Start 2 timers in 1 instructions? (nRF52)

[Cedric Honnet]

Hi all!

TL;DR

Is there a way to start 2 timers in 1 instructions? (or to synchronize them afterward?)

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Background

I need to take 8 timestamps of GPIO edges using PPI events/tasks (more explanations here).

This needs 2 timers as they don't have more than 4 (or 6) capture registers each.

To have coherent timestamps, the timers should start simultaneously, and I'm looking for a good way to do it.

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1st idea

It seems unlikely that a simultaneous start is possible as they have different register addresses, ex:

TIMER1: 0x40009000 

TIMER2: 0x4000A000

But as they are running at 16MHz and the core runs at 64MHz, it might not be impossible that the 2 start request happen simultaneously:

nrf_timer_task_trigger(NRF_TIMER1, NRF_TIMER_TASK_START);
nrf_timer_task_trigger(NRF_TIMER2, NRF_TIMER_TASK_START);

Should I use a PPI event to reset both timers in the same time? (it seems complicated but maybe the most appropriate)

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2nd idea

Maybe there's a reliable way to check that the 2 timers are synchronized, and if not, copy the value of one in the other?

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Does anyone have any suggestion?

Thanks a lot!

Cedric ;)

[Cedric Honnet]

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