const int ledPin = 12;  // GPIO pin for the LED

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

void loop() {
  fadeLed();
}

void fadeLed() {
  int fadeAmount = 25;  // Adjust this value for the desired fade increment/decrement
  int brightness = 0;

  // Fade IN
  while (brightness <= 255) {
    analogWrite(ledPin, brightness);
    brightness += fadeAmount;
    delay(50);  // Adjust this delay for the desired fade speed
  }

  // Fade OUT
  while (brightness >= 0) {
    analogWrite(ledPin, brightness);
    brightness -= fadeAmount;
    delay(50);  // Adjust this delay for the desired fade speed
  }
}