#define LED_PIN 26

const int LEDC_FREQ = 8000;
const int LEDC_RESOLUTION = 12;

int duty = 0;

void setup() {

  ledcAttach(LED_PIN, LEDC_FREQ, LEDC_RESOLUTION);

}

void loop() {

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

  delay(100);
}