void setup() {

  pinMode(D0, OUTPUT);
  pinMode(D7, OUTPUT);
  pinMode(D6, OUTPUT);
}

void loop() {

  digitalWrite(D0, HIGH);  // turn the LED on (HIGH is the voltage level)
  digitalWrite(D6, HIGH);  // turn the LED on (HIGH is the voltage level)
  digitalWrite(D7, HIGH);  // turn the LED on (HIGH is the voltage level)
  delay(1000);                      // wait for a second
  digitalWrite(D0, LOW);   // turn the LED off by making the voltage LOW
  digitalWrite(D6, LOW);   // turn the LED off by making the voltage LOW
  digitalWrite(D7, LOW);   // turn the LED off by making the voltage LOW
  delay(1000);

}