#define LED1 17
#define LED2 18
#define LED3 19

int val;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  ledcSetup(0, 1000, 8);

  ledcAttachPin(LED1, 0);
  ledcAttachPin(LED2, 0);
  ledcAttachPin(LED3, 0);

}

void loop() {
  // put your main code here, to run repeatedly:
  for(val=0; val<255; val++) {
    ledcWrite(0, val);
    Serial.println(val);
    delay(10);
  }
  for(val=255; val>0; val--) {
    ledcWrite(0, val);
    Serial.println(val);
    delay(10);
  }
   // this speeds up the simulation
}