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.

[Vidar Berg]

This example should not require any additional modifications besides the configuration changes you made. I also confirmed this by building the same sample on my end. Please try loading the attached hex file to see if you get the same result.

8468.merged.hex

nrfutil command to flash the *.hex file from the command line:

nrfutil device program --firmware merged.hex --options reset=RESET_PIN,verify=VERIFY_READ,chip_erase_mode=ERASE_NONE