void setup() {
  pinMode(2, OUTPUT);
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
}
int time_end=0;
bool toggle =true;
void loop() {
  if(millis() - time_end >= 1000)
  {
    time_end = millis();
    digitalWrite(2,toggle);
    toggle = !toggle;
  }
  delay(10); // this speeds up the simulation
}