How to use WFE reliably?

RE: How to use WFE reliably?

pungent1188 — Wed, 15 Nov 2023 12:39:35 GMT

Well it happen to me, fast wakeup came from LIN device and bricked my product until power cycling.

RE: How to use WFE reliably?

gnf — Tue, 12 Sep 2017 09:32:50 GMT

The link to the example is dead: github.com/.../main.c

Maybe this is linking to the same file: github.com/.../main.c

RE: How to use WFE reliably?

RK — Thu, 20 Nov 2014 00:51:34 GMT

Yes your code has a race condition in it, it's possible for the interrupt to arrive between your test and the WFE. Unlikely, but possible.

Setting SEVONPEND will cause the the event flag to be set every time there's a pending interrupt, and WFE doesn't sleep if the event flag is set. That should do what you want.

I've found every time I looked into this that, despite the vast amount of documentation ARM writes about WFI and WFE, it's very hard to find definitive answers to questions about exactly, precisely in all instances when the event flag is set .. and the books on Cortex tend to skate over it too.

RE: How to use WFE reliably?

Quax64 — Wed, 19 Nov 2014 12:13:24 GMT

Thanks, but these examples do not answer my question. I have __wfe() working already, but I need to verify that the CPU is reliably waking up again, even under very rare circumstances.

RE: How to use WFE reliably?

Quax64 — Wed, 19 Nov 2014 12:08:04 GMT

For the time being, I would like to keep my code as simple as possible and rather not hide fundamental problems under another software layer. As far as I understand, sd_app_evt_wait() is anyway part of the SoftDevice which I don't use.

RE: How to use WFE reliably?

Stefan Birnir Sverrisson — Wed, 19 Nov 2014 12:05:16 GMT

If you are using softdevice, use the sd_app_evt_wait(). If you are not using softdevice, use the __WFE() as done in this example

The __WFE() is also discussed on this thread.

RE: How to use WFE reliably?

Ulrich Myhre — Wed, 19 Nov 2014 11:34:00 GMT

Have you had a look at sd_app_evt_wait() in nrf_soc?