NRF54L15 Timer interrupt not generating after few cycles

RE: NRF54L15 Timer interrupt not generating after few cycles

darav — Mon, 30 Mar 2026 14:02:38 GMT

yes, we do have a log static that "k_timer()" is actually called which is observed even when the issue is produced.
Sure, i'll try my application with v3.2.4 and update you on it

I think this is the issue/bug we are observing -:
https://github.com/zephyrproject-rtos/zephyr/pull/91432
github.com/.../89147

RE: NRF54L15 Timer interrupt not generating after few cycles

Vidar Berg — Fri, 27 Mar 2026 15:35:24 GMT

Thanks for confirming.

[quote user="darav"]Due to this implementation logically, if the timer is working properly ticks variable will be greater than 1 and the if condition will be true which will keep on feeding watchdog.[/quote]

Do you have logs or something that confirms that k_timer_start() actually got called and that it was not something else that failed during startup? Please also try to test your minimal application with SDK v3.2.4 (latest stable release at time of writing)

RE: NRF54L15 Timer interrupt not generating after few cycles

darav — Fri, 27 Mar 2026 10:24:50 GMT

[quote userid="4240" url="~/f/nordic-q-a/127458/nrf54l15-timer-interrupt-not-generating-after-few-cycles/563924"]

.That is the only timer instance we are using based on which other timing related activities are executed.

I'm not sure how to interpret this. My understanding is was that you were starting several timers, but that only one was failing.

[/quote]

sorry for the unclear response. we are using that single timer instance.
For debugging purposes what we implemented following code -:

/* ticks variable is incremented from the timer instance ISR at frequency of once every milisecond*/
while(1){
    main_application();
    if(ticks>1){
        printf("some debug print");
        task_wdt_feed(task_wdt_id);
    }
}

Due to this implementation logically, if the timer is working properly ticks variable will be greater than 1 and the if condition will be true which will keep on feeding watchdog.
When the timer instance fails, the if condition is not satisfied for period greater than watchdog timeout and the device should reboot from watchdog elapsed callback.

But now what we've observed is when the issue for timer instance is reproduced, the if condition is not satisfied and yet the watchdog timer callback is not called and device is not rebooted. so i'm guessing that when the timer instance is failing, watchdog is also failing.

One more observation - If we keep the device wakeup intervals to be short (every ~2 mins) the issue does not seem to be reproduced. But occurs almost everytime when the wakeup interval is >30 mins, after 18 hours or sometimes more.

RE: NRF54L15 Timer interrupt not generating after few cycles

Vidar Berg — Tue, 24 Mar 2026 07:59:45 GMT

Yes, but the timer instance is also running off the GRTC.

[quote user=""]so the device wakes up, but one of the main timers our application uses does not generate interrupts[/quote][quote user="darav"].That is the only timer instance we are using based on which other timing related activities are executed.[/quote]

I'm not sure how to interpret this. My understanding is was that you were starting several timers, but that only one was failing.

RE: NRF54L15 Timer interrupt not generating after few cycles

darav — Tue, 24 Mar 2026 05:24:51 GMT

[quote userid="4240" url="~/f/nordic-q-a/127458/nrf54l15-timer-interrupt-not-generating-after-few-cycles/563735"]so if there were an issue with the GRTC triggering, I would expect all timer instances to fail, not just one. Is it always the same timer that fails to run? [/quote]

I dont think there is an issue with GRTC triggering, as the device does wake up at stipulated interval via GRTC interrupt from system off mode, after which the timer instance fails.That is the only timer instance we are using based on which other timing related activities are executed.

Sure, we will reduce the sleep intervals and check if we can reproduce it more frequently and taper down the scenario variables. Do you have any suggestions for some debug prints that we might need to debug this better?

RE: NRF54L15 Timer interrupt not generating after few cycles

Vidar Berg — Fri, 20 Mar 2026 07:12:11 GMT

Thanks for confirming. We will need to troubleshoot this further to understand why the timer instance is failing to run, as there is currently not much information to go on. All Zephyr timer instances and the scheduler run off the GRTC, so if there were an issue with the GRTC triggering, I would expect all timer instances to fail, not just one. Is it always the same timer that fails to run?

I suggest modifying the project to use shorter sleep intervals (or other adjustments) to see if you can reproduce the issue more frequently, which should make debugging easier.

RE: NRF54L15 Timer interrupt not generating after few cycles

darav — Fri, 20 Mar 2026 05:42:46 GMT

Yes, we are using z_nrf_grtc_wakeup_prepare() function as in the system OFF sample, immediately before entering system OFF.
We are using SDK version 3.0.2

[quote userid="4240" url="~/f/nordic-q-a/127458/nrf54l15-timer-interrupt-not-generating-after-few-cycles/563436"]

This applies to the TIMER peripheral, but the zephyr timer is using GRTC.

[/quote]

Oh. Then what can be the reason for the behaviour we are observing ?

RE: NRF54L15 Timer interrupt not generating after few cycles

Vidar Berg — Tue, 17 Mar 2026 12:17:37 GMT

Hello,

Are you using the z_nrf_grtc_wakeup_prepare() function as in the system OFF sample here: https://github.com/nrfconnect/sdk-zephyr/blob/main/samples/boards/nordic/system_off/src/main.c before entering System OFF? Also, which SDK version are you on?

[quote user=""]

While investigating, we found that this behavior appears related to the following erratum:

nRF54L15 Rev2 anomaly L15_25
https://docs.nordicsemi.com/bundle/errata_nRF54L15_Rev2/page/ERR/nRF54L15/Rev2/latest/anomaly_L15_25.html

[/quote]

This applies to the TIMER peripheral, but the zephyr timer is using GRTC.

Best regards,

Vidar