Ich verwende die Arduino Motor Shield R3

Code:
#define PWM_RECHTS 3
#define BREMSE_LINKS 8
#define BREMSE_RECHTS 9
#define PWM_LINKS 11
#define MOTOR_RECHTS 12
#define MOTOR_LINKS 13

void setup() {
  Serial.begin(9600);
  pinMode(PWM_RECHTS, OUTPUT);
  pinMode(BREMSE_LINKS, OUTPUT);
  pinMode(BREMSE_RECHTS, OUTPUT);
  pinMode(PWM_LINKS, OUTPUT);
  pinMode(MOTOR_RECHTS, OUTPUT);
  pinMode(MOTOR_LINKS, OUTPUT);
}

void loop() {
  while(Serial.available()){
    char getData = Serial.read();
    {
      if (getData == 'w') {
        Vorwaerts();
      }
      else {
        Bremsen();
      }
    }
  }
}


void Vorwaerts() {
  digitalWrite(MOTOR_RECHTS, HIGH);
  digitalWrite(BREMSE_RECHTS, LOW);
  analogWrite(PWM_RECHTS, 255);
  
  digitalWrite(MOTOR_LINKS, HIGH);
  digitalWrite(BREMSE_LINKS, LOW);
  analogWrite(PWM_LINKS, 255);
}

void Bremsen() {
  digitalWrite(BREMSE_RECHTS, HIGH);
  analogWrite(PWM_RECHTS, 0);
  
  digitalWrite(BREMSE_LINKS, HIGH);
  analogWrite(PWM_LINKS, 0);
}