/* Arduino USB Keyboard HID Demo
 * Cut/Copy/Paste keys + extra bindings for A, Z, E, R
 */
 
#define KEY_LEFT_CTRL 0x01
#define KEY_LEFT_SHIFT 0x02
 
uint8_t buf[8] = { 0 };  // Keyboard report buffer
 
#define PIN_COPY 5
#define PIN_CUT 6
#define PIN_PASTE 7
#define PIN_A 2
#define PIN_Z 3
#define PIN_E 4
#define PIN_R 5
 
int state = 1;
 
void setup() {
  Serial.begin(9600);
 
  // Initialize pins
  int pins[] = {PIN_COPY, PIN_CUT, PIN_PASTE, PIN_A, PIN_Z, PIN_E, PIN_R};
  for(int i=0; i<7; i++) {
    pinMode(pins[i], INPUT);
    digitalWrite(pins[i], HIGH); // Enable internal pull-ups
  }
 
  delay(200);
}
 
void loop() {
  checkKey(PIN_CUT, 27, KEY_LEFT_CTRL);   // Ctrl+X
  checkKey(PIN_COPY, 6, KEY_LEFT_CTRL);   // Ctrl+C
  checkKey(PIN_PASTE, 25, KEY_LEFT_CTRL); // Ctrl+V
  checkKey(PIN_A, 4);
  checkKey(PIN_Z, 29);
  checkKey(PIN_E, 8);
  checkKey(PIN_R, 21);
}
 
void checkKey(int pin, uint8_t key, uint8_t modifier = 0) {
  if(digitalRead(pin) == LOW) {
    buf[0] = modifier;
    buf[2] = key;
    Serial.write(buf, 8);
    releaseKey();
  }
}
 
void releaseKey() {
  buf[0] = 0;
  buf[2] = 0;
  Serial.write(buf, 8);
  delay(500);
}