How to make the Intermittent application with GRTC and LFXO while asleep.

[shibuta]

Hi.

I have been investigating how to use GRTC and LFXO for LFCLK with nRF54L15DK.
In my goal, I would like to make the Intermittent application with sleep and GRTC that works with LFXO even if the MCU stay asleep.

I found the library(nrfx_grtc.h), but I couldn't find the sample named 'GRTC' with the library from ncs 3.0.0.

Do you know how to manipulate the API of GRTC, and properly to write the prj.cof ?

Best regards.

[Vidar Berg]

Hello,

The system clock in Zephyr is already running off the GRTC (or the RTC if you're using a nRF52/53/91 series device). So, let's say you have a single threaded application, you can make it wake up periodically using Zephyr primitives such as k_msleep(). It will be in System ON mode  between the wake ups.

int main(void)
{
    while (1) {
        printk("Woke up. Going back to sleep\n);
        k_msleep(1000);  // Sleep for 1000 ms
    }
    
    return 0;
}

https://docs.nordicsemi.com/bundle/ncs-3.1.0-preview1/page/nrf/test_and_optimize/optimizing/power_general.html 

Best regards,

Vidar

[shibuta]

HI.
Thank you for replying, but where did you find GRTC automatically works responding to power state?
Indeed, I see the k_sleep() go sleep, but I couldn't find that automatic clock source change in your URL document.
The document seemes to state some techniques for power saving.

Anyway, I will try obeying your suggested document.
If I confirm the power consumption become lower, I will report them.

Best regards.

[shibuta]

Hi.

Vidar Berg said:

The system clock in Zephyr is already running off the GRTC (or the RTC if you're using a nRF52/53/91 series device).

Indeed, I found the same statement in DevAcademy as you said.
https://academy.nordicsemi.com/courses/nrf-connect-sdk-intermediate/lessons/lesson-1-zephyr-rtos-advanced/topic/boot-up-sequence-execution-context/
>System Timer driver: This is usually a Real-time counter peripheral (RTC1) on Nordic SoCs and SiPs (nRF91, nRF53, nRF52 Series). On the nRF54 Series, it’s the global real-time counter peripheral (GRTC). The System Timer will be used for the timing services of the kernel, such as k_sleep() and the kernel timer API.

And, do you mean k_sleep() enter not 'the MCU SYSTEMOFF' , but 'the thread sleep' , alright ?
I was too poor to tell you well how problem I encountered, sorry.

I would like to reduce power consumption while not only the main thread also MPU asleep.
According to this page below, nRF54L15 could states 0.8uA with SYSTEMOFF waiting GRTC wakeup.
https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/keyfeatures_html5.html#ariaid-title1

Then, I managed to find the page about GRTC below, but I don't know how to solve this.
How does the solution step require on Zephyr?

https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/grtc.html#d921e539

Best regards.

[shibuta]

Additionally, I found the example code using system-off, named as below.
It was found on "ncs/v3.0.0/zephyr/samples/boards/nordic/system_off".

.. zephyr:code-sample:: nrf_system_off
   :name: System Off
   :relevant-api: sys_poweroff subsys_pm_device

I added in prj.conf as below because I would like to use GRTC wakeup when asleep, running nRF54L15dk

CONFIG_GRTC_WAKEUP_ENABLE=y

CONFIG_GPIO_WAKEUP_ENABLE=n

But, it won't wake up.

*** Booting nRF Connect SDK v3.0.0-3bfc46578e42 ***
*** Using Zephyr OS v4.0.99-3e0ce7636fa6 ***

nrf54l15dk system off demo
Reset by debugger.
Retained data not supported
Entering system off; wait 2 seconds to restart

Is any more library or configuration required ?

Best regards.