Non blocking code for the 28BYJ-48 stepper motor

28bjy-48 stepper motor with wheels

One of the first things I tried when I started playing with Arduino was running a stepper motor. As I had bought 2 small 28BYJ-48 stepper motors with my first Arduino. Since I knew very little about programming I just used the Arduino stepper library. The library works but it’s not that usefull, it is a blocking library. You can’t do much else when running the motors. I then put the motors away and nearly forgot about them. Until I saw that Rocket Brand studios sells wheels that fit these motors. So I ordered a couple of the wheels. I might make a small robotic vehicle powered by these little stepper motors.
Now that I have a litle bit more experience writing code I wrote some non blocking code for my little stepper motors. The code also includes an acceleration function. It will slowly start the motor and after x number of steps it will ramp up the speed 🙂
Here is a video I made during the testing of my code:

This code will run the stepper motor in both directions for 15 seconds:

// http://www.bajdi.com
// Non blocking code for a 28BYJ-48 stepper motor controlled by an ATmega1284
// Using the delay function in void loop will break this code

//declare variables for the motor pins
const int motorPin1 = 11;	// IN1 on motor control board
const int motorPin2 = 12;	// IN2
const int motorPin3 = 13;	// IN3
const int motorPin4 = 14;	// IN4

#define runEvery(t) for (static typeof(t) _lasttime;(typeof(t))((typeof(t))millis() - _lasttime) > (t);_lasttime += (t))

unsigned long previousMicros;
unsigned long steps;
byte motor1Step = 0;
bool direction;
int stepInterval;

void setup() {
  //declare the motor pins as outputs
  pinMode(motorPin1, OUTPUT);
  pinMode(motorPin2, OUTPUT);
  pinMode(motorPin3, OUTPUT);
  pinMode(motorPin4, OUTPUT);
}

void loop(){
  // Time between steps in microseconds = stepInterval
  if (steps < 200)
  {
    stepInterval = 1800;
  }
  if (steps >= 200 && steps <= 400)
  {
    stepInterval = 1400;
  }
  if (steps > 400 && steps <= 600)
  {
    stepInterval = 1100;
  }
  if (steps > 600 && steps <= 800)
  {
    stepInterval = 900;
  }
  if (steps > 800)
  {
    stepInterval = 650;
  }

  // Switch direction every 15 seconds
  runEvery(15000)
  {
    steps = 0;  // reset steps
    if (direction == LOW)
      direction = HIGH;
    else
      direction = LOW;
  }

  if (direction == LOW)
  { 
    clockWise();
  }
  else
  {
    counterClockWise();
  }
}


void clockWise()
{
  // Clockwise stepper code
  if (micros() >= previousMicros){
    previousMicros = previousMicros+stepInterval; 
    motor1Step = motor1Step +1;

    if (motor1Step == 9){ 
      motor1Step = 1;
      steps = steps +1;
    }
  }
  switch (motor1Step){
  case 1:
    digitalWrite(motorPin4, HIGH);
    digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin2, LOW);
    digitalWrite(motorPin1, LOW);
    break;
  case 2:
    digitalWrite(motorPin4, HIGH);
    digitalWrite(motorPin3, HIGH);
    digitalWrite(motorPin2, LOW);
    digitalWrite(motorPin1, LOW);
    break;
  case 3:
    digitalWrite(motorPin4, LOW);
    digitalWrite(motorPin3, HIGH);
    digitalWrite(motorPin2, LOW);
    digitalWrite(motorPin1, LOW);
    break;
  case 4:
    digitalWrite(motorPin4, LOW);
    digitalWrite(motorPin3, HIGH);
    digitalWrite(motorPin2, HIGH);
    digitalWrite(motorPin1, LOW);
    break;
  case 5:
    digitalWrite(motorPin4, LOW);
    digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin2, HIGH);
    digitalWrite(motorPin1, LOW);
    break;
  case 6:
    digitalWrite(motorPin4, LOW);
    digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin2, HIGH);
    digitalWrite(motorPin1, HIGH);
    break;
  case 7:
    digitalWrite(motorPin4, LOW);
    digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin2, LOW);
    digitalWrite(motorPin1, HIGH); 
    break;
  case 8:
    digitalWrite(motorPin4, HIGH);
    digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin2, LOW);
    digitalWrite(motorPin1, HIGH); 
    break;
  } // end switch
}


void counterClockWise()
{
  // Counterclockwise stepper code
  if (micros() >= previousMicros){
    previousMicros = previousMicros+stepInterval; 
    motor1Step = motor1Step +1;

    if (motor1Step == 9){ 
      motor1Step = 1;
      steps = steps +1;
    }
  }
  switch (motor1Step){
  case 1:
    digitalWrite(motorPin1, HIGH);
    digitalWrite(motorPin2, LOW);
    digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin4, LOW);
    break;
  case 2:
    digitalWrite(motorPin1, HIGH);
    digitalWrite(motorPin2, HIGH);
    digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin4, LOW);
    break;
  case 3:
    digitalWrite(motorPin1, LOW);
    digitalWrite(motorPin2, HIGH);
    digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin4, LOW);
    break;
  case 4:
    digitalWrite(motorPin1, LOW);
    digitalWrite(motorPin2, HIGH);
    digitalWrite(motorPin3, HIGH);
    digitalWrite(motorPin4, LOW);
    break;
  case 5:
    digitalWrite(motorPin1, LOW);
    digitalWrite(motorPin2, LOW);
    digitalWrite(motorPin3, HIGH);
    digitalWrite(motorPin4, LOW);
    break;
  case 6:
    digitalWrite(motorPin1, LOW);
    digitalWrite(motorPin2, LOW);
    digitalWrite(motorPin3, HIGH);
    digitalWrite(motorPin4, HIGH);
    break;
  case 7:
    digitalWrite(motorPin1, LOW);
    digitalWrite(motorPin2, LOW);
    digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin4, HIGH);
    break;
  case 8:
    digitalWrite(motorPin1, HIGH);
    digitalWrite(motorPin2, LOW);
    digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin4, HIGH);
    break;
  } // end switch
}