I am using an STM32L4 family MCU. In an application, the RTC peripheral is utilized and clocked from an external crystal:
The problem I have noticed just now is that with time, the RTC timer looses sync. It is not easy to notice in short periods of time, but after leaving the application to log time for entire weekend, I noticed that the RTC timer is over 20 minutes later after my PC timer (they were both synced before the weekend).
What could be the cause of this problem? Its hard to believe for me that the RTC timer is simply this low precision, as I am using an external crystal. I would appreciate all help.