TMS320F28335: Synchronizing the pwm outputs from two different controllers

Akhil,

I think this would work with most uses of the PWM. You will need to synchronize the two devices together, to do that one will need to be a "Master" and one will be a "Slave". Are you doing anything that requires repeated sync pulses like phase shifting?

Regards,
Cody 

Hello Cody,

Yeah, This would sync the PWM outputs. We basically have two controllers with the exact same code and I would like to match the clocks of both the DSPs, Is it possible by any chance to sync the clock pulses? We're using external oscillators.


Thank you,
Akhil

Akhil,
Do you still need help with this issue?

Regards,
Cody

Hello cody,

First of all, sorry for such a long delay. I think that the shared clock can only be used if both the controllers are on the same PCB and i guess it should be very close to the clock. In our thing, since it is a redundant design, we have two separate PCBs and i think we won't be able to share the same clock because the PCBs are separate and if the clock fails both the controller won't work. Is there any other way? Can it be done in software through any means? like using an other hardware to synchronize the pulses?

Thank you,
Akhil Pillai

Hi Akhil,

The best option here would be to use the external syncout from the master PWM of device # 1 to sync the master PWM of device # 2. If one of the devices fails the other would continue generating correct PWMs. This won't add any software overhead.

Hrishi

Hi Hrishi,

How to obtain the external syncout from device#1? It seems impossible to use GPIO to output it.

Regards
Kerui

Hi Kerui,

For the F28335 device EPWMSYNCO signal can be brought out on GPIO6 and GPIO33. Please refer to the following 

 

Make sure to configure the PWM module to generate this external sync.

Hrishi

Hi Hrishi,

What you suggested is for syncing the PWM output but I need to sync the clock of the processors not only the PWM outputs.


Thanks,
Akhil

Akhil,

Ohh that is a completely different problem. I believe this should be addressed/guaranteed outside of the device. 

Have you looked at clocking the two devices using an external clock?

Hrishi

Hello,

Yeah I did, but using a shared clock for both the controllers would not be redundant design. I mean it would be a single point failure. I'll look around if some hardware is available to sync the clocks, meanwhile, if you have any other suggestions, please do let me know.



With Warm Regards,
Akhil Pillai