SeeedStudio Motorshield V2 with STP 42D206 Stepper

I was trying to use a STP42D306 stepper with a SeeedStudio Motor Shield V2 on an Arduino. This is a bipolar 2 phase stepper motor. I needed to modify the code to get it working as the SeeedStudio example is for a Unipolar motor. The code used is below. And here’s a pic of the setup:

image

No guarantee that I’ve done it correctly, but the motor spins clockwise/anticlockwise. There are some nice diagrams of the stepping process here.

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//  Demo function:The application method to drive the stepper motor.
//  Hareware:Stepper motor - 24BYJ48,Seeed's Motor Shield v2.0
//  Author:Frankie.Chu
//  Date:20 November, 2012
#define MOTOR_CLOCKWISE      0
#define MOTOR_ANTICLOCKWISE  1
/******Pins definitions*************/
#define MOTORSHIELD_IN1 8//8
#define MOTORSHIELD_IN2 11//11
#define MOTORSHIELD_IN3 12//12
#define MOTORSHIELD_IN4 13//13
#define CTRLPIN_A   9//9
#define CTRLPIN_B   10//10
 
const unsigned char stepper_ctrl[]={0x27,0x36,0x1e,0x0f};
 
 
 
 
struct MotorStruct
{
  int8_t speed;
  uint8_t direction;
};
MotorStruct stepperMotor;
unsigned int number_of_steps = 200;
/**********************************************************************/
/*Function: Get the stepper motor rotate                               */
/*Parameter:-int steps,the total steps and the direction the motor rotates.*/
/*      if steps > 0,rotates anticlockwise,                 */
/*      if steps < 0,rotates clockwise.                     */
/*Return: void                                          */
void step(int steps)
{
  int steps_left = abs(steps)*4;
  int step_number;
  int millis_delay = 60L * 1000L /number_of_steps/(stepperMotor.speed + 50);
delay(millis_delay);
 
 
  if (steps > 0)
  {
    stepperMotor.direction= MOTOR_ANTICLOCKWISE;
    step_number = 0;
  }
    else if (steps < 0)
  {
    stepperMotor.direction= MOTOR_CLOCKWISE;
    step_number = number_of_steps;
  }
  else return;
 
 
  while(steps_left > 0)
  {
   
               if(step_number%4 == 0) {
                 digitalWrite(MOTORSHIELD_IN1,1);
                 digitalWrite(MOTORSHIELD_IN2,0);
                 digitalWrite(MOTORSHIELD_IN3,0);
                 digitalWrite(MOTORSHIELD_IN4,0);
                 digitalWrite(CTRLPIN_A,1);
                 digitalWrite(CTRLPIN_B,0);                               
               }
               if(step_number%4 == 1) {
                 digitalWrite(MOTORSHIELD_IN1,0);
                 digitalWrite(MOTORSHIELD_IN2,0);
                 digitalWrite(MOTORSHIELD_IN3,1);
                 digitalWrite(MOTORSHIELD_IN4,0);
                 digitalWrite(CTRLPIN_A,0);
                 digitalWrite(CTRLPIN_B,1);                               
               }
               if(step_number%4 == 2) {
                 digitalWrite(MOTORSHIELD_IN1,0);
                 digitalWrite(MOTORSHIELD_IN2,1);
                 digitalWrite(MOTORSHIELD_IN3,0);
                 digitalWrite(MOTORSHIELD_IN4,0);
                 digitalWrite(CTRLPIN_A,1);
                 digitalWrite(CTRLPIN_B,0);                               
               }
               if(step_number%4 == 3) {
                 digitalWrite(MOTORSHIELD_IN1,0);
                 digitalWrite(MOTORSHIELD_IN2,0);
                 digitalWrite(MOTORSHIELD_IN3,0);
                 digitalWrite(MOTORSHIELD_IN4,1);
                 digitalWrite(CTRLPIN_A,0);
                 digitalWrite(CTRLPIN_B,1);                               
               }              
   
    //PORTB = stepper_ctrl[step_number%4];
    delay(millis_delay);
    if(stepperMotor.direction== MOTOR_ANTICLOCKWISE)
    {
      step_number++;
        if (step_number == number_of_steps)
          step_number = 0;
    }
    else
    {
      step_number--;
        if (step_number == 0)
          step_number = number_of_steps;
    }
    steps_left --;
     
  }
}
void initialize()
{
  pinMode(MOTORSHIELD_IN1,OUTPUT);
  pinMode(MOTORSHIELD_IN2,OUTPUT);
  pinMode(MOTORSHIELD_IN3,OUTPUT);
  pinMode(MOTORSHIELD_IN4,OUTPUT);
  pinMode(CTRLPIN_A,OUTPUT);
  pinMode(CTRLPIN_B,OUTPUT);
  stop();
  stepperMotor.speed = 1;
  stepperMotor.direction = MOTOR_CLOCKWISE;
}
/*******************************************/
void stop()
{
  /*Unenble the pin, to stop the motor. */
  digitalWrite(CTRLPIN_A,LOW);
    digitalWrite(CTRLPIN_B,LOW);
}
 
void setup()
{
  initialize();//Initialization for the stepper motor.
}
 
void loop()
{
  step(200);//Stepper motors rotate anticlockwise 200 steps.
  delay(1000);
  step(-200);//Stepper motors rotate clockwise 200 steps.
  delay(1000);
}