int led1 = 9;
int btn = 13;
int btn_now = 0;
int btn_prev = 1;
int data = 0;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(led1, OUTPUT);
  pinMode(btn, INPUT);
  digitalWrite(btn, HIGH);
}

void loop() {
  // put your main code here, to run repeatedly:
  // kondisi kalo button diteken sekali, lampu nyala terus
  // lampu bakal mati kalo button diteken lagi sekali
  Serial.println(btn_now);

  btn_now = digitalRead(btn);

  if(btn_now == 0 && btn_prev == 1){
    data = !data;
  }

  digitalWrite(led1, data);
  btn_prev = btn_now;
}