void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(2, OUTPUT);
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);

  for (int i = 0; i <10; i++) {
    int k = i%3;
  Serial.print("i รอบที่ :");  Serial.print(i);
   Serial.print("   k :");  Serial.println(k);
   switch (k){
   case 0:
       digitalWrite(2, HIGH);
    delay(500);
     digitalWrite(2, LOW);
    delay(500);
    break;
    case 1:
       digitalWrite(3, HIGH);
    delay(500);
     digitalWrite(3, LOW);
    delay(500);
   break;
    case 2:
       digitalWrite(4, HIGH);
    delay(500);
     digitalWrite(4, LOW);
    delay(500);
   break;
   }
 }

  
}

void loop() {
  // put your main code here, to run repeatedly:

}