Arduino L298 stepper motor driver

Here is an example Arduino sketch to drive a stepper motor using the L298 chip. The actual driver is the "StepperL298N" class, and then there is some code to test it. When you instantiate the class, pass in the 4 Arduino pins that you have connected to the stepper motor. For example, "StepperL298N motor(4,5,6,7)" will drive a motor connected to Arduino pins 4,5,6,7. If you need to drive 2 motors, just create 2 instances of the class with different pins!

To move the motor 1 tick, call the step(bool direction) member function. Call it with 1 to go forward, and 0 to go backwards. The faster you call it, the faster the motor will go. Note that the Arduino can easily call step() much faster than the motor can possibly be driven, so you must insert a delay by calling the delay function. For my test motor (and old AMP 2.3 volt 60oz*in, which I got from taking apart a printer) you have to delay at least 5ms for the motor to work.

/*
 * stepperL298N
 * Copyright 2008 G. Andrew Stone
 * Licensed under the Common Public License V1.0
 * For the full text of this license see: http://www.opensource.org/licenses/cpl1.0.php
 *
 */

int ledPin = 13;

void setup()                    // run once, when the sketch starts
{
  pinMode(ledPin, OUTPUT);      // sets the digital pin as output
}

void mydelay(int clk)
{
  int i;
  for (i=0;i< clk;i++);
  //delay(clk);
}

class StepperL298N
{
  public:
  byte pins[4];
  byte curState;
  byte* lut;
  StepperL298N(byte pin1,byte pin2,byte pin3,byte pin4);
     
  void step(boolean dir);
  void halfStep(boolean yes) { if (yes) lut = halfStepLut; else lut = fullStepLut;}
  void start() { curState = 0xa;}
  void free() { curState = 0; }
  void brake() { curState = 0; }

  byte fullStepLut[16];
  byte halfStepLut[16];
};


StepperL298N::StepperL298N(byte pin1,byte pin2,byte pin3,byte pin4)
{
  pins[0] = pin1; pins[1] = pin2; pins[2]=pin3; pins[3] = pin4;
  lut = fullStepLut;
  for (int i=0;i<4;i++)
    {
    pinMode(pins[i], OUTPUT);      // sets the digital pin as output
    }

 memset(&fullStepLut,sizeof(byte)*16,0);
 memset(&halfStepLut,sizeof(byte)*16,0);

 // High nibble goes one way, low the other
 fullStepLut[0] = 0;
 // 1010 -> 1001 -> 0101 -> 0110
 fullStepLut[0xa] = 0x9 | 0x60;
 fullStepLut[0x9] = 0x5 | 0xa0;
 fullStepLut[0x5] = 0x6 | 0x90;
 fullStepLut[0x6] = 0xa | 0x50;

 halfStepLut[0] = 0;
 // 1010 -> 1000 -> 1001 -> 0001 -> 0101 -> 0100 -> 0110 -> 0010
 halfStepLut[0xa] = 0x8 | 0x20;
 halfStepLut[0x8] = 0x9 | 0xa0;
 halfStepLut[0x9] = 0x1 | 0x80;
 halfStepLut[0x1] = 0x5 | 0x90;
 halfStepLut[0x5] = 0x4 | 0x10;
 halfStepLut[0x4] = 0x6 | 0x50;
 halfStepLut[0x6] = 0x2 | 0x40;
 halfStepLut[0x2] = 0xa | 0x60;
}

void StepperL298N::step(boolean dir)
{
  curState = lut[curState];
  if (dir) curState &= 0xf;
  else curState >>= 4;
  for (int i=1,j=0;i< 16;i*= 2,j++)
    {
    byte lvl = LOW;
    if (i&curState) lvl=HIGH;
    digitalWrite(pins[j],lvl);
    }
}


int serDataVal = LOW;
void loop()                     // run over and over again
{
  unsigned long int j;
 
  StepperL298N motor(3,4,5,6);
  motor.halfStep(true);
  motor.start();

  for (j=0;j< 1000;j++)
    {
    motor.step(1);
    digitalWrite(ledPin, j&1);   // sets the LED on
    delay(5+j/10);  // Change the delay to change the rate the motor spins
    }
  motor.halfStep(false);
  motor.start();
  for (j=0;j< 1000;j++)
    {
    motor.step(0);
    digitalWrite(ledPin, j&1);   // sets the LED on
    delay(5+j/10);
    }
}

Michael Margolis ('mem' on the Arduino.cc forum) was kind enough to let me cross-post a schematic: