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Regarding HRPWM in piccolo

Amtech
Genius 4575 points
Other Parts Discussed in Thread: TMS320F28069, CONTROLSUITE

Hi,

I am using TMS320F28069 DSP in product development. I want to use high resolution on both edge of PWM. So I used HRPWM. But I getting some problem.

When I applied fraction part of duty to CMPAHR, then pulse width of channel B is also change (reduced). And pulse width of channel A is reduced instead of increasing.

Find attachment for more detail.

Regards,

HimanshuHRPWM in piccolo.pdf

  • 0
    TI__Expert 5940 points
    Hello,


    After looking at the code, my suggestion would be to disable TBCLKSYNC before configuring the ePWM/HRPWM modules and then to enable TBCLKSYNC after enabling HRPE. These steps are needed for using high resolution period. You can refer to Section 4.2.3.4.1 High-Resolution Period Configuration of the TRM for the full list of steps.

    Modify your code as shown below:

    SysCtrlRegs.PCLKCR0.bit.HRPWMENCLK = 1; // HRPWM
    SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 0; // Add this line of code here to disable TBCLK within the EPWM

    // Omitting code here

    (*ePWM[j]).HRPCTL.bit.HRPE = 1;
    SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 1; // Add this line of code here to enable TBCLK within the EPWM



    Elizabeth
  • 0 in reply to Elizabeth Joy
    Genius 4575 points
    Thanks for your kind attention.
    I done the same things that your suggested.
    But still problem is not solved. I get the PWM as same as mention in report.

    Regards,
    Himanshu
  • 0 in reply to Amtech
    TI__Mastermind 24095 points
    Hi,
    Changing CMPAHR value should not have any impact on the PWMB output.
    Regarding PWMA - I believe, you are seeing the correct behavior.
    From your configuration, it seems like you are set for symmetric mode of operation (Up-down mode). Changing CMPA or CMPAHR should result in a change of duty cycle in the same direction.
    Did you get a chance to evaluate any of the examples provided in controlSuite?
  • 0 in reply to Subrahmanya
    Genius 4575 points
    Hi,

    Yes, I am using Up-down mode. Let first discuss on ISSUSE-1 as mention in attachment.
    In which if I set
    Epwm1Regs.CMPA.half.CMPAHR = 0
    Epwm1Regs.CMPA.half.CMPA = 5

    (*ePWM[j]).HRCNFG.bit.EDGMODE = 2;
    (*ePWM[j]).HRPCTL.bit.TBPHSHRLOADE = 0;
    (*ePWM[j]).HRPCTL.bit.HRPE = 0;

    then PWM duty cycle is 0.111uSec. But if I change the setting as below then I got PWM duty cycle 0.123uSec instead of 0.111uSec.
    (*ePWM[j]).HRCNFG.bit.EDGMODE = 3; // control on both edge
    (*ePWM[j]).HRPCTL.bit.TBPHSHRLOADE = 1;
    (*ePWM[j]).HRPCTL.bit.HRPE = 1;

    Regards,
    Himanshu
  • 0 in reply to Amtech
    TI__Mastermind 24095 points

    Hi Himanshu,

    Can you try the following?
    - Start operation in certain mode of your choice
    - Enable AUTOCONV
    - Perform calibration using SFO
    - Change the values of CMPA, CMPAHR and observe the duty cycle changes.
    Let me know your observation.
    You could also refer to the controlSuite examples.


  • 0 in reply to Subrahmanya
    Genius 4575 points
    Hi,

    I am following same procedure to observe the duty cycle as you suggested. And I am also using SFO library and calling in background at every 1 sec. It gave 81 as Mep_scalefactor.

    Regards,
    Himanshu
  • 0 in reply to Amtech
    TI__Mastermind 24095 points
    Himanshu,

    MEP scale factor seems appropriate.
    My earlier question, when you set in one mode of operation - and change values of CMPA/HR what is your observation of the changes?
    Are they in expected line?
  • 0 in reply to Subrahmanya
    Genius 4575 points
    Hi,

    I already done that you said me. And I already shown the result in my attachment in ISSUE-2 and ISSUE-3. PWM width of channel A is changing as per the fraction part.

    Regards,
    Himanshu
  • 0 in reply to Amtech
    TI__Mastermind 24095 points
    Hi Himanshu,

    Thank you for the checks done.
    I'm unclear on why changing CMPAHR is having any effect on PWMB output.
    Is this occurring under particular condition ex:when you change from CMPAHR from Zero to Non-Zero value or so?
    Or does PWMB output change every time you change CMPAHR value?
    This is unexpected behavior. If so, i would like to debug this further.
    What is the hardware platform you are using?
    Is it possible to share the project - so that i can replicate the issue?
  • 0 in reply to Subrahmanya
    Genius 4575 points
    Hi,
    thanks for your kind attention.
    We developed our control board using TMS320F28069 and I am checking HRPWM with that board.
    Sorry to say but I can't share the project with you. But I already shared my initialization, settings of PWM with you in attachment.
    When I change CMPAHR from Zero to Non-Zero value, the PWMB output change. Then after it is remain constant for that CMPA value and any non-zero value of CMPAHR.

    Regards,
    Himanshu
  • 0 in reply to Subrahmanya
    Genius 4575 points
    Hi,
    Is there any update?

    Regards,
    Himanshu
  • 0 in reply to Amtech
    TI__Mastermind 24095 points

    Hi Himanshu,

    Tried replicating the issue with the configuration you provided - and did not observe any issue.
    There is no effect of CMPAHR on PWMB duty cycle.
    Are you able to consistently observe this or once in a while? Did you check on different parts and observe similar behavior?
    One more thing I suggest is can you check for this by disabling deadband? 

    -Bharathi.

  • 0 in reply to Subrahmanya
    Genius 4575 points

    hrpwm_mult_ch_prdupdown_sfo_v6.rarHi,

    As you suggested me to check with the example code. I checked with the “hrpwm_mult_ch_prdupdown_sfo_v6” of control suite. I attached the project for your reference. I made some changed as per my requirement. In this project also I observed the change in PWMB output. Please verified the attached project.

    Regards,

    Himanshu

  • 0 in reply to Subrahmanya
    Genius 4575 points
    Hi,
    Is there any update?

    Regards,
    Himanshu
  • 0 in reply to Amtech
    TI__Mastermind 24095 points
    Hi Himanshu,

    I got a chance to experiment with the code you sent. I did not observe any issues with PWMB duty cycle.
    Did you see this behavior on all EPWMs? Also, how is this affecting your application - i just wanted to understand if there is any other source causing this behavior on your board/application.

    -Bharathi.
  • 0 in reply to Subrahmanya
    Genius 4575 points
    Hi,
    Thanks for verifying my code.
    Can you share the waveform of EPWM1A and EPWM1B with
    Epwm1Regs.CMPA.half.CMPA = 5
    and different value of CMPAHR.

    Regards,
    Himanshu
  • 0 in reply to Subrahmanya
    Genius 4575 points
    Hi,

    Waiting for your response.

    Regards,
    Himanshu
  • 0 in reply to Amtech
    Genius 4575 points
    Hi,

    Waiting for the waveform of EPWM1A and EPWM1B with
    Epwm1Regs.CMPA.half.CMPA = 5
    and different value of CMPAHR.

    Regards,
    Himanshu
  • 0 in reply to Subrahmanya
    Genius 4575 points
    Hi,

    Waiting for your response.

    Regards,
    Himanshu
  • 0 in reply to Amtech
    TI__Mastermind 24095 points
    Hi,

    As mentioned earlier - I did not observe any issues with PWMB duty cycle.
    To debug your issue further, it would be good if we can trace the source of the problem - and hence the question earlier.
    "Did you see this behavior on all EPWMs? Also, how is this affecting your application - i just wanted to understand if there is any other source causing this behavior on your board/application."

    -Bharathi.