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LAUNCHXL-F280025C: HRPWM CMPAHR doesn't cover all range

Michael Mor Yosef
Prodigy 190 points
Part Number: LAUNCHXL-F280025C

Hi,

I tried to use user manual example (above picture)

And run it via CCS using this code:

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periodVal = EPWM_getTimeBasePeriod(EPWM1_BASE);
regValCMPA = (int)(PWMDuty * periodVal);
_temp = (PWMDuty * (float)(periodVal));
_temp = (__fracf32(_temp)) ;
regValCMPAHR =( _temp * MEP_ScaleFactor + 0.5);
regValCMPAHR = (regValCMPAHR ) << 8U;
HWREG(EPWM1_BASE + HRPWM_O_CMPA) = (((long)regValCMPA) << 16U) |
regValCMPAHR;
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

While debugging I got the following values that go to CMPA CMPAHR registers:

But when measuring D.C. with scope I got only 12.06% instead of 12.32% as shown on debug picture under PWMDuty expression.
And when I try manually increase CMPHR so D.C. will achieve 12.32% the max expression (0xff00) I got the above PWMDuty.

Maybe the code isnt implemeted well? attaching example from datasheet


I'll Apricate your help.
Michael

  • 0
    TI__Genius 9261 points

    Hello Michael,

    Apologies for the delayed response. Were you using the SFO library? If not, I would highly recommend doing so, it greatly simplifies the overall process of working with the HRPWM.

    For the specific issue, take a look at the following code snippet from section 17.15.2.1 of the device TRM (which assumes the SFO library is being used):

    At a glance, I'd note that you convert to long instead of uint32_t. What happens if you adjust your calculations to result in an unsigned int output?

    Regards,
    Jason Osborn