// Pin assignments
const int ledPin = 9;  // Pin 9 is connected to the LED (PWM)

void setup() {
  // Set pin 9 as an output
  pinMode(ledPin, OUTPUT);
  
  // Call function to set up Timer1
  setupPWM();
}

void loop() {
  // Change the duty cycle (PWM) from 0 to 255
  for (int dutyCycle = 0; dutyCycle <= 255; dutyCycle++) {
    analogWrite(ledPin, dutyCycle);  // Apply PWM signal
    delay(20);  // Small delay to visually notice the brightness change
  }
  
  delay(500);
}

// Function to set up Timer1 for PWM on pin 9
void setupPWM() {
  // Clear Timer1 control registers
  TCCR1A = 0;
  TCCR1B = 0;

  // Set Fast PWM mode with ICR1 as top
  TCCR1A |= (1 << WGM11);
  TCCR1B |= (1 << WGM12) | (1 << WGM13);

  // Set non-inverting mode for PWM on OC1A (pin 9)
  TCCR1A |= (1 << COM1A1);

  // Set ICR1 to define the PWM frequency
  // Example: For 31.25 kHz frequency, ICR1 should be 510
  ICR1 = 510;  // Adjust this value to change the frequency

  // Set prescaler to 1 (no prescaling) for higher frequency
  TCCR1B |= (1 << CS10);

  // Set initial duty cycle to 50% (ICR1 / 2)
  OCR1A = ICR1 / 2;
}