Restore RTC Clock after power off

[dds90]

How would it be possible to keep the time even after the power supply was restored?
Now, when power is restored, the microcontroller restarts from the setup() routine (where there is rtc.setTime), it takes the new time and loses the current time.
Is it possible to implement the programmable voltage detector (PVD) to send the microcontroller in low power mode, and wake up when power is restored without going through setup()?

Thank you in advance

[Stateford]

Shouldn't setRTC be a subroutine that can be called on it's on? AFAIK RTC's have an internal battery that keep time.

Maybe this would help?

http://ww1.microchip.com/downloads/en/AppNotes/Atmel-2575-C-Functions-for-Reading-and-Writing-to-Flash-Memory_ApplicationNote_AVR106.pdf

[fpistm]

You talk about after a call of low power shutdown()?

[dds90]

At the moment I have only implemented the RTC and when I remove the power supply and then poweron the discovery board again, the clock starts from the time that I initially set. I suppose this happens because it's like pressing the RESET button, and then I'm going to reinitialize the RTC.

To keep the time even after restoring the power, how should I do?

[fpistm]

Which board? I assume you have a battery connected to VBAT.

[dds90]

I'm trying with a STM32VLDISCOVERY, so STM32F100RBT6.
I've connected the battery.

[fpistm]

It required to save the date/time in backup registers using HAL_RTCEx_BKUPWrite/HAL_RTCEx_BKUPRead.
This is the first releases of STM32RTC and STM32LowPower, goal was to enable low power which required some RTC services and so this could be extend in further version.
Anyway this use case is mandatory: restore Date/time after standby mode. Ido not talk about PVD.

[dds90]

It required to save the date/time in backup registers using HAL_RTCEx_BKUPWrite/HAL_RTCEx_BKUPRead.

I read this too. Would it be appropriate to change the title and remove the PVD?
I've read also that there is some issue with the date backup.

Anyway this use case is mandatory: restore Date/time after standby mode.

Do you think that you could process it in a further version?

Moreover, if you will get this board, like you wrote previously, after connected the battery, is necessary to remove the SB1.

[fpistm]

Yes it will be an enhancement.
And yes by default VBAT is connected to VDD on ST boards

[dds90]

Indicatively, what times for processing and release do you suppose?

[fpistm]

I don't know exactly. Several stuff in //. I will do my best.

[dds90]

Thank you very very much!