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

unruh unruh at wormhole.physics.ubc.ca
Sat Jun 12 02:46:15 UTC 2010

On 2010-06-11, apobrien <apobrienster at gmail.com> wrote:
> 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.

Use shmpps. It uses the shm driver to input the PPS to ntp. It requires
that you have some other source to derive the seconds from (I, PPS can
allow ntp to condition to the exact second, but has no idea which second
it is conditioning to) That serial port is used to input the PPS and the
seconds. How would you input the PPS in your case?
> TIA!
> Andy

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