I'm using Nucleo STM32L476RG board and I have issue using specific configuration of RTC peripheral.
Our embedded software requires precise timing for real time application.
RTC is clocked by 32.768 kHz LSE and is configured with PREDIV_A: 0 and PREDIV_S: 32767 to get time resolution of 1/32768 s.
Then subseconds register will down count from PREDIV_S to 0 and Alarm A interrupt is used to get precise timer from milliseconds to minutes.
This configuration is valid according STM32L4 reference manual.
However we observed strange behavior:
- Timestamp retrieved from RTC are sometimes inconsistent: seconds register did not increment while subseconds register reached 0 and rolled over.
- RTC_OUT configured to output 1 Hz is 128 Hz. 1Hz output is observed only when PREDIV_A and PREDIV_S are set to default values (127 and 255).
I used Cube MX and last HAL drivers.
Did anyone already use this configuration and observe consistent results?