[ntp:questions] help with setting up NTP on windows with a USB GPS

jack j.jack.wang at gmail.com
Tue Dec 1 16:58:59 UTC 2009


I would like to add that, from my own experiences, the GPS has to be
configured to output $GPRMC sentences only. Otherwise the PPS part of
NTP doesn't work.

I have a related question: given that my system clock is synced to an
external GPS within ms, how do I read time that gives me the same
accuracy? When I tried to read time at 60Hz, I found that the times
returned are not periodic, sometimes even the same.


On Dec 1, 9:28 am, "David J Taylor" <david-tay... at blueyonder.not-this-
bit.nor-this-part.co.uk.invalid> wrote:
> "Dave Baxter" <g8... at nospam.uko2.co.uk> wrote in message
> news:MPG.257f2d55775bad5a989682 at news.demon.co.uk...
> []
> > Hi David...
> > I'll put the BSOD details in another post, beneath David Harts post, to
> > keep the tree branches sane...
> > You did help me out a while back, by pointing me at the exact same
> > distribution of F'BSD as you used, I managed (at the third attempt) to
> > get it to install on a suiable PC (P3/766MHz, 512M Ram) and it in it's
> > original guise seemed happy.  At least, all the things I tried sort of
> > worked as documented.
> Ah, I remember now....
> > It took me two more attempts to get the kernel recompiled with PPS
> > support enabled (needing another full re-install in the process, though
> > I now know where the "backup" kernel file is if I do that again!)
> I was luckier.
> > My single biggest problem, and no disrespect to you or anyone else here,
> > is that (and I've done exactly the same with stuff I work with for other
> > lesser people) is one is "too close" to it all in many ways to get a
> > truly idiot proof (for that's what us newbies need :) ) install working
> > safely.   (If at all in some instances!)
> I agree, and that's why I have a user-group for my own software and
> encourage people to try beta versions.  Having different people explain
> things in different ways can often be helpful when you have a mental block
> about something.  I've tried to simplify things at the top of my Web page:
>  http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html
> by adding a "for the impatient" paragraph - i.e. for those who don't or
> can't RTFM!  I'd welcome any input to try and improve that page for
> "novices".
> > I think I now know what I did wrong with the serialpps.sys in Windows,
> > you'll probably laugh when you read it in my reply to the other Dave
> > (maybe we should all use the name Bruce instead?)
> You can save playing with that for another day, though,
> > The version on the Meinberg windows port of NTPD I've used so far is:-
> > ntpd 4.24p7 at copenhagen-o May 22 2009   If that helps (as shown in the
> > NTP monitor program)
> > I realy would preffer a stable version, rather than any bleading edge
> > versions, as the rest of the system can be left to it's own devices for
> > weeks if needed with no issues.
> I agree, but the "stable" branch doesn't yet include the PPS support, so
> we're stuck with the "development" branch.  Quite honestly, I would treat
> most of the development branch as being of "production" quality.  I had
> one problem when it wouldn't work with Windows 2000 (now resolved, I
> think, I'm using ntpd 4.2.5p231 on PC Bacchus), and one more subtle
> problem where something didn't work as well after a reboot of a Windows-7
> system.  That's also now resolved.
> > I think I need at least single figure mS stability and resolution, not
> > absolute uS accuracy, but better is sort of better I guess, I'll bow to
> > superior knowledge on that though.
> > There are at least two other Faros users (just thought of someone else)
> > so that's 4 that I know of, who would also like a fully self contained
> > system for this purpose (Faros) as they are not well connected to the
> > 'net, with resulting NTP issues as a reuslt.
> > Have to say, my main problem with this, is that there are so many
> > versions of this and that, plus knowledge I'm still learning is needed
> > to make it fly.
> > Best Regards.  Now to answer Dave Harts post.
> > Dave Baxter.
> Keep asking the questions, even if they seem elementary - and I will try
> to both provide answers and record them on my Web site for others.  One
> issue which you haven't addressed (as far as I know) is how the Faros
> program uses an accurate time.  I take it that the author of the program
> gets the time from Windows - he does know that time is typically only
> updated once every ten milliseconds, I guess?  NTP doesn't have an API
> which can tell you the time more accurately than that, which is a pity
> because that would be very handy....
> 73,
> David

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