TMS320F28377S: Can't get CAD or CBD to work

Andrew Barnett

Intellectual 870 points

Part Number: TMS320F28377S

I am trying to replicate the behavior of Figure 14-30 in the TRM (SPRUHX5F) using EPwm6A.

The up-count settings work as expected but the down-count settings don't work.

EPwm6 register settings are as follows:

EPwm6Regs.TBCTL.bit.CTRMODE = TB_COUNT_UPDOWN;

EPwm6Regs.CMPCTL.bit.LOADAMODE = 0; /* Load on CTR = 0 */
EPwm6Regs.CMPCTL.bit.LOADBMODE = 0; /* Load on CTR = 0 */
EPwm6Regs.CMPCTL.bit.SHDWAMODE = 0; /* Shadow Enabled */
EPwm6Regs.CMPCTL.bit.SHDWBMODE = 0; /* Shadow Enabled */
EPwm6Regs.CMPCTL.bit.LOADASYNC = 0; /* Use LOADAMODE */
EPwm6Regs.CMPCTL.bit.LOADBSYNC = 0; /* Use LOADBMODE */

EPwm6Regs.AQCTL.bit.LDAQAMODE = 0; /* Load on CTR = 0 */
EPwm6Regs.AQCTL.bit.LDAQBMODE = 0; /* Load on CTR = 0 */
EPwm6Regs.AQCTL.bit.SHDWAQAMODE = 1; /* Shadow enabled */
EPwm6Regs.AQCTL.bit.SHDWAQBMODE = 1; /* Shadow enabled */
EPwm6Regs.AQCTL.bit.LDAQASYNC = 0; /* Use LDAQAMODE */
EPwm6Regs.AQCTL.bit.LDAQBSYNC = 0; /* Use LDAQBMODE */

EPwm6Regs.TBPRD = 166;
EPwm6Regs.CMPA.bit.CMPA = 120;
EPwm6Regs.CMPB.bit.CMPB = (EPwm6Regs.TBPRD - EPwm6Regs.CMPA.bit.CMPA); /* CMPB = 46 */

EPwm6Regs.AQCTLA.bit.ZRO = AQ_CLEAR;
EPwm6Regs.AQCTLA.bit.PRD = AQ_NO_ACTION;
EPwm6Regs.AQCTLA.bit.CAU = AQ_SET;
EPwm6Regs.AQCTLA.bit.CAD = AQ_NO_ACTION;
EPwm6Regs.AQCTLA.bit.CBU = AQ_NO_ACTION;
EPwm6Regs.AQCTLA.bit.CBD = AQ_CLEAR;

With these settings I am expecting the behavior as seen in Figure 14-30:

What I'm actually getting is shown in the scope plot below. Channel 1 is EPwm2A (its rising edge corresponds to EPwm2.TBCNT = EPwm6.TBCNT = 0). Ch2 = EPwm6A. Deadband has been zero'd for clarity.

Note that EPwm6A goes high at TBCNT = CMPA on up-count, as expected. It does NOT go low at TBCNT = CMPB on down-count but instead stays high until TBCNT = 0.

I have tried swapping the values for EPwm6Regs.CMPA.bit.CMPA and EPwm6Regs.CMPB.bit.CMPB (i.e. CMPA = 46, CMPB = 120) and the result is the same.

I've also tried setting both EPwm6Regs.CMPCTL.bit.LOADAMODE and EPwm6Regs.CMPCTL.bit.LOADBMODE to 1 and 2 (PRD load and both ZRO and PRD load) also wiht no effect.

Am I mis-setting a register, or possibly attempting something that can't be done? Thanks in advance for any insight.

over 5 years ago

0 Nima Eskandari over 5 years ago

TI__Guru 52040 points

1. Try immediate mode, lets see if that changes anything.

2. Check after the settings are done in the debugger to make sure the values you have set for your registers took effect.

Nima

0 Andrew Barnett over 5 years ago in reply to Nima Eskandari

Intellectual 870 points

Nima,

I changed AQCTL to load immediate as shown below and it didn't change the behavior.

Could you summarize the register settings necessary to implement the EPWMxA waveform in Figure 30. I think if I can get that working I'll be able to resolve this issue.

Thanks for your assistance.

EPwm6Regs.AQCTL.bit.LDAQAMODE = 0;
EPwm6Regs.AQCTL.bit.LDAQBMODE = 0;

EPwm6Regs.AQCTL.bit.SHDWAQAMODE = 0;
EPwm6Regs.AQCTL.bit.SHDWAQBMODE = 0;

EPwm6Regs.AQCTL.bit.LDAQASYNC = 0;
EPwm6Regs.AQCTL.bit.LDAQBSYNC = 0;

0 Andrew Barnett over 5 years ago in reply to Andrew Barnett

Intellectual 870 points

Sorry, I meant Figure 14-30, as shown above

0 Nima Eskandari over 5 years ago in reply to Andrew Barnett

TI__Guru 52040 points

I’ll send you a simple example for this.

0 Nima Eskandari over 5 years ago in reply to Nima Eskandari

TI__Guru 52040 points

Still working on this I will post it when it's ready!

0 Nima Eskandari over 5 years ago in reply to Nima Eskandari

TI__Guru 52040 points

void initEPWM(uint32_t base)
{
    //
    // Set-up TBCLK
    //
    EPWM_setTimeBasePeriod(base, EPWM_TIMER_TBPRD);
    EPWM_setPhaseShift(base, 0U);
    EPWM_setTimeBaseCounter(base, 0U);

    //
    // Set Compare values
    //
    EPWM_setCounterCompareValue(base,
                                EPWM_COUNTER_COMPARE_A,
                                EPWM_TIMER_TBPRD/2);
    EPWM_setCounterCompareValue(base,
                                EPWM_COUNTER_COMPARE_B,
                                EPWM_TIMER_TBPRD/4*3);

    //
    // Set up counter mode
    //
    EPWM_setTimeBaseCounterMode(base, EPWM_COUNTER_MODE_UP_DOWN);
    EPWM_disablePhaseShiftLoad(base);
    EPWM_setClockPrescaler(base,
                           EPWM_CLOCK_DIVIDER_8,
                           EPWM_HSCLOCK_DIVIDER_1);

    //
    // Set up shadowing
    //
    EPWM_setCounterCompareShadowLoadMode(base,
                                         EPWM_COUNTER_COMPARE_A,
                                         EPWM_COMP_LOAD_ON_CNTR_ZERO);
    EPWM_setCounterCompareShadowLoadMode(base,
                                         EPWM_COUNTER_COMPARE_B,
                                         EPWM_COMP_LOAD_ON_CNTR_ZERO);

    //
    // Set actions
    //

    EPWM_setActionQualifierAction(base,
                                  EPWM_AQ_OUTPUT_A,
                                  EPWM_AQ_OUTPUT_LOW,
                                  EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);
    EPWM_setActionQualifierAction(base,
                                  EPWM_AQ_OUTPUT_A,
                                  EPWM_AQ_OUTPUT_HIGH,
                                  EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);
    EPWM_setActionQualifierAction(base,
                                  EPWM_AQ_OUTPUT_A,
                                  EPWM_AQ_OUTPUT_NO_CHANGE,
                                  EPWM_AQ_OUTPUT_ON_TIMEBASE_PERIOD);
    EPWM_setActionQualifierAction(base,
                                  EPWM_AQ_OUTPUT_A,
                                  EPWM_AQ_OUTPUT_LOW,
                                  EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPB);


    EPWM_setActionQualifierAction(base,
                                  EPWM_AQ_OUTPUT_B,
                                  EPWM_AQ_OUTPUT_LOW,
                                  EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);
    EPWM_setActionQualifierAction(base,
                                  EPWM_AQ_OUTPUT_B,
                                  EPWM_AQ_OUTPUT_NO_CHANGE,
                                  EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);
    EPWM_setActionQualifierAction(base,
                                  EPWM_AQ_OUTPUT_B,
                                  EPWM_AQ_OUTPUT_HIGH,
                                  EPWM_AQ_OUTPUT_ON_TIMEBASE_PERIOD);
    EPWM_setActionQualifierAction(base,
                                  EPWM_AQ_OUTPUT_B,
                                  EPWM_AQ_OUTPUT_NO_CHANGE,
                                  EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPB);



    //
    // Interrupt where we will change the Compare Values
    // Select INT on Time base counter zero event,
    // Enable INT, generate INT on 1rd event
    //
    EPWM_setInterruptSource(base, EPWM_INT_TBCTR_ZERO);
    EPWM_enableInterrupt(base);
    EPWM_setInterruptEventCount(base, 1U);
}

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TMS320F28377S: Can't get CAD or CBD to work