[ntp:questions] proprietary hardware clock as NTP reference source

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Sat Jun 12 01:30:12 UTC 2010

In article <40aa2d27-9826-4948-a405-e5b311358eba at z8g2000yqz.googlegroups.com>,
 apobrien <apobrienster at gmail.com> writes:
>Hello list,
>I have a set of proprietary hardware timing cards (Symmetricom
>bc635PCIe) which synchronize their clocks using a dedicated
>interconnect.  As you might imagine the timing card conditioned time
>drifts from that of the hosts they're installed in.
>What I'd like to do is make the "master" timing card's time into a NTP
>reference clock then use NTP to distribute that time to the other
>hosts in the (private) network.
>I've looked at Orphan mode and undisciplined local clocks but they
>only refer to the host's software clock if I'm not mistaken.  I've
>also searched through the archive but I'm afraid I lack the
>appropriate terminology to get meaningful results.
>Can someone point me toward (some google words maybe) creating an
>arbitrary NTP reference source (under Linux)?  I think I'm just
>missing something very basic.
>I've been looking at the LinuxPPS project as these cards output a PPS
>that I might use to condition the host clock using Linux PPS but I
>don't have a 8250 serial port on these new fangled PCs.

I think you have two choices.

One is to write a stand alone program that talks to your hardware
and puts the info into shared memory where the shared-memory driver
(driver 28) can get it.  gpsd works this way.

The other is to write your own refclock-driver.  The usual
approach is to find a driver that is as close as you can get
and modify it.  If your changes are small and don't break the
old moce, you may be able to convince the ntp project to merge
them into the main source package.

It may be tricky to get started this way.  The best documentation
is to read the code.  There is some overview here, but it
probably won't help much until you look at the code:

These are my opinions, not necessarily my employer's.  I hate spam.

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