Stepper Motor Speed Control with Rotary Encoder - Arduino Tutorial

// defines pins numbers
const int stepPin = 5;
const int dirPin = 2;
const int enPin = 8;


//

int val;
int encoder0PinA = 3;
int encoder0PinB = 4;
int encoder0Pos = 0;
int encoder0PinALast = LOW;
int n = LOW;
int maxKnob = 20;
int stepperSpeed = 2000;
int maxSpeed     = 600;
int minSpeed     = 2000;

void setup() {

  Serial.begin(9600);

  pinMode (encoder0PinA, INPUT);
  pinMode (encoder0PinB, INPUT);



  // Sets the two pins as Outputs
  pinMode(stepPin,OUTPUT);
  pinMode(dirPin,OUTPUT);

  pinMode(enPin,OUTPUT);
  digitalWrite(enPin,LOW);

  // Set Dir to Home switch
  digitalWrite(dirPin,HIGH); // Enables the motor to move in a particular direction


}
void loop() {

 
        motorStep(1);

 
 
 

    getKnob();

}
void motorStep( int MAX){

   for(int x = 0; x < MAX; x++) {
        digitalWrite(stepPin,HIGH);
        delayMicroseconds(stepperSpeed);
        digitalWrite(stepPin,LOW);
        delayMicroseconds(stepperSpeed);
      }
   
}
void getKnob(){
     n = digitalRead(encoder0PinA);
  if ((encoder0PinALast == LOW) && (n == HIGH)) {
    if (digitalRead(encoder0PinB) == LOW) {
      encoder0Pos--;
    } else {
      encoder0Pos++;
    }
    if( encoder0Pos > maxKnob ){
         encoder0Pos = maxKnob;
    }
    else if( encoder0Pos < 0 ){
         encoder0Pos = 0;
    }

    int r= encoder0Pos * 100;

    r = minSpeed - r;
    r = (r < maxSpeed)?maxSpeed : r;

    stepperSpeed = r;
 
   // Serial.print (encoder0Pos);
  //  Serial.println();

    Serial.println ( r );
  }
  encoder0PinALast = n;
}