EVMK2G: EDMA triggered by EPWM

Hi Benito,

Our RTOS expert is out of office this week. Please expect delayed response.

Dear mr. Bin Liu,

thank you for your answer.

I'll wait for the expert to return. 

A little clarification: my code is bare-metal; I programs the device through the CSL library functions. 

I do not know how to connect the EDMA channels with the signals SOCA/B within the EPWMx module.

Indeed, in my current code version the PWM sets the signals SOCA/B but this event does not trigger the proper bit in the event register of EDMA module.

There is no mention of SOCA/B within the section 10.2.1 of the TRM SPRUHY8I.

According the following post: 

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/997683/66ak2g12-epwm-hrctl-register?tisearch=e2e-sitesearch&keymatch=epwm%2520edma#

It seems that is possible to trigger the EDMA by means of SOCA/B signals of the EPWMx (as I succesfully did on TMS320F2807x). 

I'll wait for a feedback from this forum.

Thank you for the support.

Benito Carotenuto

Hello Benito Carotenuto,

In the thread you referenced, I believe EPWM is configured to generate an interrupt based on SOCA and the interrupt triggers EDMA:

• EPWM_ETSEL Register = 0x900: Enable SOCA pulse, Enable event time-base counter equal to zero
• EPWM_ETPS Register = 0x500: Generate an interrupt on the first event INTCNT = 01, ePWM Interrupt Event (EPWMx_INT) Counter Register = 1

Regards,

Jianzhong

Dear mr. Jianzhong Xu,

thank you for your feedback.

The registers you mentioned enable the generation of SOCA/B signals in EPWM module.

How can I connect the EDMA channels to this signals?

In accordance with the table 10-8 of TRM SPRUHY8I, the EDMA channels 32-37 are associated only to the EPWM_x_INT. 

There is no mention of the signals SOCA/B within this sync events list.

For example, what is the number of the channel that is triggered by the signal EPWM1_SOCA ?

Thank you,

Benito

Dear experts,

any news about my question?

Waiting for a your feedback,

Best regards.

Benito

Dear James,

thank you for your feedback.

JJD said:

You will have to setup the EPWM module to produce interrupts when SOC events occur.

I understand that the signal EPWMX_SOCA/B can not directly trigger the EDMA channels because of the layout of the SOC. Hence,  it is necessary to produce the EPWM interrupts.

According Table 11-909 of TRM,  an important difference between the EPWMx_INT and EPWMx_SOCA/B is the flag bit. 

The EPWMx_SOCA/B output will continue to pulse even if the flag bit in EPWM_ETFLAG is set.

The EPWMx_INT output instead set the flag bit to 1 and no further interrupts will be generated until the flag bit is cleared. Up to one interrupt can be pending while the EPWM_ETFLG[0] INT bit is still set. If an interrupt is pending, it will not be generated until after the EPWM_ETFLG[0] INT bit is cleared.

Consequently, every time the interrupt triggers the EDMA, the DSP must clear the bit EPWM_ETFLAG[0] by means of  register EPWM_ETCLR[0] in order to allow the next interrupt generation.

Therefore, the EPWM module can not trigger the EDMA without the intervention of DSP. Afterwards each transfer from L2SRAM to CMPA/B, the DSP must clear the ETFLAG[0]...

For my work I want to use the capability of the module EDMA to continuously copy values from L2SRAM to the EPWMx_CMPA/B registers without the intervention of DSP.

Unlike the Piccolo (TMS320F2807x), this is not possible with EVMK2G. 

Is my comprehension right?

Thank you.

Best regards,

Benito