Controlling stepper motors in real time with arduino

Using Arduino Motors, Mechanics, Power and CNC
1

hello, I have been trying to control two stepper motors in my balancing robot project. I first tried to do it with ISR and counting the interruptions, however that makes the whole system non linear which is hard for PID. There is a program on github thats seems to do the trick but I cant figure out what's going on in the code. Here is linkt to the repository on github https://github.com/JJulio/b-robot/blob/master/B_ROBOT/B_ROBOT.ino

If anyone knows whats going on with the perdiods/subperiods I would be veryu grateful for some explanations or sources with information about it

ISR(TIMER1_COMPA_vect)
{
  counter_m[0]++;
  counter_m[1]++;
  if (counter_m[0] >= period_m[0][period_m_index[0]])
    {
    counter_m[0] = 0;
    if (period_m[0][0]==ZERO_SPEED)
      return;
    if (dir_m[0])
      SET(PORTB,4);  // DIR Motor 1
    else
      CLR(PORTB,4);
    // We need to wait at lest 200ns to generate the Step pulse...
    period_m_index[0] = (period_m_index[0]+1)&0x07; // period_m_index from 0 to 7
    //delay_200ns();
    SET(PORTD,7); // STEP Motor 1
    delayMicroseconds(1);
    CLR(PORTD,7);
    }
  if (counter_m[1] >= period_m[1][period_m_index[1]])
    {
    counter_m[1] = 0;
    if (period_m[1][0]==ZERO_SPEED)
      return;
    if (dir_m[1])
      SET(PORTC,7);   // DIR Motor 2
    else
      CLR(PORTC,7);
    period_m_index[1] = (period_m_index[1]+1)&0x07;
    //delay_200ns();
    SET(PORTD,6); // STEP Motor 1
    delayMicroseconds(1);
    CLR(PORTD,6);
    }
}


// Dividimos en 8 subperiodos para aumentar la resolucion a velocidades altas (periodos pequeños)
// subperiod = ((1000 % vel)*8)/vel;
// Examples 4 subperiods:
// 1000/260 = 3.84  subperiod = 3
// 1000/240 = 4.16  subperiod = 0
// 1000/220 = 4.54  subperiod = 2
// 1000/300 = 3.33  subperiod = 1 
void calculateSubperiods(uint8_t motor)
{
  int subperiod;
  int absSpeed;
  uint8_t j;
  
  if (speed_m[motor] == 0)
    {
    for (j=0;j<8;j++)
      period_m[motor][j] = ZERO_SPEED;
    return;
    }
  if (speed_m[motor] > 0 )   // Positive speed
    {
    dir_m[motor] = 1;
    absSpeed = speed_m[motor];
    }
  else                       // Negative speed
    {
    dir_m[motor] = 0;
    absSpeed = -speed_m[motor];
    }
    
  for (j=0;j<8;j++)
    period_m[motor][j] = 1000/absSpeed;
  // Calculate the subperiod. if module <0.25 => subperiod=0, if module < 0.5 => subperiod=1. if module < 0.75 subperiod=2 else subperiod=3
  subperiod = ((1000 % absSpeed)*8)/absSpeed;   // Optimized code to calculate subperiod (integer math)
  if (subperiod>0)
   period_m[motor][1]++;
  if (subperiod>1)
   period_m[motor][5]++;
  if (subperiod>2)
   period_m[motor][3]++;
  if (subperiod>3)
   period_m[motor][7]++;
  if (subperiod>4)
   period_m[motor][0]++;
  if (subperiod>5)
   period_m[motor][4]++;
  if (subperiod>6)
   period_m[motor][2]++;
  
  // DEBUG
  /*
  if ((motor==0)&&((debug_counter%10)==0)){
    Serial.print(1000.0/absSpeed);Serial.print("\t");Serial.print(absSpeed);Serial.print("\t");
    Serial.print(period_m[motor][0]);Serial.print("-");
    Serial.print(period_m[motor][1]);Serial.print("-");
    Serial.print(period_m[motor][2]);Serial.print("-");
    Serial.println(period_m[motor][3]);
    }
  */  
}

also, why calculating the subperiods is so out of order - first is 1 then 5, then 3 and so on... the 6 is missing, please help

2

To make is short: What are You talking about and what are You doing?
Snippets of code and snippets of system description are never popular.
Please post code according to the advice given in How to get the best out of this forum - Using Arduino / IDE 1.x - Arduino Forum

Drawing a logic block diagram of the system would also help us.

3

I am trying to build self balancing robot and write the code for it on my own. Right now I am trying to understand someones code on the topic. I posted whole github repository, and only a small snippet of code because I didnt want to paste 1000 lines of code here as the ISR is the problem for me

4

Posting a link to .ino is not what You're expected to do. Many helpers use devices not able to download. In general downloading unknown stuff daily is just not accepted be helpers. Please read the link to advice.

That's the way to get problems, importing unknown code.
The snippet You posted looks poor. The lack of comments makes it look as a hobbyist making it. Code is not documneted by the code itself. The larger the code is the wider the shelf keeping the binders of documents is.

I'll spare You further comments.