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

Dave Hart davehart at gmail.com
Fri Nov 27 04:16:21 UTC 2009

On Nov 26, 9:30 pm, jack wrote:
> I found the following entry in the log file:
> Using user-mode PPS timestamp
> Does it mean NTP reads the GPS strings and sees the 1PPS signal?

Pretty much, yes.  That message occurs only upon reading a CR when a
DCD transition has been observed and its timestamp is used instead of
the end-of-line CR/LF timestamp.  That "user-mode" PPS hack only works
if the GPS is configured to emit only one sentence per second, and it
allow you to get most of the benefit of PPS without requiring

Since the topic mentions a USB GPS, unless the GPS is documented to
deliver PPS via its emulated serial's DCD, you may be seeing
meaningless DCD transitions rather than PPS.

You have serialpps.sys, so you might consider enabling PPSAPI use by
the NMEA refclock driver using

fudge flag1 1

Good luck figuring out the problem that's keeping it unreachable.

Dave Hart

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