TMS320F28386S: HRPWM Jump When Coarse Count changes - Not Solved

Hi Santhosh,

Can you explain a bit further on major count changes? Does this mean you're going from a CMPA value of 499 to some value 800 for example?

We have a FAQ on what may be causing common HRPWM issues, please refer to this for setup.

Best,

Ryan Ma

Thanks for replying,... By Major count, I meant the change in CMPA value. And Minor counts being CMPAHR. My overall CMPA change is only 4-5 counts for the entire waveform shared. we went HRPWM to improve the resolution. I am expecting the HRPWM to bridge between two CMPA values making the Step type of output into a smooth ramp. 

As per the datasheet, there shall be MEP Scale Factor number of steps provided by the HRPWM within two CMPA Values. so as the factional part goes from 0 to 1, the output should have bridged the region between two CMPA values right ? Which is not what am seeing. my init is something like this...

HRPWM_setEmulationMode(base, EPWM_EMULATION_FREE_RUN);
    EPWM_setTimeBasePeriod(base, INIT_mPRD_VAL);
    HRPWM_setTimeBaseCounter(base, 0);

    EPWM_setCounterCompareValue(base, EPWM_COUNTER_COMPARE_A, INIT_mPRD_VAL >> 1);
    EPWM_setCounterCompareValue(base, EPWM_COUNTER_COMPARE_B, INIT_mPRD_VAL >> 1);

    HRPWM_setTimeBaseCounterMode(base, EPWM_COUNTER_MODE_UP_DOWN);
    HRPWM_disablePhaseShiftLoad(base);
    HRPWM_setClockPrescaler(base, EPWM_CLOCK_DIVIDER_1, EPWM_HSCLOCK_DIVIDER_1);
    HRPWM_setPhaseShift(base, (uint32_t)phaseCount << 8U);
    EPWM_enablePhaseShiftLoad(base);
    HRPWM_enablePhaseShiftLoad(base);
    EPWM_enableSyncOutPulseSource(base, EPWM_SYNC_OUT_PULSE_ON_CNTR_ZERO);
    EPWM_setSyncInPulseSource(base, syncInSource);

    HRPWM_setCounterCompareShadowLoadMode(base, EPWM_COUNTER_COMPARE_A,
                                          EPWM_COMP_LOAD_ON_CNTR_ZERO_PERIOD);
    HRPWM_setCounterCompareShadowLoadMode(base, EPWM_COUNTER_COMPARE_B,
                                          EPWM_COMP_LOAD_ON_CNTR_ZERO_PERIOD);

    HRPWM_setActionQualifierAction(base, EPWM_AQ_OUTPUT_A,
                                   EPWM_AQ_OUTPUT_LOW,
                                   EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);
    HRPWM_setActionQualifierAction(base, EPWM_AQ_OUTPUT_A,
                                   EPWM_AQ_OUTPUT_HIGH,
                                   EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPA);

    HRPWM_disableRisingEdgeDelayCountShadowLoadMode(base);
    HRPWM_disableFallingEdgeDelayCountShadowLoadMode(base);
    EPWM_disableDeadBandControlShadowLoadMode(base);

    HRPWM_setRisingEdgeDeadBandDelayInput(base,
                                          EPWM_DB_INPUT_EPWMA);
    HRPWM_setFallingEdgeDeadBandDelayInput(base,
                                           EPWM_DB_INPUT_EPWMA);

    HRPWM_setRisingEdgeDelayCountShadowLoadMode(base,
                                                EPWM_RED_LOAD_ON_CNTR_ZERO_PERIOD);
    HRPWM_setFallingEdgeDelayCountShadowLoadMode(base,
                                                EPWM_FED_LOAD_ON_CNTR_ZERO_PERIOD);

    EPWM_setDeadBandDelayPolarity(base, EPWM_DB_FED, EPWM_DB_POLARITY_ACTIVE_LOW);
    EPWM_setDeadBandDelayMode(base, EPWM_DB_RED, true);
    EPWM_setRisingEdgeDelayCount(base, INIT_mDEAD_BAND_VAL_RED);
    EPWM_setDeadBandDelayMode(base, EPWM_DB_FED, true);
    EPWM_setFallingEdgeDelayCount(base, INIT_mDEAD_BAND_VAL_FED);

    HRPWM_setMEPEdgeSelect(base, HRPWM_CHANNEL_A,
                           HRPWM_MEP_CTRL_RISING_AND_FALLING_EDGE);
    HRPWM_setMEPControlMode(base,HRPWM_CHANNEL_A,HRPWM_MEP_DUTY_PERIOD_CTRL);

    HRPWM_setMEPEdgeSelect(base, HRPWM_CHANNEL_B,
                           HRPWM_MEP_CTRL_RISING_AND_FALLING_EDGE);
    HRPWM_setMEPControlMode(base,HRPWM_CHANNEL_B,HRPWM_MEP_DUTY_PERIOD_CTRL);

    HRPWM_setCounterCompareShadowLoadEvent(base, HRPWM_CHANNEL_A, HRPWM_LOAD_ON_CNTR_ZERO_PERIOD);
    HRPWM_setCounterCompareShadowLoadEvent(base, HRPWM_CHANNEL_B, HRPWM_LOAD_ON_CNTR_ZERO_PERIOD);

    HRPWM_enableAutoConversion(base);
    HRPWM_enablePeriodControl(base);

And i update the CMPA/CMPAHR value as 

HRPWM_setCounterCompareValue(EPWM3_BASE, HRPWM_COUNTER_COMPARE_A, (uint32_t)(fS1Ch3 * 256.0F));

fS1Ch3 is a floating value of the CMP register. This is as per the hrpwm_ex1_duty_sfo example.

I had also tried the loading of CMPA and CMPAHR separately too. Same results.

Thanks

Santhosh

Hi Santhosh, 

Are you only setting CMPA and CMPAHR?

Are you following the limitation for reaching the 3 clock cycle boundary at TBPRD / ZRO?

Best,

Ryan Ma

Hi,

No my duty starts from 50% and goes up or down. I dont get close to 3 counts issue as mentioned in the datasheet. I did not find any other solution yet. So any other clue should help.

Thanks,

Santhosh

If you're not using CMPB/CMPBHR, I would recommend still writing at least a value of 1 in the CMPBHR register. 

Can you confirm that the HR portion you're writing sweeps the full HR i.e. 50.0 -> 50.99% then goes to 60%?

Is the sync signal coming every period from another PWM? If this is the case, please do not sync every period or zro event because this will cause jitter that you may be seeing. Instead you only need to sync once every so often.

Best,

Ryan Ma

Hi,

Loading CMPB and CMPBHR with non zero values

Yes the HR Portion is going through the full range of values with equal steps. I read back the Compare Value during the CMPA transition.. shown here

CMPA_FULL is manually calculated by combining the CMPA and CMPA HR. CMPA and CMPA_FULL are on left Y-axis and CMPAHR is on right side Y-axis. I ll check on the sync

Thanks

Santhosh

For the Sync related point.. yes the two pulses are meant to be in sync in my case, so i use the first PWM as reference (1A) and make Phase as zero for second pwm (2A).... first one is not in sync with any external source. I enable the syncout from EPWM1 and use that as syncin source for EPWM2

EPWM_enableSyncOutPulseSource(EPWM1_BASE, EPWM_SYNC_OUT_PULSE_ON_CNTR_ZERO); //in epwm1 init

EPWM_setSyncInPulseSource(EPWM2_BASE, EPWM_SYNC_IN_PULSE_SRC_SYNCOUT_EPWM1); // in epwm2 init..