#define LED_PIN 26

const int ledChannel = 0;
const int frequency = 8000;
const int resolution = 12;

int duty = 0;

void setup() {
  ledcSetup(ledChannel, frequency, resolution);
  ledcAttachPin(LED_PIN, ledChannel);
}

void loop() {

  if (duty <= 4095) {
    ledcWrite(ledChannel, duty);
    duty += 100;
  } else {
    ledcWrite(ledChannel, duty);
    duty = 0;
  }

  delay(100);
}