#define TRIG_PIN 12  // Trigger pin
#define ECHO_PIN 13  // Echo pin
#define LED_PIN PB0   // Inbuilt-LED Pin
#define BUTTON_PIN PC13 // Inbuilt Button pin


volatile bool calibrationComplete = false;
float minDistance = 1000;  // Large initial value for calibration
float maxDistance = 0;     // Small initial value for calibration

void setup() {
  Serial.begin(9600);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT);

  // Attach interrupt for the button press
  attachInterrupt(digitalPinToInterrupt(BUTTON_PIN), completeCalibration, FALLING);

  // Set up PWM for LED pin
  analogWriteResolution(8);  // 8-bit resolution (0-255)
}


void loop() {
  if (!calibrationComplete) {
    float distance = measureDistance();

    // Update min/max distances for calibration
    if (distance < minDistance) minDistance = distance;
    if (distance > maxDistance) maxDistance = distance;

    Serial.print("Calibrating... Min: ");
    Serial.print(minDistance);
    Serial.print(" cm, Max: ");
    Serial.println(maxDistance);

    delay(500);  // Slow down calibration readings
  } else {
    // After calibration, use distance to control LED brightness
    float currentDistance = measureDistanceSmooth(10);
    int brightness = map(currentDistance, minDistance, maxDistance, 0, 255);  // Map distance to brightness
    brightness = constrain(brightness, 0, 255);  // Ensure the value stays within 0-255 range

    analogWrite(LED_PIN, brightness);  // Set LED brightness

    Serial.print("Distance(cm):");
    Serial.print(currentDistance);
    Serial.print(",LED Brightness:");
    Serial.println(brightness);

    delay(200);  // Slow down the readings
  }
}

/* Measuring functions*/
float measureDistanceSmooth(int numMeasurements) {
  float totalDistance = 0.0;

  // Take multiple measurements
  for (int i = 0; i < numMeasurements; i++) {
    // Add to the total distance for averaging
    totalDistance += measureDistance();
    delay(5);  // Small delay between measurements
  }

  // return the average distance
  return totalDistance / numMeasurements;
}

float measureDistance() {
  long duration;
  float distance;
  // Clear the trigger pin
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  // Send a 10µs pulse to trigger the sensor
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Measure the time of the echo pulse
  duration = pulseIn(ECHO_PIN, HIGH);

  // Calculate the distance (speed of sound is 34300 cm/s)
  distance = (duration * 0.0343) / 2;
  return distance;
}

// Button interrupt handler to stop calibration
void completeCalibration() {
  calibrationComplete = true;
  Serial.println("Calibration complete.");
}