serial_led.ino

int loop_cnt =0;

void setup() {
  // put your setup code here, to run once:
  pinMode(13, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(10, OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
//  digitalWrite(13, HIGH);
//  digitalWrite(12, HIGH);
//  digitalWrite(11, HIGH);
//  digitalWrite(10, HIGH);
  int delay_speed = 100;

  if (loop_cnt %3 ==0) {
    delay_speed = 1000;
    loop_cnt = 0;
  }
  
  for( int i=13; i>=10; --i) {
    digitalWrite(i, HIGH);
    delay(delay_speed); 
  }
  delay(1000);

  for( int j=10; j<=13; ++j) {
    digitalWrite(j, LOW);
    delay(delay_speed); 
  }
  loop_cnt++;
  
}