#define led 4
#define btn 2

void readKey();
static char flag = 0;

void setup() {
  pinMode(led, OUTPUT);
  pinMode(btn, INPUT_PULLUP);

  Serial.begin(115200);
}

void loop() {
  readKey();
}

void readKey(){


  if(!digitalRead(btn)){
    flag = 1;
  }

  if(digitalRead(btn) && flag){
    flag = 0;

    digitalWrite(led, !digitalRead(led));

    delay(150);
  }

  Serial.println(flag);


}