// define LED pin
int ledPin = 4;

//define PWM parameters
const int freq = 5000;
const int ledChannel = 0; 
const int resolution = 8; //resoluion 8bit =256 values

void setup() {
  // This function is used to setup the LEDC channel frequency and resolution.
  ledcSetup(ledChannel, freq, resolution);

  // This function is used to attach the pin to the LEDC channel.
  ledcAttachPin(ledPin, ledChannel);
}

void loop(){
  // increase the LED brightness
  for(int i = 0; i <= 255; i=i+10){   
    // This function is used to set duty for the LEDC channel.
    ledcWrite(ledChannel, i);
    delay(15);
  
  }

  // decrease the LED brightness
  for(int i = 255; i >= 0; i=i-10){
    // changing the LED brightness with PWM
    ledcWrite(ledChannel, i);   
    delay(15);
  
  }
}