[ntp:questions] Problems with NMEA refclocks, Ublox6 GPS, on WinXP with 4.2.7p21 4

David J Taylor david-taylor at blueyonder.co.uk.invalid
Wed Sep 28 05:10:26 UTC 2011

> Yep, I have no issues reading NMEA data from any of the sources I've 
> tried
> using other code we're developing and also with terminal emulators like
> putty and hyperterm.

OK, Darren, but I would still like to know whether Visual GPS works, just 
for interest.

> I understand this to be the case, but we're operating in an island of
> connectivity and have no real alternative to adopting this approach, 
> other
> than to not hook up the GPS to ntpd and simply set the system clock to 
> time in the background, and use the local clock as the only reference. 
> Its
> my arguably uneducated (I've just bought the Mills book, so this may 
> change)
> guess that the alternative approach would be worse.

Yes, if you can get GPS to work, that would be better.  Any chance you 
could try a GPS device which is known to work such as the GPS 18(x) LVC or 
Sure electronics evaluation board?


> David, your consideration of my problems is appreciated.  Which version 
> of
> the NTP RI are you using?

I don't understand RI.

> Have you needed to resort to use of any of the
> alternative serial.sys files that my googling has found mention of, or
> anything else like that?

I have used Dave Hart's serialpps.sys as it provides kernel-mode 
timestamping, but it's a refinement rather than a necessity.  Tests I did 
showed a average jitter reduction from 5 microseconds to 2 microseconds on 
a lightly loaded Windows system.

> I've installed NTP with the Meinberg installer and
> have been running an alternative ntpd built from source using VS2008.
> Cheers,
> Darren

I use the NTP downloads from:


and the actual versions in use are listed at the bottom of this page:


BTW: I'm not seeing Dave Hart's messages on the NNTP server.

Typically, I install the Meinberg version, and then overwrite the binaries 
with Dave Hart's version.  I have once compiled my own with VS 2010 
Express, but I am not comfortable working in C/C++.  Delphi is my 
preferred language, and one I find highly productive.


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