How to use backup registers without setting up RTC ?

[migmel]

Hello,

I have a question: I want to use the backup registers to recover data after waking up from standby. Is it possible using it without setting up RTC or are they bound to RTC ?

If they are related and setting up RTC is mandatory prior to use the registers, but my circuit does not have a 32768 Hz Krystal. Is it still possible to set up RTC without hardware fault?

Thank you

[waclawek.jan]

Which STM32?

To use backup registers you probably don't need to supply clock to RTC, but maybe this is dependent on the particular model. Surely you don't need to set up and run RTC as such.

This is a relatively simple issue and you should be able to experiment using just the debugger, you don't need to write any program, so try that.

JW

[KnarfB]

The RTC can probably (which STM32?) run on the internal LSI oscillator. This will not be as precise as LSE external for a wall-clock, but is okay for just providing a clock to RTC.

hth

KnarfB

[KDJEM.1]

Hello @migmel​ ,

Could you please precise the STM32 product you are using?

A similar question is already asked here.

I hope this help you.

Kaouthar

[migmel]

Hello guys, thank you for the reply.

I am currently using an STM32L071CB.

In general I am more interested in the backup registers than in RTC itself. RTC is only in case I cannot use the registers without setting it up, but for the sake of knowledge, can I get 32768 Hz from internal LSI ?

[migmel]

This link you shared was useful

Thank you

[KnarfB]

you can route LSI clock to a RCC_MCO pin.