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

Long, Darren Darren.Long at uk.thalesgroup.com
Tue Sep 27 13:41:04 UTC 2011

> -----Original Message-----
> Darren,
> I can't help with the second query, and only make suggestions for the 
> first query.  I have run serial NMEA devices on XP, with 
> various versions 
> on NTP.  I've tested both real serial ports, and one Sitecom 
> serial-over-USB connection.  As far as I know all have 
> behaved correctly, 
> but I have been using the PPS and not just the serial NMEA 
> data, and this 
> is obviously different to your tests.
> I would suggest looking with a different program from NTP to 
> see how well 
> the serial data is received.  Does it work?  Perhaps try Visual GPS:
>   http://www.visualgps.net/VisualGPS/default.htm

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.

> You should also be aware that without PPS, using just serial 
> NMEA data is 
> likely to provide not better a performance than just syncing 
> to Internet 
> sources.

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 GPS
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.

> The default baud rate for GPS devices is 4800, but I presume you have 
> allowed for that in your config, as you have success on Linux.

Yep, I've tried running the GPS emulator at 4800 baud with RMC only at 1Hz
and even then, nmea_receive() is never invoked on Win XP.

> So just some ideas which may help.

David, your consideration of my problems is appreciated.  Which version of
the NTP RI are you using?  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've installed NTP with the Meinberg installer and
have been running an alternative ntpd built from source using VS2008.



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