CCS/TMS320F28379D: how to make EPWM1 as a slave

Manikanta Pallantla

Tool/software: Code Composer Studio

Please clarify the following questions.

1. Can we make the EPWM 1 as a slave. All the examples given in the references use EPWM1 as master and subsequent EPWMs as a slave.

2. My application requires EPWM1,2,3 acts as a slave so that TBCTR will be reset to the value given TBPHS register when the SWFSYNC is enabled. For this I have written code as below.

For making EPWM 1 as a slave:

Above code is not generating the correct duty ratio. However when the EPwm1Regs.TBCTL.bit.PHSEN is disabled, expected duty ratio is being generated. Can some one tell me why it is happening? What changes do I need to make so that It would give the correct duty ratio and also acts as a slave?

For example: Lets say EPWM1 set as master and EPWM2 and 3 set as a slave with 120 degrees and 240 degrees phase shift respectively.

And EPWM2 sync In is same as Sync Out of EPWM1 (this case same as SyncIn of the EPWM1 ) and EPWM3 sync In is same as Sync Out of EPWM2 as shown below.

In this configuration,

As soon as EPwm1Regs.TBCTL.bit.SWFSYNC is enabled, will the EPWM1 TBCTR set to zero even though PHSEN of EPWM1 is disabled?

I know that as soon as EPwm1Regs.TBCTL.bit.SWFSYNC is enabled, EPWM2 and EPWM3 TBCTR will be set to PHase register values. I would like to know what happens to TBCTR value for EPWM1.

Thanks for your time.

Regards

Manikanta P

over 5 years ago

0 Nima Eskandari over 5 years ago

TI__Guru 52220 points

did you take care of the INPUT XBAR? You have to make sure INPUT 5/6 are not connected to GPIO0/1 or any other GPIO you are using.

Nima

0 Manikanta Pallantla over 5 years ago in reply to Nima Eskandari

Prodigy 120 points

Dear Nima,

Thanks for your response. I will check and get back to you.

Regards

Manikanta P

0 Manikanta Pallantla over 5 years ago in reply to Nima Eskandari

Prodigy 120 points

Hi Nima,

I could find that Input 5 and Input 6 are not connected to any GPIOs.

In the above screen shot, I can observe that those functions haven't been called at all throughout the project. So I am still not sure why the duty ratio is still wrong from EPWM1 after enabling the PHSEN. Could you please help me with this. Thanks.

0 Nima Eskandari over 5 years ago in reply to Manikanta Pallantla

TI__Guru 52220 points

For this device it means they are conntected to GPIO0... Thats is not good. Make sure to change them to a GPIO you are not using...

0 Manikanta Pallantla over 5 years ago in reply to Nima Eskandari

Prodigy 120 points

I have to use the EPWM1 as it is connected to the gate drive in the layout. So Do you think there is no way to make EPWM1 as a slave?

0 Nima Eskandari over 5 years ago in reply to Manikanta Pallantla

TI__Guru 52220 points

The source for INPUT XBAR is GPIO0 by default, so when EPWM1 is in slave mode, then if you have a signal on GPIO0, it will keep syncing itself. You need to change those INPUT XBAR sources to another GPIO.

Nima

0 Manikanta Pallantla over 5 years ago in reply to Nima Eskandari

Prodigy 120 points

I have just seen that INPUT5SELECT is connected to GPIO0 by default. I think it should work now if I change to a different GPIO. Thanks a lot for your help. I really appreciate it.

0 Nima Eskandari over 5 years ago in reply to Manikanta Pallantla

TI__Guru 52220 points

Perfect, make sure to press the GREEN VERIFIED ANSWER button.

0 Manikanta Pallantla over 5 years ago in reply to Nima Eskandari

Prodigy 120 points

Hi Nima,

Changing the GPIO, solved the issue. I have one last question to ask.

I know that enabling the signal EPWM1Regs.TBCTL.bit.SWFSYNC will initialize the TBCTR with TBPHS register value. Is there any way we can verify through the oscilloscope? I can observe the TBCTR value in the watch window. I would like to know other ways of seeing this. Thanks once again.

0 Nima Eskandari over 5 years ago in reply to Manikanta Pallantla

TI__Guru 52220 points

View the TBCTR in oscilloscope?

0 Manikanta Pallantla over 5 years ago in reply to Nima Eskandari

Prodigy 120 points

No, I want to see the effect of the EPWM1Regs.TBCTL.bit.SWFSYNC on the EPWM1A PWM signal in real-time (Oscilloscope).

0 Nima Eskandari over 5 years ago in reply to Manikanta Pallantla

TI__Guru 52220 points

well, toggle a GPIO when you set the SWFSYNC register, then view the EPWM output on oscope to see the width of your EPWM signal.

Nima

0 Manikanta Pallantla over 5 years ago in reply to Nima Eskandari

Prodigy 120 points

Okay. Thanks a lot for your quick responses.

Regards

Manikanta P

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CCS/TMS320F28379D: how to make EPWM1 as a slave