[ntp:questions] Local Clock Discipline

David Kuechenmeister kplus13 at yahoo.com
Fri Oct 3 18:15:07 UTC 2003

I have a customer requirement to use an IRIG-B time source for time
stamps on collected data. I've got a Brandywine syncclock card in a
Windows, Embedded XP computer. The problem I've got is getting the
time set on a remote computer, that is linked by ethernet to the XP
time host.

The system is successfully synchronized with NTP and network time
servers, but in this case, IRIG-B time is required. My original
attempt was to set the reference to LOCAL on the XP computer and then
update the clock, based on periodic reads of the syncClock card. This
failed when the jitter on the remote clock was too high. I suspect it
was because the periodic hard resets of the system clock on the XP
computer interfered with the normal NTP operation.

Now that I've done some more reading, it looks like there are two
alternatives. The first is to re-write the IRIG-B clock driver to use
ntp_adjtime kernel calls. The other is to write a reference clock
driver for the ntpd program. I don't think embedded XP has the
ntp_adjtime calls compiled in to the kernel, so that leaves the option
of writing a ref clock driver.

Are there any alternatives that I didn't list, i.e. is there another
way to update the system clock from the IRIG-B source?

David Kuechenmeister
david.kuechenmeister A_T viasat D_O_T com

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