty cycle
    print("Alarm OFF")

def read_gas_level():
    """Read the gas level from MQ2 sensor"""
    # Read raw analog value (0-65535)
    raw_value = mq2_sensor.read_u16()
    print(f"Gas level: {raw_value}")
    return raw_value

print("Gas Detection System Starting...")
print(f"Gas threshold set to: {GAS_THRESHOLD}")

try:
    step_count = 0
    while True:
        # Read the current gas level
        gas_level = read_gas_level()
        
        # Check if gas level is above threshold
        if gas_level > GAS_THRESHOLD:
            # Gas level is high, activate alarm and fan
            status_led.value(1)  # Turn on status LED
            
            if not fan_running:
                start_fan()
                start_alarm()
            
            # Only run the stepper if fan should be running
            if fan_running:
                # Move stepper motor one step
                set_stepper_step(step_count % 4)
                step_count += 1
                
        else:
            # Gas level is normal, deactivate alarm and fan
            status_led.value(0)  # Turn off status LED
            
            if fan_running:
                stop_fan()
                stop_alarm()
        
        # Short delay
        time.sleep(1)
        
except KeyboardInterrupt:
    # Clean shutdown
    stepper_stop()
    stop_alarm()
    print("System stopped")