/*
  5-Second Fade Cycle (2.5s IN, 2.5s OUT)
  Pin 9 must be a PWM pin (marked with ~)
*/

int ledPin = 6;    // LED connected to digital pin 9
int brightness = 0; // Starting brightness

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // --- FADE IN (0 to 255) ---
  // Duration: ~2.5 seconds
  for (int i = 0; i <= 255; i++) {
    analogWrite(ledPin, i);
    delayMicroseconds(9800); // 9.8ms delay * 256 steps ≈ 2508ms
  }

  // --- FADE OUT (255 to 0) ---
  // Duration: ~2.5 seconds
  for (int i = 255; i >= 0; i--) {
    analogWrite(ledPin, i);
    delayMicroseconds(9800); // 9.8ms delay * 256 steps ≈ 2508ms
  }
  
  // Optional: Add a small pause between cycles if desired
  // delay(1000); 
}