Add ETM support for general purpose timers

[sisoteuz]

Implement Event Task Matrix functions for general purpose timers. ETM is only available for esp32-c6 and esp32-h2 chips.

Closes #1274

Must

• The code compiles without errors or warnings.
• All examples work.
• cargo fmt was run.
• Your changes were added to the CHANGELOG.md in the proper section.
• You updated existing examples or added examples (if applicable).
• Added examples are checked in CI

Nice to have

• You add a description of your work to this PR.
• You added proper docs for your newly added features and code.

[sisoteuz]

I will explore using macros to generate code for each timer instead of introducing this const G: u8 parameter on the different traits like I did in this draft.

[bjoernQ]

Thanks for working on this!

I'd say introducing the const generic is something we'd like to avoid.

One solution might be to add a function like fn id() -> u8; to the TimerGroupInstance trait and implement the function for TIMG0/TIMG1 to return 0 or 1. The compiler should optimize all that away so it won't introduce runtime cost

Not sure if that's expected (since it's a draft PR) but the example doesn't work for me, yet.

[sisoteuz]

One solution might be to add a function like fn id() -> u8; to the TimerGroupInstance trait and implement the function for TIMG0/TIMG1 to return 0 or 1. The compiler should optimize all that away so it won't introduce runtime cost

I actually started with doing that and ditching it because I was aiming to introduce no extra runtime cost. But seems it’s fine so I’ll definitely give it a go. Thanks for the suggestion !

Not sure if that's expected (since it's a draft PR) but the example doesn't work for me, yet.

I will double check as I tested late last night on my dev board, might very well be that I missed to push something.

[sisoteuz]

I can confirm that the implementation is working on my esp32-c6 board with the example etm_timer.rs. The example sets up ETM channel 0 to stop Timer0 on alarm that we configure to trigger after 100ms the counter starts.

The output is as below :

counter in interrupt: 10    # Alarm triggered the interrupt after 100ms and reset the counter (default behaviour)
counter in main: 10         # Counter got stopped by ETM (new feature)
counter in main: 10
counter in main: 10
counter in main: 10
counter in main: 10
counter in main: 10

I couldn't test on esp32-h2 as I don't own one. However looking at the technical reference document the ETM tasks and events IDs are the same so in theory it should work.

Now 2 checks are failing apparently because of the use of delay.delay_ms(500u32) in my example and not importing the DelayMs trait (I don't see why that would be necessary).

I can successfully build all the examples locally and I'm using Delay like in all the other examples. Really not sure why it is failing, I'd really appreciate any help as this failure doesn't make a lot of sense to me.

Thanks.

[bjoernQ]

I tested on ESP32-H2 and it works

For the delay: there were some changes lately - probably easiest would be to use delay_millis instead of delay_ms

Otherwise looks good to me

[sisoteuz]

For the delay: there were some changes lately - probably easiest would be to use delay_millis instead of delay_ms

Thanks that fixed the issue. I moved the PR to ready for review.

[jessebraham]

Thanks for the contribution, this LGTM!

@bjoernQ is more familiar with this particular peripheral, so I will wait for him to give this his stamp of approval as well.

[sisoteuz]

Thanks ! I had a blast making this contribution.

[bjoernQ]

LGTM - Thanks for your contribution!