const int ENA = 9;
const int IN1 = 10;
const int IN2 = 11;
void setup() {
  pinMode(ENA, OUTPUT);
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
}

void loop() {
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2,LOW);

  for(int i= 0;i<=255; i++){
    analogWrite(ENA,i);
    delay(10);
  }

  delay(1000);

  digitalWrite(IN1, LOW);
  digitalWrite(IN2, HIGH);

  for(int i=255;i>=0;i++){
    analogWrite(ENA,i);
    delay(10);
  }

  delay(1000);
}