Simple H-Bridge Control.ino

const int ENABLE_A = 4;
const int ENABLE_B = 5;
const int SPEED = 6;

void setup() {
  pinMode(ENABLE_A, OUTPUT);
  pinMode(ENABLE_B, OUTPUT);
  pinMode(SPEED, OUTPUT);
}

void brakeMotor(int milliseconds) {
  digitalWrite(ENABLE_A, LOW);
  digitalWrite(ENABLE_B, LOW);
  analogWrite(SPEED, 0);
  delay(milliseconds);
}

void runMotor(int speed, int milliseconds, int isA = true) {
  if (isA) {
    digitalWrite(ENABLE_A, HIGH);
    digitalWrite(ENABLE_B, LOW);
  } else {
    digitalWrite(ENABLE_A, LOW);
    digitalWrite(ENABLE_B, HIGH);
  }
  analogWrite(SPEED, speed);
  delay(milliseconds);
}

void loop() {
  runMotor(255, 100, true);
  brakeMotor(100);
  runMotor(255, 100, false);
  brakeMotor(100);
}