void setup() {
  // Serial dialect
  Serial.begin(115200);

  // Status LEDs
  pinMode(3, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(10, OUTPUT);
}

void loop() {
  // Check for input
  check_input();
}

void check_input() {
  if (Serial.available() > 0) {
    if (Serial.read() == '0') {
      // Device unmounted
      // Cut power
      if (cut_power() == 1) {
        // Successful
        light_pin(3);
        delay(1000);
        dark_pin(3);
      } else {
        error();
      }
    } else {
      // Wanting device
      // Give power
      if (give_power() == 1) {
        // Successful
        light_pin(6);
        delay(1000);
        dark_pin(6);
      } else {
        error();
      }      
    }
  }
  // Execution delay
  delay(100);
}

int cut_power() {
  digitalWrite(10, LOW);
  return 1;
}

int give_power() {
  digitalWrite(10, HIGH);
  return 1;
}

void light_pin(int pin) {
  digitalWrite(pin, 100);
}

void dark_pin(int pin) {
  digitalWrite(pin, 0);
}

void error() {
  // Unknown command
  light_pin(5);
  delay(1000);
  dark_pin(5);
}