Why stm32 rtc doesn't allow time before year 2000

[Martdur]

Trying to implement a timestamp from 0 to the end of life of the product I was using the RTC in order to keep counting when powered only with Vbatt.
But I can't set the time to 0, and can not read without calling rtc_set_time.
Is there a way to write to the rtc register the time value in order to not set the time at run time ?
Why can I set the time to 0 ?

[ajarmouni-st]

Hi @Martdur it's a hardware limitation, see https://community.st.com/t5/stm32-mcus-products/stm32-rtc-fixed-to-21st-century/m-p/177837/highlight/true#M37132

[Martdur]

Hi @ajarmouni-st Thanks for the answer !

It's indeed a hardware limitation.
I'm using a workaround by setting the minimal possible time and then substract the date time with this value to get a counter from 0.