Zephyr RTC build issue.

RE: Zephyr RTC build issue.

Mark P Clark — Mon, 03 Nov 2025 21:51:18 GMT

Greetings,

Thanks for following up! I have had limited success using the RTC APIs. I created 2 rtc_time structs:

// 2:15:10, August 20, 2025, Wed, 232nd day, DST = unknown, nanosecs = 0 (unknown)

struct rtc_time Set_clock_time = {10, 15, 2, 20, 8, 125, 3, 232, -1, 0};

struct rtc_time Get_clock_time = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};

Calling int Set_TM_ret = rtc_set_time(rtc_ptr, &Set_clock_time); returns success (0) and appears to start the RTC. I can see the NRF_RTC_Type* regs->COUNTER value increasing at the 32.768 kHz clock rate.

Calling int Get_TM_ret = rtc_get_time(rtc_ptr, &Get_clock_time); returns success (0) however the Get_Clock_time struct is not changed - any thoughts on why that might be happening?

For our application we would like to set the pre-scaler to 1 mS (value = 32). It seems that I have to stop the RTC to set the pre-scaler -> regs->TASKS_STOP = RTC_TASKS_STOP_TASKS_STOP_Trigger

After that I can see the counter advancing at the 1 mS rate. When I do this it appears to cause issues with the radio. The peripheral is advertising OK and connects briefly and then disconnects. I captured a trace using the Bluetooth Low Energy App and it is showing this repeatedly:

00> [00:06:05.920,959] <wrn> bt_conn: conn 0x20002488 failed to establish. RF noise?

00> [00:06:05.921,447] <inf> HnB_NUS_module: Disconnected: 73:36:87:1F:7A:91 (random), reason 0x3e

Taking out the RTC init the peripheral is able to connect with the central and read device info OK. Any thoughts on how the RTC initialization could be affecting the radio?

I am using rtc0 for my testing and we don't have a 32.768 kHz crystal on our PCB so in prj.conf, I am setting:

CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y in prj.conf to force RC oscillator for LFCLK.

I appreciate your feedback on these issues with the RTC on the NRF52832.

Best Regards,

Mark

RE: Zephyr RTC build issue.

Dhivin John — Thu, 30 Oct 2025 14:11:30 GMT

Hi,

I wanted to clarify — were you actually able to use any Zephyr RTC API functions (like rtc_get_time() or rtc_set_time()) with that rtc_ptr, or did the code just compile successfully only?

Just wanted to confirm if the RTC hardware is functionally working under Zephyr’s RTC API, or if it’s just a build-time symbol resolution fix.

Thanks,

RE: Zephyr RTC build issue.

Mark P Clark — Mon, 25 Aug 2025 20:00:15 GMT

Greetings and thanks for the additional input!

Initially I tried changing the nrf52dk_nrf52832.overlay file which gave me the same build error. Revisiting the l3_e2 tutorial; I used the DeviceTree Visual Editor and under SOC I could see that the rtc0/1/2 were not enabled. after enabling rtc0 it updated app.overlay file at the same level as the /src directory. This added:

&rtc0 {
status = "okay";
};

After that I am able to build successfully and setup the device pointer as follows:

const struct device *rtc_ptr = DEVICE_DT_GET(DT_NODELABEL(rtc0));

I would have expected the overlay file in /boards to have the same effect, evidently the app.overlay file takes precedence.

Thanks much for your help with this issue!

Best regards,

Mark

RE: Zephyr RTC build issue.

deiwo — Sat, 23 Aug 2025 22:37:34 GMT

I suggest adding this to the overlay instead what you have:
&rtc0 {
status = "okay";
}

And I would not comment out the offending line, it should work if the rtc is enabled properly.

I recommend reading the tutorial on how to use the devicetree here: https://academy.nordicsemi.com/courses/nrf-connect-sdk-fundamentals/lessons/lesson-2-reading-buttons-and-controlling-leds/topic/devicetree/

and here is the tutorial for the overlays: https://academy.nordicsemi.com/courses/nrf-connect-sdk-fundamentals/lessons/lesson-3-elements-of-an-nrf-connect-sdk-application/topic/configuration-files/

What you should do is similar to what they did in the tutorial for overlays with spi, but in your case it should be rtc.

RE: Zephyr RTC build issue.

Mark P Clark — Fri, 22 Aug 2025 19:24:33 GMT

Greetings and thanks for the input!

I modified the nrf52dk_nrf52832.overlay file to add this:

/ {

chosen {

nordic,nrf-rtc = &rtc0;

};

In \zephyr\zephyr.dts - RTC is included as follows:

rtc0: rtc@4000b000 {

compatible = "nordic,nrf-rtc";

reg = < 0x4000b000 0x1000 >;

cc-num = < 0x3 >;

interrupts = < 0xb 0x1 >;

status = "disabled";

clock-frequency = < 0x8000 >;

prescaler = < 0x1 >;

};

Building with the line offending line commented: // const struct device *rtc_ptr = DEVICE_DT_GET(DT_NODELABEL(rtc0));

and the .overlay change above results in a similar error:

C:/ncs/v2.9.0/zephyr/include/zephyr/device.h:92:41: error: '__device_dts_ord_DT_CHOSEN_nordic_nus_uart_ORD' undeclared here (not in a function)
92 | #define DEVICE_NAME_GET(dev_id) _CONCAT(__device_, dev_id)

Perhaps, there is a better way to enable RTC in the board definition?

Thanks and Best regards,

Mark

RE: Zephyr RTC build issue.

deiwo — Fri, 22 Aug 2025 09:32:18 GMT

Hi, this usually happens when the RTC module is disabled in the board definition. Do you have it enabled?