char option =' ';
int LED = 12;
void setup() {
  // put your setup code here, to run once:
Serial.end();
Serial.begin(9600);
pinMode(LED, OUTPUT);
delay(500);
Serial.println("*********************************************");
Serial.println("*                    MENU                   *");
Serial.println("*               a = Encender Led            *");
Serial.println("*               b = Apagar Led              *");
Serial.println("* Selecciona una ópcion.a=Encender b=Apagar *");
Serial.println("*********************************************");
}

void loop() {
  // put your main code here, to run repeatedly:
if (Serial.available()> 0)
{
  option = Serial.read();
  if (option =='b')
  {
    digitalWrite(LED, LOW);
  }
  else if (option =='a')
  {
    digitalWrite(LED, HIGH);
  }
}
delay(100);
}