int indicador = 13;
int forward = 12;


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

  pinMode(indicador, OUTPUT);
  pinMode(forward, OUTPUT);
}

void loop() {

  if (Serial.available() > 0) {
    int comando = Serial.read();


    switch (comando) {
     case 'a':
       digitalWrite(13, LOW);
       digitalWrite(12, HIGH);
       Serial.write(comando);
       break;
     case 's':
       digitalWrite(13, HIGH);
       digitalWrite(12, LOW);
       Serial.write(comando);
       break;
     default:
       digitalWrite(13, LOW);
       digitalWrite(12, LOW);
       Serial.write(comando);

    }
  }
 }