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PWM Signals Not Synced

Louis Zhu
Expert 1685 points

Other Parts Discussed in Thread: CONTROLSUITE

I ran the example code epwm_real-time_interrupts project from controlSuite on F28069 controlStick, and noticed that PCLKCR0[TBSYNC] was disabled before the initialization of ePWM1 and ePWM2, and enabled after the initialization. However, the two PWM waveforms show that the rising edge on the two waveforms are NOT aligned. Please refer to the screenshot attached.

If that's normal, what does the TBSYNC try to achieve?

Please advise.

tek00000.tif
  • 0
    Guru 192875 points

    HI,

    TBSYNC: 

     

    Time-base synchronization input (EPWMxSYNCI) and output (EPWMxSYNCO) signals.
    The synchronization signals daisy chain the ePWM modules together. Each module can be configured
    to either use or ignore its synchronization input. The clock synchronization input and output signal are
    brought out to pins only for ePWM1 (ePWM module #1). The synchronization output for ePWM1
    (EPWM1SYNCO) is also connected to the SYNCI of the first enhanced capture module (eCAP1).

    You can check out: SPRUH18D for more info. Also check by setting same period to both the PWMs and revert.

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Expert 1685 points

    Gautam,

    I was perplexed by the info in section 3.2.2.3.2 in the same document. It states that

    When set, all enabled ePWM module clocks are started with the first rising edge of TBCLK aligned.

    but my waveforms show that they were not aligned.

    I need a clarification on that aspect.

  • 0 in reply to Louis Zhu
    Guru 192875 points

    Hi,

    Please check with the DSO's trigger settings, also please check with the code and eliminate any delays if present between generation of two or more pwms.

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Expert 1685 points

    I've verified that TBCLKSYNC makes difference on PWM edge alignment.

    Thanks for your inspiration.

  • 0 in reply to Louis Zhu
    Guru 192875 points

    You're Welcome, Louis.

    Congrats and Cheers,

    Gautam