// Smoke-Controlled Ventilation Fan using Stepper Motor (A4988)
// Wokwi Compatible – DC fan replaced by Stepper motor

// -------- Pin Definitions --------
int gasPin = A0;        // Gas sensor analog output
int stepPin = 3;       // A4988 STEP pin
int dirPin  = 4;       // A4988 DIR pin
int enablePin = 5;     // A4988 ENABLE pin (optional)

// -------- Gas Thresholds --------
int minGas = 200;      // Clean air
int maxGas = 900;      // Heavy smoke

void setup() {
  pinMode(stepPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
  pinMode(enablePin, OUTPUT);

  digitalWrite(dirPin, HIGH);     // Fixed rotation direction
  digitalWrite(enablePin, LOW);   // Enable driver (LOW = enabled)

  Serial.begin(9600);
}

void loop() {
  int gasValue = analogRead(gasPin);

  // Map gas value to step delay (inverse: more gas = faster motor)
  int stepDelay = map(gasValue, minGas, maxGas, 2000, 200);
  stepDelay = constrain(stepDelay, 200, 2000);

  // Debug
  Serial.print("Gas: ");
  Serial.print(gasValue);
  Serial.print(" | Step Delay (us): ");
  Serial.println(stepDelay);

  // Run stepper motor
  digitalWrite(stepPin, HIGH);
  delayMicroseconds(stepDelay);
  digitalWrite(stepPin, LOW);
  delayMicroseconds(stepDelay);
}