//created by Davood Hakemi with ❤
//arduino toggle led state with interrupt cause by key

#define LED_PIN   13
#define KEY_IT_Pin 2

//define state value as volatile byte
volatile uint8_t state = LOW;

void setup() {

  //initial pins
  pinMode(LED_PIN, OUTPUT);
  pinMode(KEY_IT_Pin, INPUT_PULLUP);

  //initial interrupt key
  attachInterrupt(digitalPinToInterrupt(KEY_IT_Pin), key_pressed, FALLING);
}

void loop() {
  digitalWrite(LED_PIN, state);
}

void key_pressed() {
  state = !state;
}