CCS/TMS320F28335: count direction of epwm

user5137167

Part Number: TMS320F28335

Tool/software: Code Composer Studio

Hi,

About epwm module of 28335, we have a problem.

The epwm counter mode of 28335 is configured as increment and decrement. And we need to set the initial value and count direction. How to make counter decrement at first, and then increment?

Thanks!

over 5 years ago

0 Marlyn Rosales Castaneda20 over 5 years ago

TI__Mastermind 25800 points

Hello,

The time-base counter of the epwm module only has three distinct modes of operation: up-down count, up-count, down-count.

Can you please explain what kind of output you hoping to achieve?

I would suggest referencing the 'Action-Qualifier' and 'Dead-Band' submodules of the epwm in the Technical Reference Manual

Best Regards,

Marlyn

0 Cody Watkins over 5 years ago

TI__Mastermind 42195 points

user5137167,

the counter direction bit (TBSTS.CTRDIR) is read only, you cannot write it.

One thing that may work for you.

Configure the PWM, but do not connect the GPIO buffer to the PWM
Setup the CTR=PRD ISR to enable the GPIO buffer

This should delay your PWM output until the PWM is counting down. This may work for your system, if not, please explain your issue and we will help working through setting up the C2000 for your system.

PS it may be easier to reverse your CxD and CxU actions, this will apply a 180 degree phase shift and make the "count-up" portion of the PWM period look like the "count-down" portion.

Regards,
Cody

0 user5137167 over 5 years ago in reply to Cody Watkins

Prodigy 70 points

It may work.

How about TBCTL[PHSDIR]=0? Does it work?

0 user5137167 over 5 years ago in reply to Marlyn Rosales Castaneda20

Prodigy 70 points

0 Cody Watkins over 5 years ago in reply to user5137167

TI__Mastermind 42195 points

You actually bring up a good idea with setting TBCTL.PHSDIR = 0. This will affect the behavior after a sync event. So it should be easy enough to use the SW force sync and then enable the outputs. Alternatively you could do something like I described above where you connect the GPIO buffer to the PWM in the ISR that is triggered by a sync event.

Regards,
Cody

0 user5137167 over 5 years ago in reply to Cody Watkins

Prodigy 70 points

Thanks!

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CCS/TMS320F28335: count direction of epwm