#include <Arduino.h>
#define LED_PIN 4  

const int freq = 5000;   // PWM frequency in Hz
const int ledChannel = 0; // Use channel 0 (0 to 15 available)
const int resolution = 8; // 8-bit resolution (0-255)

void setup() {
  // Configure the LEDC channel
  ledcSetup(ledChannel, freq, resolution);
  // Attach the LEDC channel to the pin
  ledcAttachPin(LED_PIN, ledChannel);
}

void loop() {
  // Fade in
  for (int dutyCycle = 0; dutyCycle <= 255; dutyCycle++) {
    ledcWrite(ledChannel, dutyCycle);
    delay(5);
  }

  // Fade out
  for (int dutyCycle = 255; dutyCycle >= 0; dutyCycle--) {
    ledcWrite(ledChannel, dutyCycle);
    delay(5);
  }
}