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eQEP Problem

Guillermo Catuogno
Prodigy 225 points

Hello,Im reading position with encoder, the problem is that sometimes the count jump to erroneous date, like in the image:

I read position in a interrupt at 10KHz


 

I configure the EQeP fron this way:

void encoder(void)
{
                EQep2Regs.QDECCTL.bit.QSRC=00;  // El modulo cuenta en cuadratura
                EQep2Regs.QEPCTL.bit.FREE_SOFT=2; //unaffected by emulation suspend
                EQep2Regs.QEPCTL.bit.PCRM=00; // QPOSCNT se reseta con cada cero (Un0)
                EQep2Regs.QEPCTL.bit.UTE=0;  //1 Habilita la unidad de Timeout
                EQep2Regs.QEPCTL.bit.QCLM=0;  //1 Latch on unit time out
                EQep2Regs.QEPCTL.bit.IEL = 1; // IEL_RISING
                EQep2Regs.QEPCTL.bit.IEI = 2; // IEL_RISING
                EQep2Regs.QPOSMAX=4*1024 - 1; //  valor maximo del encoder
                EQep2Regs.QEPCTL.bit.QPEN=1;  //1 Habilita QEP
                 //EQep2Regs.QUPRD=150000;  // unidad de tiempo en 100Hz si SYSCLKOTT=150MHz

 

and in the interrupt I have the next code:

 

interrupt void cpu_timer0_isr(void)
{
    CpuTimer0.InterruptCount++;
   
    x_ac= EQep2Regs.QPOSCNT;
   
    if (k<512)
       {Pos[k]=x_ac;
        k=k+1;}   
    else
        {k=0;}

I have a Vector of 512 point so I can storage the information. Can Sombody help me??

  • 0
    TI__Intellectual 2795 points

    Wilson,

    Do you have other interrupt sources with higher priorities than cpu_timer0_isr ? If so give cpu_timer0_isr the highest possible priority and see if the problem goes away.

    Thanks

    Noah

  • 0 in reply to Noah:Berhanu
    Prodigy 225 points

    Hello Noah, i dont have another interrupt, Is just one.

     

      I think the problem may be the configuration of eQEP, the signal from the encoder I have measured with oscilloscope and are Ok.

     

     

  • 0
    Genius 5885 points

    Hi Wilson

    QEP is running fine, what you most probably see is the effect of storing the data without any trigger. So the values from 0 to 150 are current samples and values from 150 to 512 are from previous acquisition.

    Regards, Mitja

  • 0 in reply to Mitja Nemec
    Prodigy 225 points

    Hello Mitja, how do that? trigger data?

  • 0 in reply to Guillermo Catuogno
    Genius 5885 points

    Hi Wilson,

    one way of doing it is to replace the

    else
        {k=0;}

    statement with something like

    else
        {if ((pos_prev > EQep2Res.QPOSCNT) && (an GPIO == 1)    )   

            {k = 0;}

        pos_prev = EQep2Res.QPOSCNT;

        }

    obviously you will have to define a variable

    static unsigned int EQep2Res.QPOSCNT;

    so you will start to write in the buffer only and only when you will press a key (you might replace that with a SW switch which you change it through watch windows) and (presuming positive direction of rotation) QPOSCNT will rollover.

    Regards, Mitja

     

    An idea for TI support people: You could overhaul DLOG module so that it would:

    - support long and float types

    - have a separate trigger channel (trigger not bound to buffer1 or *ptr1)

    - support normal scope triggering modes (auto, normal and single shot)

    - support positive and negative slope on the trigger

    - support variable channel number (maybe through preprocesor directives)

     

  • 0 in reply to Mitja Nemec
    Prodigy 225 points

    Hello Mijta, I tried to trigger by software and work fine, yo have right! thanks a lot!!