from machine import Pin, ADC
import time

# =========================================
# GAS DETECTION SYSTEM
# Raspberry Pi Pico + MQ2 + Buzzer + Stepper
# =========================================

# MQ2 analog output -> GP26 (ADC0)
gas_sensor = ADC(26)

# Buzzer -> GP15
buzzer = Pin(15, Pin.OUT)

# Bipolar stepper motor -> GP2, GP3, GP4, GP5
IN1 = Pin(2, Pin.OUT)
IN2 = Pin(3, Pin.OUT)
IN3 = Pin(4, Pin.OUT)
IN4 = Pin(5, Pin.OUT)

# Gas threshold
GAS_THRESHOLD = 30000


# =========================================
# STEPPER MOTOR
# =========================================

sequence = [
    [1, 0, 1, 0],
    [0, 1, 1, 0],
    [0, 1, 0, 1],
    [1, 0, 0, 1]
]


def run_fan():

    for step in sequence:

        IN1.value(step[0])
        IN2.value(step[1])
        IN3.value(step[2])
        IN4.value(step[3])

        time.sleep_ms(5)


def stop_fan():

    IN1.value(0)
    IN2.value(0)
    IN3.value(0)
    IN4.value(0)


# =========================================
# INITIAL STATE
# =========================================

buzzer.value(0)
stop_fan()

print("================================")
print("     GAS DETECTION SYSTEM")
print("================================")
print("System Started")
print()


# =========================================
# MAIN LOOP
# =========================================

while True:

    # Read MQ2 analog value
    gas_value = gas_sensor.read_u16()

    print("Gas Level:", gas_value)

    # GAS ABOVE THRESHOLD
    if gas_value > GAS_THRESHOLD:

        print("WARNING! GAS DETECTED!")
        print("Exhaust Fan: ON")
        print("Alarm: ON")

        # Turn ON buzzer
        buzzer.value(1)

        # Rotate stepper = Exhaust Fan ON
        run_fan()

    # GAS BELOW THRESHOLD
    else:

        print("Gas level normal.")
        print("Exhaust Fan: OFF")
        print("Alarm: OFF")

        # Turn OFF buzzer
        buzzer.value(0)

        # Stop stepper
        stop_fan()

    print("----------------------------")

    time.sleep(1)