STM32H7 RTC BKUP registers issue

[JosepM Ribera]

Hi

We are using the STM32H7A3ZIT6 for one of our irrigation controllers that we are developing. To check the "power cuts" time, we always save the RTC value (uint_32 seconds value) before voltage goes down, using:

HAL_PWR_EnableBkUpAccess();

HAL_RTCEx_BKUPWrite(&hrtc, RTC_BKP_DR2, Value);

It has been working fine. But, suddenly, in two protos it started to fail. When we read the RTC register using:

HAL_RTCEx_BKUPRead(&hrtc, RTC_BKP_DR2);

We always read 0. Same hardware and same code.

Do you have any idea of what could be the problem?

Thank you in advance

[Peter BENSCH]

Are you absolutely sure that you have not accidentally triggered the tamper function and thus deleted the RTC backup data registers?

Regards

/Peter

[JosepM Ribera]

Hi Peter

Yes, we have checked it. We don't use any tamper function.

[Pavel A.]

Maybe somebody somewhere activated tamper function and the trigger pin is/was in active state?

Try a fresh new chip.

[JosepM Ribera]

If I remove VBAT (CR2032) for a while (reset RTC), then it works fine. Maybe some register has been activated?? What could be?