TMS320F28069: Changing PWM period on a phase-shifted PWM modules

Lev Avdejev

Hello,

I have a requirement to change PWM frequency during run-time. To achieve this I write a new value into period register (TBPRD) in an interrupt service routine achieve the new frequency. Shadow mode is enabled so the new value is first buffered and written to the active register on the next period.

The functionality works perfectly for a single PWM module, which does not have phase-shift enabled.

Is it possible to change PWM frequency of 3 PWM modules, which have phase-shift enabled and are shifted between each other?
Could you please explain how to do it correctly?

Using similar approach as for PWM without phase-shift did not bring required result.

Thanks!

over 6 years ago

0 Cody Watkins over 6 years ago

TI__Mastermind 42195 points

Lev,

It should be as simple as updated the TBPRD register for all ePWMs at the same time. It NEEDS to happen in the same PWM cycle to ensure your PWMs aren't out of sync for a cycle.

One way to implement this is to define a "safe window" where you know the device has enough time to update all PWM frequencies. There are many ways to do this, but here is simple way to correct the problem that i think you are having.

https://e2e.ti.com/support/microcontrollers/c2000/f/171/t/873702

Regards,
Cody

0 Lev Avdejev over 6 years ago in reply to Cody Watkins

Intellectual 260 points

Hello Cody,

Thank you for valuable instructions.

Regards,
Lev

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TMS320F28069: Changing PWM period on a phase-shifted PWM modules