Using RTC to get real time for nRF9160DK

[Adeel]

Hi Dev team,

I had an issue regarding getting the real time using RTC. I tried to follow the below dev zone blog but the CAL_RTC does not work in my code.

As such, I am unable to use this to build my application. Does nR9160DK not support "CAL_RTC" like "NRF_CLOCK" .

Can you let me know how I could use the below code to build my app for nRF9160DK.

https://devzone.nordicsemi.com/f/nordic-q-a/51781/rtc-31st-date-problem-in-nrf52840

Also, a question regarding RTC and LFCLK. How can I view the real time value using RTC and LFCLK.

I can see in the debugger that they are running but I need to know the real time through it. Some help in explaining this would be appreciated :).

Regards,

Adeel.

[ovrebekk]

Hi Adeel

How does this case relate to the other one you opened recently?
https://devzone.nordicsemi.com/f/nordic-q-a/64931/using-rtc-to-control-the-real-timestamp

For simplicity I will handle both. 

CAL_RTC is simply a define in nrf_calendar.h, and is defined to NRF_RTC0 by default. 

Please be aware that this example is not developed for NCS/Zephyr, so I am not sure how well it works there. Ideally it would have to be modified to use the nrfx drivers, which are supported both in the nRF5 SDK and in NCS. 

Best regards
Torbjørn

[Adeel]

Hi Tobjorn,

I am basically stuck in an issue wherein I need to get the real time and schedule certain events at that time.

The idea here was to use LFCLK and RTC to try and obtain the real time and schedule events and interrupts based on that.

For that, I needed an idea in order to get and schedules events and interrupts through RTC and LFCLK.

Regards,

Adeel.

[Adeel]

Hi Tobjorn,

Yes, I had tried this basic RTC example and it worked for me. I was working on the other example as it was more of what I wanted when working with an interrupt.

https://github.com/andenore/NordicSnippets/blob/master/examples/rtc/main.c

The code works and I was trying to generate an interrupt on a compare event and that does not happen.

I want to generate a compare event every 10 secs and so I set my CC[0] value to 327680. I want to trigger an interrupt as soon as the compare event is achieved and the interrupt should join back to the original program after 10 secs.

When I run the code and view it in debug mode, I see that the counter as well as the compare register CC[0] resets to zero after the compare is achieved and the interrupt is not triggered. I assume that the code has to execute the interrupt handler RTC0_IRQHandler() after the compare event is done and the CC[0] value should not be reset to 0 automatically after the compare event.

I have used the same code above and just changed the CC[0] value to 327680.

Can you help me in identifying the issue here. 

Regards,

Adeel.

[ovrebekk]

Hi Adeel

Would the k_timer approach I suggested in one of the other cases be an alternative?

It shouldn't be necessary to use a dedicated RTC for timing, since you have Zephyr timers available (similar to the app_timer module in the nRF5 SDK, if you have any experience with that). 

Best regards
Torbjørn

[Adeel]

Hi Tobjorn,

Yes. It could be and I am able to use the k_timers for generating timer interrupts after a certain defined time interval. But I also wanted to generate interrupts through an interrupt handler function that caters to the interrupts instantly through a handler.

I tried it in the example mentioned above to try and enable an interrupt through NVIC_EnableIRQ (RTC0_IRQn). As per my understanding , this enabling of the interrupt should transfer the program to its handler function : void RTC0_IRQHandler(void) wherein I have a certain task written inside the handler function.

Is there another example with the interrupt handler functions wherein I could check its functionality. I am basically trying to work on high priority interrupts.   

Regards,

Adeel.

[ovrebekk]

Hi Adeel

The NVIC API is not supported in Zephyr. 

To enable an interrupt you have to do the following (using the RTC1 interrupt as an example):

IRQ_DIRECT_CONNECT(RTC1_IRQn, 0, RTC1_IRQHandler, 0);
irq_enable(RTC1_IRQn);

Best regards
Torbjørn

[Adeel]

Hi Tobjorn,

Oh okay. I found some examples that used NVIC. Is it compatible for the nRF52 series ?

Regards,

Adeel.

[ovrebekk]

Hi Adeel

It is not supported in Zephyr, no. 

I am guessing all the examples you found using NVIC are based on the nRF5 SDK, not on Zephyr.

For nRF52 development the nRF5 SDK is a good option, and you can use that if you want, but for the nRF53 series, nRF91 series and future chip series we will not support the nRF5 SDK. 

Best regards
Torbjørn

[Adeel]

Hi Tobjorn,

Thanks for the help. This clears up the doubts I had regarding the interrupts :).

Regards,

Adeel.

[ovrebekk]

Great Adeel, I am happy to help

[Adeel]

Hi Tobjorn,

One basic question regarding the same observation:

NRF_RTC0->EVENTS_COMPARE[0] = 0;

NRF_RTC0->CC[0] = NRF_RTC0->COUNTER + 1000;

 Do these commands also not work with the nRF91 series ? I am trying to use them but I see no effect. 

[Adeel]

Hi Tobjorn,

Continuing my previous question, I had an issue regarding setting the RTC compare value for periodic compare events. 

https://github.com/Rallare/fw-nrfconnect-nrf/tree/nrf9160_samples/samples/nrf9160/nrfx/rtc

I used the following example and was building on it. Its working fine for 1 compare event but I wish to have periodic compare events at my scheduled times.

To do that, I am trying to update the compare value by adding it to the counter value in the rtc_handler() part of the code as soon as I get my 1st compare event.

The ideas was this: NEW_COMPARE_VALUE = CURRENT_COUNTER_VALUE + PREVIOUS_COMPARE_VALUE;

For some reason, the compare value does not update and I don't get the next compare event. Could you help me with the code structure that updates the compare value of the counter for periodic events.

Regards,

Adeel.