We have a device based on RaspberryPi running recent Raspbian Linux.
We are using TCXO based RTC which should keep time within ±3ppm (PCF2129).
We also expect that some devices will work completely without network all the time so they will never see any NTP server.
I would like to have the most precise time on my device.
What I would like to do is to use RTC time in holdover (RTC->sys) and synchronize RTC in normal operation (sys->RTC).
User will be able to manually set correct time in offline device if needed so this should also propagate to RTC.
I know that rtcsync option will do the sys->RTC
I know that with refclock, I can implement SHM/SOCK driver which do RTC->sys but this will prevent rtcsync on the same RTC.
Is there a possibility to realise this so I can have both RTC->sys and sys->RTC depending on situation?
Jan Breuer