undefined reference to `__device_dts_ord_98'

[NicolasK.]

I'm trying to use implement the real time clock rtc0. This is what I did:

I enabled CONFIG_RTC=y in the prj.conf.

&rtc0 {
            compatible = "nordic,nrf-rtc";
            reg = < 0x4000b000 0x1000 >;
            cc-num = < 0x3 >;
            interrupts = < 0xb 0x1 >;
            status = "okay";
            clock-frequency = < 0x8000 >;
            prescaler = < 0x1 >;
};

in the overlay file

#include <zephyr/kernel.h>
#include <zephyr/device.h>
#include <zephyr/drivers/rtc.h>

#define RTC_0 DT_NODELABEL(rtc0)
const struct device *timer_dev = DEVICE_DT_GET(RTC_0);
const struct rtc_time time;

int main(void)
{
        rtc_set_time(timer_dev, &time);
        return 0;
}

in the main

After I added rtc_set_time(timer_dev, &time); it fails to link the C executable zephyr/zephyr_pre0.elf with the error: undefined reference to `__device_dts_ord_98'

What did I forget to do or did wrong? I have the feeling I'm missing something like an additional initiation type function but there is very little documentation on how to actually set it up.

[helsing]

Hi Nicolas,

Does it help to if you try 'rtc' instead of 'rtc0' in the overlay file?

[NicolasK.]

That doesn't work (I tried it). rtc0 already exist in the nrf53840.dtsi (not the .dts) aswell as rtc1 and rtc2. Im using the " &rtc0 { " to point to that location and overwrite its parameters. The only important piece in the overlay is the status = "okay" to enable rtc0 because by default its status = "disabled". The timer_dev seems to be set correctly because there is no complie error, but when I add the rtc_set_time function it gives me said error. :(

[helsing]

Hi Nicolas, sorry for the delay. I will get back to you tomorrow.

[helsing]

rtc_set_time is a part of the Real Time Clock drivers in Zephyr while nordic,nrf-rtc is Real Time Counter. These are not the same.

For real time clock one often needs an external module. For real time clock, there is a Zephyr test here: https://github.com/nrfconnect/sdk-zephyr/tree/main/drivers/rtc

[RuthA]

Hi Helsing,

I'm seeing the same behaviour with an nRF52 dev kit.

DEVICE_DT_GET( DT_NODELABEL( XX ) )

works for other node labels and it looks like it expands to the correct "__device_dts_ord_XX" number for the rtc nodes (rtc0, rtc1 and rtc2 on my system) when checked against the "devicetree_generated.h" file. However, the "rtc_set_time" function can't use the device and I see the same "undefined reference" error as Nicolas (with a different number).

This method of setting the device and then using "rtc_set_time" seems to follow the procedure in this zephyr test: https://github.com/zephyrproject-rtos/zephyr/blob/a51bd53cef2b2b6cacb1dc7a366adb45565659f3/tests/drivers/rtc/rtc_api/src/test_time.c

Can you explain why it's not working or let me know which external modules we need for the real time clock?

Best wishes,

Ruth

[NicolasK.]

Hi Ruth,

I think its like Helsing said. We are confusing real time clock and real time counter. Its not good that they have the same abbreviation rtc (in my opinion it should be more like RTIC (increment counter). The real time counter is similar to the ticks of the MCU [like k_uptime_get()]. The real time clock needs a battery and a quartz which is kept running in order to track time even if the main device is turned off. Usually they are a seperate hardware module like the DS3231. My assumption was that since the nrf52840dk has a battery, its likely it has a real time clock, but I guess I'm wrong.

Helsing please correct me if I misunderstood anything.

Kind regards,

Nicolas