keyboard-clicker/KeyboardClicker/KeyboardClicker.ino

/*
  Keyboard Clicker
*/

int outPinsSize = 2;
int outPins[] = { 13, 12 };

int outShift = 0;
int lastCount = 0;

int outBell = 11;

#define RELAY_OFF HIGH
#define RELAY_ON LOW

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);

  for (int i = 0; i < outPinsSize; i++) {
    pinMode(outPins[i], OUTPUT);
    digitalWrite(outPins[i], RELAY_OFF);
  }

  pinMode(outBell, OUTPUT);
  digitalWrite(outBell, RELAY_OFF);
  
  // initialize serial:
  Serial.begin(115200);
}

void loop() {
}

/*
  SerialEvent occurs whenever a new data comes in the hardware serial RX. This
  routine is run between each time loop() runs, so using delay inside loop can
  delay response.
*/
void serialEvent() {
  while (Serial.available()) {
    // get the new byte:
    char inChar = (char)Serial.read();
    //Serial.println(inChar);
    if (inChar >= '0' && inChar <= '9') {
      int count = inChar - '0';
      if (count >= lastCount) {
        outShift = (outShift + 1) % outPinsSize;
      }
      lastCount = count;
      for (int i = 0; i < outPinsSize; i++) {
        digitalWrite(outPins[(i + outShift) % outPinsSize], ((count > i) ? RELAY_ON : RELAY_OFF));
      }
    } else {
      if (inChar == '(') {
        digitalWrite(outBell, RELAY_ON);
        delay(20);
        digitalWrite(outBell, RELAY_OFF);
      }
    }
  }
}