int LED1 = 21; // ขา D21
int LED2 = 19; // ขา D19
int LED3 = 18; // ขา D18
int LED4 = 5; // ขา D5
void setup() {
pinMode(LED1, OUTPUT); 
pinMode(LED2, OUTPUT);
pinMode(LED3, OUTPUT);
pinMode(LED4, OUTPUT);
digitalWrite(LED1, LOW);
digitalWrite(LED2, LOW);
digitalWrite(LED3, LOW);
digitalWrite(LED4, LOW);
}
void loop()
{
digitalWrite(LED1, HIGH);
delay(500); 
digitalWrite(LED2, HIGH); 
delay(500);
digitalWrite(LED3, HIGH);
delay(500);
digitalWrite(LED4, HIGH); 
delay(500);
digitalWrite(LED1, LOW);
delay(500);
digitalWrite(LED2, LOW); 
delay(500);
digitalWrite(LED3, LOW); 
delay(500);
digitalWrite(LED4, LOW); 
delay(500);
}