AM2634: Multicore syncing

Hi Sue, 

Should be possible to get this much closer and totally deterministic on every startup. I'll research and get back to you. I probably won't be able to look at this until early next week though. 

Thank you,

-Randy

Sure. Thank you. I will wait for your response.

Just a heads up I'll be looking at this tomorrow. 

Thank you,

-Randy

Hi Randy, checking if you have any update?

Hi Sue, 

EPWM module synchronization is handled at the module level using the time-base (TB) submodule. If you check out the AM263x TRM, you can find info on this in 7.4.5.4 Time-Base (TB) Submodule. 

Just excerpting some of the critical sections from the TRM below. What we need to do is select the correct EPWMSYNCINSEL value to synchronize the selected EWPM to one of the available sync sources and then setup a sync output to feed that. The Figure 7-114 diagram shows some of these, but the options are extensive. Check out Table 7-105. EPWM SYNC Selection for all of the available options. Each EPWM module has these same options. If you want one EPWM sync output to master other EPWM, you also need to setup the corresponding EPWMSYNCOUTEN bits - see Figure 7-114. 

To confirm: In your case, you are needing one R5F core to drive the duty cycle on one EPWM, and another R5F core to drive the PWM duty cycle on another EPWM, but need both EPWM to be synchronized, correct? 

I think the IPC notify API you are using will keep these R5F cores relatively synchronized when writing out these EPWM register updates. You could setup a EPWMx syncout -> EWPMy syncin scheme. Or you could use one of the other sync sources to sync both EPWM modules from another location. The simplest system might be using the Software Forced Synchronization Pulse. I will give that method a try. 

Let me know if that helps. I'll let you know what else I find. 

Thank you,

-Randy

Hi Sue, 

Actually, this example on e2e might be a good starting point for you as well: https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1160182/mcu-plus-sdk-am263x-am263x---is-there-an-example-project-present-to-show-how-to-configure-two-pwm-channels-in-phase-shift-mode

I started extending the HR DUTY CYCLE example in the SDK to include another EPWM module and open up the synchronization sources: https://software-dl.ti.com/mcu-plus-sdk/esd/AM263X/08_06_00_34/exports/docs/api_guide_am263x/EXAMPLES_DRIVERS_EPWM_HR_DUTY_CYCLE.html

The above example does this. I changed it to run on the LP-AM263 LaunchPad with SYSCONFIG CONFIG_EPWM0 mapped to EPWM9 and CONFIG_EPWM1 mapped to EPWM13. Rebuilt and ran it just fine. 

For your specific application, I think you could start with the same setup. Let me know if this works for you. 

Thank you,

-Randy

Thank you, Randy. I will try your suggestions. 

Hi Sue, 

Let me know if that ends up resolving the issue for you. Phase synchronization for the EPWM should not require any CPU intervention, just setup of those syncout/syncin paths. 

One other thing: When I was looking around ti.com I found these EPWM peripheral introductions/tutorials on the C2000 processors support pages: 

https://www.ti.com/video/series/C2000-enhanced-pulse-width-modulator.html 

Our AM263x MCU use the same EPWM peripherals (see the TRM), so many of the concepts are applicable to AM263x as well. These should serve as a good introduction to many features, including the synchronization output/input paths available. See the TRM and SYSCONFIG for specifics for AM263x. 

Thank you,

-Randy

Hi Randy,
The EPWM syncin/syncout worked for me. Thanks again for your inputs.