[ntp:questions] NTP with GPS and RTC

Biebaut Sven sven.biebaut at be.thalesgroup.com
Thu Apr 25 14:51:38 UTC 2013


Hello,

I found confirmation that the kernel updates the RTC every 11 minutes when synchronised with an external source. This leaves me with using my RTC as a reference clock in ntpd.

I found references on the web that is can be achieved with reference driver 43. When I configure ntpd like this, it returns with something like "no reference ids found" .
In the log file /var/log/ntp I can find : refclock_newpeer: clock type 43 invalid

I think this means that there are no valid devices found for the driver to use ?

My RTC is a DS3231 I2C based RTC, with a custom driver. Do I need a special clock driver for this or can I parametrize one of the other reference clock drivers ? Or does my custom driver need extra calls to allow ntp to read its values ?

I cannot find the interface used by ntpd reference clock drivers towards the device clock drivers on the other hand  ( which calls, device node, ..)

Any help is greatly appreciated,

Thanks,



Sven Biebaut
Senior Software Engineer

THALES BELGIUM, S.A.
Rue Freres Taeymans 28
B-1480 Tubize


_____________________________________________
From: BIEBAUT Sven
Sent: 22 April, 2013 10:01
To: 'questions at lists.ntp.org'
Subject: NTP with GPS and RTC


Hello,

on an (x86-based) embedded linux system I would like to synchronize with ntp to a GPS.
When the GPS is present, the local time is updated.
However I would also like that when thus synchronized, that my RTC is also updated, and vice versa, when unsynchronized, that my local time is kept in line with my RTC (that was chosen for precision).

I searched the web far and wide and found staments that both the kernel (every 11 minutes) and ntp ( every 60 minutes) would update the RTC. Unfortunately, I never found documentation or manuals that actually confirm this and how to activate/deactivate one or the other, neither if these staments apply on all or on some versions of ntp or the linux kernel.

My configuration is ntp 4.2.6p2 and my linux kernel is 2.6.34 .

Any help on how this is achieveable is greatly appreciated.

Thanks,

Sven



Sven Biebaut
Senior Software Engineer

THALES BELGIUM, S.A.
Rue Freres Taeymans 28
B-1480 Tubize




Sven Biebaut
Senior Software Engineer

THALES BELGIUM, S.A.
Rue Freres Taeymans 28
B-1480 Tubize





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