How to sync CPU TIMERx and EPWMx

ENVER CANDAN

Is there a way to sync CPU timer (lets say 0) and epwm (lets say 1a) in piccolo f28069?

They both sourced from sysclock but I couldn't figure out how to sync them.

I set up epwm1 and cpu timer 0 interrupt and then toggle a gpio pin at cpu timer 0 interrupt. When I observe the waveforms in scope, the one that I trigger, just moves around and this makes me think that they are not synced.

Basically, what I want to to is I want to have an interrupt that is 10 times smaller than epwm freq.

Any ideas?

over 11 years ago

0 Igor Gorbachev over 11 years ago

Guru 20525 points

Hi Enver,

perhaps this thread will be useful http://e2e.ti.com/support/microcontrollers/c2000/f/171/p/270236/944737.aspx#944737

Regards,

Igor

0 ENVER CANDAN over 11 years ago in reply to Igor Gorbachev

Prodigy 60 points

Hi Igor, thanks for your quick response, I followed the thread but I couldn't relate it with my problem.

I need to have the CPU TIMER to generate interrupts that are synced with epwm signals. I have tried it and to verify that it works; I toggle a GPIO bit in the cpu timer interrupt and scope it. I scope epwm signal too but they are not synced. if i trigger scope for epwm signal, toggle bit moves around. if i trigger toggle bit, epwm signal moves around.

Maybe I am not following the correct path to generate what I need. My expected waveform is like the following; here epwm freq is 200kHz and the interrupt happens at 20kHz and toggles and they are synced.

0 Igor Gorbachev over 11 years ago in reply to ENVER CANDAN

Guru 20525 points

Hi, Enver.

Would you like to use another ePWM channel for 20 kHz instead timer like this thread http://e2e.ti.com/support/microcontrollers/c2000/f/171/t/237767.aspx

Regards,

Igor

0 Bill Finger over 11 years ago in reply to ENVER CANDAN

Genius 3735 points

Couldn't you just use the PWM interrupt, and simply discard 9 out of 10 of them?

Another alternative: use DMA. This takes some effort, but you can have the DMA controller interrupt every 10 PWM events. Just set it up to do a dummy copy somewhere, and interrupt when the block of 10 words is complete.

0 ENVER CANDAN over 11 years ago in reply to Bill Finger

Prodigy 60 points

Hi Igor and Bill, thanks for your responses.

I didn't want to sacrifice one pwm channel for that, that's why I was looking for alternative ways. I think there is no way to sync cpu timer and epwm channels.

Thanks again for your time.

Enver

0 Igor Gorbachev over 11 years ago in reply to ENVER CANDAN

Guru 20525 points

Enver,

as variant without using timer but with using external interrupt:

200 kHz ePWM -> XINT1 from GPIO input -> ISR with count to 10 ->GPIO out ->XINT2 (20 kHz) from GPIO input

it seems thus you will get external interrupt XINT2 with frequency 20 kHz with sinchronization from 200 kHz.

Regards,

Igor

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How to sync CPU TIMERx and EPWMx