int ledPin[8]={19,18,5,17,16,4,0,2};
unsigned int previousMillis = 0;
unsigned int currentMillis;
bool ledState=false;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  for(int i=0;i<8;i++)
  {
    pinMode(ledPin[i], OUTPUT);
  }
}

void loop() {
  // put your main code here, to run repeatedly:
  currentMillis=millis();
  if(currentMillis-previousMillis>=1000)
  {
  {
   // Serial.print("previousMillis :");
   // Serial.println(previousMillis);
    //Serial.print("currentMillis :");
    //Serial.println(currentMilliis);
  }
  ledState=!ledState;
  if(ledState)
  {
    for(int i=0;i<8;i++)
    {
      digitalWrite(ledPin[i], HIGH);
    }
  }
  else
  {
    for(int i=0;i<8;i++)
    {
      digitalWrite(ledPin[i], LOW);
    }
  }
  previousMillis=currentMillis;
}
}