   nh.subscribe(sub); // Start subscribe the "steer_ctrl" topic.
 }
 
-void loop() {
+void loop()
+{
   nh.spinOnce(); // Check topic and if change it, run the call back function.
 }
 

/* Define pulse width time of the stepping motor. */
#define PULSE_WIDTH_MICRO_SECOND 500

enum {
  LEFT,
  RIGHT,
  KEEP
};

enum {
  cw_plus = 3,
  cw_minus,
  ccw_plus,

ros::NodeHandle nh; // The nodeHandle.
ros::Subscriber<geometry_msgs::Twist> sub("steer_ctrl", &steerCb); // Set subscribe the motor_driver topic.

void setup()
{
  /* Set pins Mode. */
  for (int i = cw_plus; i < ccw_minus + 1; i++)
  { // 3: CW+, 4: CW-, 5: CCW+, 6:CCW-
    pinMode(i, OUTPUT);
    digitalWrite(i, LOW); // Default pin status is LOW.
  }
