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CCS/LAUNCHXL-F280049C: EPWM Phase shift

Luis Alfonso Fernandez Serantes
Prodigy 170 points
Part Number: LAUNCHXL-F280049C

Tool/software: Code Composer Studio

Hello, 

I have a problem with the EPWM library regarding the phase shifting... I set the PWM and it´s working fine but when I try to set a phase shift, it doesn´t work, I need to set a new counterbase so it works... 

//Here I have my PWM initialization, setting the period, etc.

    //
    // configure PWM 1 as master and Phase 2, 3 as slaves and let it pass the sync in pulse from PWM1
    //
    EPWM_disablePhaseShiftLoad(VIENNA1_DRV_EPWM_BASE);
    EPWM_setSyncOutPulseMode(VIENNA1_DRV_EPWM_BASE, EPWM_SYNC_OUT_PULSE_ON_COUNTER_ZERO);

    EPWM_enablePhaseShiftLoad(VIENNA2_DRV_EPWM_BASE);
    EPWM_setSyncOutPulseMode(VIENNA2_DRV_EPWM_BASE, EPWM_SYNC_OUT_PULSE_ON_EPWMxSYNCIN);

    EPWM_setPhaseShift(VIENNA2_DRV_EPWM_BASE, 0);
    EPWM_setCountModeAfterSync(VIENNA2_DRV_EPWM_BASE, EPWM_COUNT_MODE_UP_AFTER_SYNC);
    EPWM_setTimeBaseCounter(VIENNA2_DRV_EPWM_BASE, 2000);                                                                                        //Although PhaseShift is set to 0, because of base counter I have a phase shift.

    EPWM_setSyncOutPulseMode(VIENNA3_DRV_EPWM_BASE, EPWM_SYNC_OUT_PULSE_ON_EPWMxSYNCIN);
    EPWM_setCountModeAfterSync(VIENNA3_DRV_EPWM_BASE, EPWM_COUNT_MODE_UP_AFTER_SYNC);
    EPWM_enablePhaseShiftLoad(VIENNA3_DRV_EPWM_BASE);
    EPWM_setPhaseShift(VIENNA3_DRV_EPWM_BASE, 2000);                                                                                                   // I set the PhaseShift but it´s not working at all...

Could you help me, please?

Thank you very much.

BR,

Luis

  • 0
    TI__Genius 10845 points

    Hi,

    Can you confirm the PWM instances used in the code above? Is it PWM1 as master and PWM 2 and 3 as slaves ? Also can you share other PWM configurations like period, duty, action qualifier as well?

    Thanks

    Vasudha

  • 0 in reply to Vasudha Bhadoria
    Prodigy 170 points

    Hi Vasudha,

    Thanks for your support.

    Yes, the PWM1 is master and PWM2 and PWM3 are slaves.

    The configuration of the PWM is done as follows:

        EPWM_setClockPrescaler(PWMbase,VIENNA_EPWM_EPWMCLK_DIV, VIENNA_EPWM_HSCLK_DIV);
        EPWM_setEmulationMode(PWMbase, EPWM_EMULATION_FREE_RUN);
        //
        // Configure ePWM for count-up operation
        //
        EPWM_setTimeBaseCounter(PWMbase, 0);
        EPWM_setTimeBasePeriod(PWMbase, VIENNA_EPWM_TBPRD);
        EPWM_setPeriodLoadMode(PWMbase, EPWM_PERIOD_SHADOW_LOAD);
        EPWM_setTimeBaseCounterMode(PWMbase, EPWM_COUNTER_MODE_UP);
        EPWM_setPhaseShift(PWMbase,0);

        //
        // Use shadow mode to update CMPA on TBPRD
        //
        EPWM_setCounterCompareValue(PWMbase, EPWM_COUNTER_COMPARE_A, 0);
        EPWM_setCounterCompareShadowLoadMode(PWMbase, EPWM_COUNTER_COMPARE_A, EPWM_COMP_LOAD_ON_CNTR_PERIOD);

        // Configure Action Qualifier SubModule to:

        //     Output A Low when TBCTR=0

        EPWM_setActionQualifierShadowLoadMode(PWMbase, EPWM_ACTION_QUALIFIER_A, EPWM_AQ_LOAD_ON_CNTR_ZERO);
        EPWM_setActionQualifierAction(PWMbase, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_LOW, EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);

        //     Output A High when TBCTR=CMPA
        EPWM_setActionQualifierAction(PWMbase, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_HIGH, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);

        //     Output B High when TBCTR=0
        EPWM_setActionQualifierAction(PWMbase, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_HIGH, EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);

        //     Output B Low when TBCTR=CMPA
        EPWM_setActionQualifierAction(PWMbase, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_LOW, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);

        //
        // Configure Dead Band Generator for active high complementary PWMs
        //
        EPWM_setDeadBandDelayMode(PWMbase, EPWM_DB_RED, true);
        EPWM_setDeadBandDelayMode(PWMbase, EPWM_DB_FED, true);

        EPWM_setRisingEdgeDeadBandDelayInput(PWMbase, EPWM_DB_INPUT_EPWMA);
        EPWM_setFallingEdgeDeadBandDelayInput(PWMbase, EPWM_DB_INPUT_EPWMA);

        EPWM_setDeadBandDelayPolarity(PWMbase, EPWM_DB_FED, EPWM_DB_POLARITY_ACTIVE_LOW);
        EPWM_setDeadBandDelayPolarity(PWMbase, EPWM_DB_RED, EPWM_DB_POLARITY_ACTIVE_HIGH);

        EPWM_setFallingEdgeDelayCount(PWMbase, VIENNA_EPWM_DEADBAND_FED);
        EPWM_setRisingEdgeDelayCount(PWMbase, VIENNA_EPWM_DEADBAND_RED);

    Thanks again!

    Luis

  • 0 in reply to Vasudha Bhadoria
    Prodigy 170 points

    Dear Vasudha,

    I´ve found the problem but I don´t know how to solve it... This picture gives a good description of my problem:

    When I use PWM1 and PWM2, the shift is working fine. The problem that I have using other PWM and synchronising them to PWM1 is that I need to select the input sync event.

    How do I do this with the epwm.h library? How is the function called to select the SYNCIN event? I cannot find a function to do this... could you help me, please?

    Best regards,

    Luis

  • 0 in reply to Luis Alfonso Fernandez Serantes
    Prodigy 170 points

    I´ve found how to solve it:

        SysCtl_setSyncInputConfig(SYSCTL_SYNC_IN_EPWM4, SYSCTL_SYNC_IN_SRC_EXTSYNCIN1);
        SysCtl_setSyncInputConfig(SYSCTL_SYNC_IN_EPWM7, SYSCTL_SYNC_IN_SRC_EXTSYNCIN1);

    Adding this lines to sync the input clocks ;) 

    Thanks!