Start 2 timers in 1 instructions? (nRF52)

RE: Start 2 timers in 1 instructions? (nRF52)

Cedric Honnet — Tue, 22 May 2018 09:40:07 GMT

Update:

For those interested, the chosen solution was to start the timers and reset them together using PPI and forks.

The code is available on this repo:

https://github.com/HiveTracker/PPI

...and which was mostly developed to be used here:

https://github.com/HiveTracker/firmware

RE: Start 2 timers in 1 instructions? (nRF52)

Rune Holmgren — Fri, 06 Apr 2018 14:59:44 GMT

The Event Generator Unit is exactly what you are looking for.

Best regards,
Rune Holmgren

RE: Start 2 timers in 1 instructions? (nRF52)

Cedric Honnet — Thu, 05 Apr 2018 12:22:05 GMT

OK, thanks anyway ;)
Last question if I may: is there a way to trigger these tasks manually? (a bit like a software event)

RE: Start 2 timers in 1 instructions? (nRF52)

Rune Holmgren — Thu, 05 Apr 2018 10:53:24 GMT

Sorry, it doesn't seem like we have any examples which use FORK. You will have to make due with the PPI documentation, but as far as I can tell FORK is pretty straightforward so I think you will be fine.

Best regards,
Rune Holmgren

RE: Start 2 timers in 1 instructions? (nRF52)

Cedric Honnet — Thu, 05 Apr 2018 09:17:09 GMT

Sorry, PPI is OK, I was asking if you had FORK examples ;)

Thanks again!

RE: Start 2 timers in 1 instructions? (nRF52)

Rune Holmgren — Thu, 05 Apr 2018 07:45:20 GMT

In the nRF5 SDK you can find a reasonably simple PPI example in the folder "nRF5_SDK_15.0.0_a53641a/examples/peripheral/ppi". That is a good starting point to see an implementation utilizing PPI if you haven't seen it already. Other than that you can search in the SDK and find other examples using PPI to see "real" applications using it.

Hoping that may be of help.

Best regards,
Rune Holmgren

RE: Start 2 timers in 1 instructions? (nRF52)

Cedric Honnet — Wed, 04 Apr 2018 16:09:38 GMT

Thanks a lot, Rune!

I've been playing a bit with PPI and the fork feature was actually my next exploration plan.

My current test uses PPI in a fairly simple way:

https://github.com/HiveTracker/ppi_test/blob/master/PPI.cpp#L61-L86

...and it's using Nordic's lib, so I guess I could use the fork wrapper too:

https://github.com/HiveTracker/ppi_test/blob/master/nRF_SDK/nrf_ppi.h#L234-L265

Is there any easy example that you would recommend to understand its use better?

Thanks again ;)

RE: Start 2 timers in 1 instructions? (nRF52)

Rune Holmgren — Wed, 04 Apr 2018 15:53:29 GMT

Hi,

The first idea using PPI seems like the best way to do this. PPI supports a feature called "FORK" which enable you to cause a single event to start two timers. This will allow you to start both of the timers at the same time and not end up with a one CPU clock cycle offset.

While PPI may seem a bit complicated it often turns out to be the far simplest solution when you need precise concurrency. (It's also very low power compared to using the CPU)

Best regards,
Rune Holmgren