// the number of the LED pin
const int ledPin = 4;
const int ledPin2 = 15;

// int LED_BUILTIN = 2;    // LED_BUILTIN already preexistent defined

// setting PWM properties
const int freq = 5000;
const int ledChannel = 0;
const int ledChannel2 = 1;
const int resolution = 8;   // equals 0 - 255 increments


void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");

  // Led without PWM
  // pinMode(ledPin, OUTPUT);

  // internal LED
  pinMode(LED_BUILTIN, OUTPUT);

  // PWM: configure LED PWM functionalitites
  ledcSetup(ledChannel, freq, resolution);
  ledcSetup(ledChannel2, freq, resolution);
    // attach the channel to the GPIO to be controlled
  ledcAttachPin(ledPin, ledChannel);
  ledcAttachPin(ledPin2, ledChannel2);
}



void loop() {
  
  /*// put your main code here, to run repeatedly:
  digitalWrite(ledPin, HIGH); // turn the LED on
  delay(500);             // wait for 500 milliseconds
  digitalWrite(ledPin, LOW);  // turn the LED off
  delay(500);
  */

  digitalWrite(LED_BUILTIN, HIGH);
  
  // increase the LED brightness
  for(int dutyCycle = 0; dutyCycle <= 255; dutyCycle += 5){   
    // changing the LED brightness with PWM
    ledcWrite(ledChannel, dutyCycle);
    ledcWrite(ledChannel2, 255-dutyCycle);
    delay(50);
  }

  delay (1000);
  // decrease the LED brightness
  for(int dutyCycle = 255; dutyCycle >= 0; dutyCycle -=5){
    // changing the LED brightness with PWM
    ledcWrite(ledChannel, dutyCycle); 
    ledcWrite(ledChannel2, 255-dutyCycle);  
    delay(50);
  } 

  digitalWrite(LED_BUILTIN, LOW);
  delay (1000);

}