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Using RTC with LoRa

Associate III

Hello guys!

I'm working with STM32WL series using the LoRa application, for that the RTC must be in binary mode.

However, I need the calendar and timestamp for my project, which implies that I need to use BCD mode.

I'm aware that the RTC3 has the mixed mode, however, whenever I tried using it, the whole project stopped working.

I've been reading the AN4759, and the posts about it in the community, but I have some doubts about the solution.

LoRa uses the alarm A, which requires the subseconds alarm, and I know that the calendar doesn't work in binary mode, but can I activate somehow by software the calendar and timestamp still in binary mode? (if so, how and where in the code?)

Other thing, while using the mixed mode, what I have to do to make it work like in binary mode but with the calendar? Like, I saw that I might have to transform binary date to BCD, is it necessary? If so, I'm confused how and where in the code I do this. Also I need to adjust the alarm A again, right? What do I have to correct in this case?

Thanks in advance!

ST Employee

Hello @FPicc.1 

RTC is indeed reserved for SUBGHz, if you want to get a calendar you can use the time system Offred by the stm32_systime (available in utilities) which provides the time feature based on RTC, please have a look. With it you can dynamically set the time, get the time and maintain it to configure a calendar (main APIs and how to use described in AN5406).

Best Regards.


To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

Thanks for the reply @STTwo-32 , but would I be able to update the timestamp value of the SysTimeMkTime() function, for example, every second?
Can I get a continuous timestamp from these functions?

Associate III

I am stuck with the same situation and the closest I got was to realize that the STM32duino Lorawan wrapper (apparently also provided by ST) seems to use RTC in mixed mode by default and uses Alarm B for the Lorawan stack timing.

There is an example with a calendar alarm and Lorawan, so it seems to work.

Let me know if you got it to work!