const int switchPins[8] = { 2,  3,  4,  5,  6,  7,  8,   9 };
const int powers[8]     = { 1,  2,  4,  8, 16, 32, 64, 128 };
const int enter = 14;

int enterState = 0;
int lastEnterState = 0;

void setup() {
  for (int i = 0; i < 8; i++) {
    pinMode(switchPins[i], INPUT_PULLUP);
  }
  pinMode(enter, INPUT_PULLUP);

  Keyboard.begin();
}


void loop() {
  enterState = digitalRead(enter);

  if (enterState != lastEnterState && enterState == LOW) {
    int keycode = 0;
    for (int i = 0; i < 8; i++) {
      if (digitalRead(switchPins[i]) == LOW) {
        keycode = keycode + powers[i];
      }
    }
    Keyboard.write(keycode);
  }

  lastEnterState = enterState;

  delay(20);
}