Relation RTC1 Compare / app_timer

[Franz]

Hi,

I'm using a nrf52810 on with SDK V15.2 with SD112.

The application uses the app timer and also TIMER1 for other purposes (and TIMER0 is locked by Softdevice).

What I essentially need is RTC1 to periodically trigger a SAADC sample event without interfering with the app_timer library. (I currently do the sampling using the app_timer, but the desired sample rate is not possible with app_timer (below 1ms) and TIMER1 is already used for another purpose)

Now, the accepted answer in this post (Can I use RTC1?)  - although for den nrf51 -suggests that since app_timer library only uses the COMPARE[0] event of the RTC1, so compare registers 1-3 should be open, right?

Two questions:

1.) Is it possible to e.g. use the COMPARE3 of RTC1 to periodically trigger a SAMPLE Task via PPI WIHOUT INTERFERING the app_timer running on RTC1?

2.) If yes, how would i do so? I see that i have to always reload the CC Values each time a COMPARE match has happened (for whatever reason). How can I do that when using PPI (and without starting to modify the timer_app library (because RTC1 IRQ is implemented in that library)?

Thanks a lot,

Franz

[Susheel Nuguru]

Hi

1. Theoretically yes, you can use it. But I would not recommend it as the behavior of the app_timer would change. Which chip revision are you using? can't you just use RTC2 instance for this?
2. Please see above, I do not thinking using another CC register of RTC1(app_timer) will fulfill your purpose of periodical trigger of SAADC sample without interfering with app_timer. Using another CC channel in RTC1 would still cause RTC1 interrupts confusing the app_timer a lot.

[Franz]

Hi Susheel,

Ok - that´s what I feared.. well I would have to look for the specific revision ID of the chip, but as far as I can see form the datasheet, the nRF52810 only has RTC0 and RTC1, right? (I think only nRF52832 and upwards have RTC2)

Kind regards,

Franz

[Susheel Nuguru]

Yes you are correct, nRF52810 has only two instances of RTC. I see your dilemma now.

You might have to upgrade to nRF52832 for that. You idea then using the PPI to connect the timer events to trigger SAADC samples sounds easy then.