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

jack j.jack.wang at gmail.com
Fri Nov 27 16:09:06 UTC 2009

Hi all,

After reading Dave Hart's message, I realized that I didn't configure
the GPS device to only emit $GPRMC messages. After doing this, the NTP
software starts to function. So that's big progress for me.

Right now, I am using:

server minpoll 4 prefer
server minpoll 4

NTPStatus shows that it's syncing to PPS(1) although the offset and
jitter are still quite big (-3ms and 0.2ms respectively).

I tried the following combination but the offset actually increased.
server minpoll 4 prefer
fudge flag1 1

Right now I am trying to figure out how to switch to kernel mode. I
1) serialpps.sys
2) the correspond DLL
3) the environment variable that points to the DLL
I am unclear as to what should be done to switch to kernel mode.

Thanks to all for the help.


On Nov 27, 9:12 am, jack <j.jack.w... at gmail.com> wrote:
> David,
> You assumed right. I did start with a USB emulated port. The GPS I
> bought is from U-Blox and it has both USB and serial output. The
> serial output has the 1PPS signal (with an LED indicator). I thought I
> would start with the USB output since it's rather hard to find a
> computer with a serial port. Also I would like to see the accuracy by
> using the USB port only. I later switched to a machine with a serial
> port and started using the serial output of the U-Blox GPS device and
> 1PPS. My objective is to use two of these devices to sync two separate
> computers to within ms so they can share time-sensitive data (time
> stamped).
> I left the device running overnight and I noticed it computed an
> offset at one time. It's currently not updating (everything is zero
> now). I will read carefully what Dave Hart said and follow his advice.
> Thanks to everyone for your help.
> Jack
> On Nov 27, 1:51 am, "David J Taylor" <david-tay... at blueyonder.not-this-
> bit.nor-this-part.co.uk.invalid> wrote:
> > "jack" <> wrote in message
> >news:9db25657-9837-4ebe-ab32-ce15ae968af8 at j35g2000vbl.googlegroups.com..

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