Assuming you are looking for better time than you can get from just
network servers, you can add a local time source.
EASY WAY
If you want good time at low cost, and have a generic PC, connect
something like a Garmin 18x LVC to a serial port and install
FreeBSD. Easy to configure and NTPD has reported jitter in the 1 to
4 microsecond range ever since.
Total elapsed time maybe 2 hours including installing FreeBSD and
mounting the GPS on the roof.
The FreeBSD folks do a very good job of supporting ntpd with local
hardware clock sources, and document it well.
HARD WAY
Linux with PPS is still more of a work-in-progress and you should
expect to have to patch kernels etc. You will find dozens of kernel
postings, 1PPS seems to have ended up as a serial line protocol,
AFAIK it is still not in any distribution base kernel. If you are
doing an ARM you will likely have to modify the ARM's serial driver
to do timestamping, by looking at samples in the 8250 driver PPS
code. Certainly quite do-able, but not in 2 hours for most people :)
-Bob
p.s. It was not obvious from the Garmin instructions, but all you
have to do is crimp the serial wires on the 18x LVC to a 9 pin
connector, placing the yellow 1 PPS wire on pin 1, plug into the PC's
serial port and FreeBSD does the rest. Avoid any PC without an
actual serial port. You can pick up +5v from your PC (use a fuse).
On May 14, 2009, at 2:34 PM, Randy Scott wrote:
Is there any consensus for the reasons why Linux performs poorly?
I was thinking about setting up a server as well (possibly using a
little ARM-based single-board computer that runs Linux).
Randy.
--- On Thu, 5/14/09, Robert Darlington <[email protected]> wrote:
From: Robert Darlington <[email protected]>
Subject: Re: [time-nuts] Linux time servers
To: "Discussion of precise time and frequency measurement" <time-
[email protected]>
Date: Thursday, May 14, 2009, 4:23 PM
RedHat in the 90s was terrible.
It's much better now.
Last thing I read about ntp was that it was kind of broken
for high
precision stuff on Linux and people tend to use
FreeBSD. I duplicated the
work of one of the time-nuts by following his site here:
http://www.febo.com/pages/soekris/
Even with all of the details there it still required a
great effort on my
part to get things up and running to where I have them
now. If you decide
to go this route I will be more than happy to send you a
copy of the image
on my CF card so that you'll have a working system out of
the box. I had to
recompile ntp because the current FreeBSD distro didn't
have support for
something (NMEA I think, of all things!).
-Bob
On Thu, May 14, 2009 at 2:09 PM, Dave Ackrill
<[email protected]>wrote:
Anyone got any good Linux time systems for PCs ?
I now have a PC on my home system that has Linux
fedora on it and I'm keen
to learn how to make it a useful new member of my
network.
I did dabble with Redhat Linux once before in the
1990s, and still have the
scars to show for it, so please don't assume that I
know what I'm doing...
Thanks
Dave (G0DJA)
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