A simple PI controller for a motor and encoder combination

Project_3.ino

/* interrupt routine for Rotary Encoders
   tested with Noble RE0124PVB 17.7FINB-24 http://www.nobleusa.com/pdf/xre.pdf - available at pollin.de
   and a few others, seems pretty universal

   The average rotary encoder has three pins, seen from front: A C B
   Clockwise rotation A(on)->B(on)->A(off)->B(off)
   CounterCW rotation B(on)->A(on)->B(off)->A(off)

   and may be a push switch with another two pins, pulled low at pin 8 in this case
   [email protected] 20120107

*/

// usually the rotary encoders three pins have the ground pin in the middle
enum PinAssignments {
  encoderPinA = 2,   // rigth
  encoderPinB = 3,   // left
  clearButton = 8    // another two pins
};

int kp = 10;
int ki = 10;
byte u =0;
double dt = .001;
double Ii = 0;
double Il = 1;
double ei = 1;
double dspeed = 30;
double p = 0;

const int AIA = 11;  // (pwm) pin 9 connected to pin A-IA 
const int AIB = 5;  // (pwm) pin 5 connected to pin A-IB 
 
byte speed = 0;  // change this (0-255) to control the speed of the motors

volatile int encoderPos = 0;  // a counter for the dial
unsigned int lastReportedPos = 1;   // change management
static boolean rotating=false;      // debounce management

// interrupt service routine vars
boolean A_set = false;              
boolean B_set = false;

 int flag, count;
 double time, f, rps;

void setup() {

  pinMode(encoderPinA, INPUT); 
  pinMode(encoderPinB, INPUT); 
  pinMode(clearButton, INPUT);
 // turn on pullup resistors
  digitalWrite(encoderPinA, HIGH);
  digitalWrite(encoderPinB, HIGH);
  digitalWrite(clearButton, HIGH);

// encoder pin on interrupt 0 (pin 2)
  attachInterrupt(0, doEncoderA, CHANGE);
// encoder pin on interrupt 1 (pin 3)
  attachInterrupt(1, doEncoderB, CHANGE);

  pinMode(AIA, OUTPUT); // set pins to output
  pinMode(AIB, OUTPUT);
  
  // initialize Timer1
  cli();          // disable global interrupts
  TCCR1A = 0;     // set entire TCCR1A register to 0
  TCCR1B = 0;     // same for TCCR1B
 
  // set compare match register to desired timer count:
  OCR1A = 249;
  // turn on CTC mode:
  TCCR1B |= (1 << WGM12);
  // Set CS10 and CS12 bits for 64 prescaler:
  TCCR1B |= (1 << CS10);
  //TCCR1B |= (1 << CS11);
  TCCR1B |= (1 << CS11);
  // enable timer compare interrupt:
  TIMSK1 |= (1 << OCIE1A);
  // enable global interrupts:
  sei();
    
  Serial.begin(9600);  // output
}

// main loop, work is done by interrupt service routines, this one only prints stuff
void loop() { 
  rotating = true;  // reset the debouncer

  if (lastReportedPos != encoderPos) {
//    Serial.print("Index:");
//    Serial.println(encoderPos, DEC);
    lastReportedPos = encoderPos;
  }
  if (digitalRead(clearButton) == LOW )  {
    encoderPos = 0;
  }
  ei = dspeed - f;
  Integral();
  Proportional();
  u = (ki*Ii) + p;
  forward();
  
  Serial.println(f);
}

void Integral(){
  Ii = Il + (dt*ei);
  Il = Ii;

}

void Proportional(){
  p = ei*kp;
}
void forward()
{
  analogWrite(AIA, u);
  analogWrite(AIB, 0);
}

// Interrupt on A changing state
void doEncoderA(){
  // debounce
  if ( rotating ) delay (1);  // wait a little until the bouncing is done

  // Test transition, did things really change? 
  if( digitalRead(encoderPinA) != A_set ) {  // debounce once more
    A_set = !A_set;

    // adjust counter + if A leads B
    if ( A_set && !B_set ){ 
      encoderPos += 1;
      flag = 1;
    }
    rotating = false;  // no more debouncing until loop() hits again
  }
}

// Interrupt on B changing state, same as A above
void doEncoderB(){
  if ( rotating ) delay (1);
  if( digitalRead(encoderPinB) != B_set ) {
    B_set = !B_set;
    //  adjust counter - 1 if B leads A
    if( B_set && !A_set ){ 
      encoderPos -= 1;
      flag = 1;
    }
    rotating = false;
  }
}

ISR(TIMER1_COMPA_vect){
  if(flag == 0){
    count++;
  }
  else{
    time = (double)count*.001;
    f = 1/time;
    rps = f/20;
    count = 0;
    flag = 0;
    
  }
}