BLE Mesh App_timer stops after few minutes of work

[luciom]

Hello
I've noted some problems when try to use the app_timer in repeat mode with a tick time <= 100ms.
I see that the BLE Mesh SDK sets the RTC1.CC[0] compare register in order to achieve the minor "tick time" among all app timers running instances.
With such compare time, i've found that after few minutes, the RTC1.CC[0] compare register stops, while the RCT.COUNTER is still running.
So, the RTC1.EVENTS_COMPARE[0] flag is not setted and consequently all the app timers aren't updated inside RTC1_IRQHandler.
The RTC1.CC[0] compare register restarts when the RTC.COUNTER register return to the same value of the RTC1.CC[0] register had when it stop.

I'm using the nRF5_SDK_15.2.0 and the SDKforMeshv300 with s140_nrf52_6.1.1_softdevice

Please help.

[Andrea Pieretti]

Hi, I'm a Lucio's co-worker.
I' think that the issue is about interrupt priorities after the mesh_stack_start() call.

I've instantiated an 10ms tick app_timer in repeat mode and I've monitored it with a spy pin inside timer tick handler.
As you can see in the attached picture, the 10ms tick is jittering and there are many "holes": maybe the system is busy with another higher priority task.

After few minutes, all the app_timer instances stop working.

Please help. We are in prodution!

[Andrea Pieretti]

Maybe I've found a trick to make app timer to work consistently: I stop the app_timer at the start of its own tick handler and restart it and the tick handler's end.

Is this a correct solution for our problem?
(I'm using app_timer_mesh)

[Mttrinh]

Hi,

I think it should be fine to do it that way, but could you also try using our latest SDK v3.1.0 and see if the the issue is still there before doing it this way?

[Andrea Pieretti]

Hi,

the workaround seems to work in SDK v3.1.0. In SDK v3.0.0 it doesn't work.

however, the SDK v3.1.0 has some problems regarding messages retransmission as my co-worker Lucio told in this ticket https://devzone.nordicsemi.com/f/nordic-q-a/42802/ble-mesh-app_timer-stops-after-few-minutes-of-work.
So, it seems that we've an SDK with app_timer issues and the other one with retransmission issues. Which one is more reliable?

[Mttrinh]

Hi,

I assume you meant this ticket: https://devzone.nordicsemi.com/f/nordic-q-a/42981/mesh-sdk-3-1-0-retransmit-count-error. The bug mentioned in that ticket have been reported, so I suggest you to use our latest Mesh SDK v3.1.0.