debounce

 boolean state = false;

boolean btn_up = true;

void setup()

{

  pinMode(2, INPUT);

  // digitalWrite(3,HIGH);

  pinMode(3, OUTPUT);

  digitalWrite(3, state);

  Serial.begin(9600);

}

void loop()

{

  if (digitalRead(2) == LOW && btn_up == true)

  {

    state = !state;

    digitalWrite(3, state);

    btn_up = false;//你壓下去是false

  }

  else if (digitalRead(2) == HIGH && btn_up == false)//放開 且 btn_false 

  {

    Serial.println("else if");

    Serial.println(btn_up);

    btn_up = true;

    Serial.println(btn_up);

  }

  Serial.println("loop");

  Serial.println(btn_up);

  delay(1000);

}