I am trying to lock a Windows XP computer to GPS time taking advantage of
both the NEMA sentence and the 1PPS with the hope of getting to within a few
ms.
I am using a Garmin GPS 18PC and the NMEATime program. When I tick the box
to implement the 1PPS feature on NMEATime the program locks up each time it
attempts to correct the PC time. Perhaps there is something I need to do to
configure the GPS 18PC to fix this.
I would be grateful for advice as to whether and how one can use NMEATime
for this purpose with a Garmin GPS 18 PC or advice on other programs to
achieve accurate locking of the PC.
Rex VK7MO
======================================
Rex,
Does the GPS 18PC even have a PPS output? A module which does is this one:
http://www.adafruit.com/products/746
and there are lots of others.
With Windows-8 and a bit of luck, you don't even need the PPS to get within
a millisecond - see:
http://www.satsignal.eu/mrtg/bergen_ntp_2.html
and that's over a Wi-Fi connection! More typically, though, using PPS will
get you within a millisecond = how much depends on the version of Windows
you are using:
http://www.satsignal.eu/mrtg/performance_ntp.php#windows-stratum-1
(PC Feenix is currently playing up, hence the glitches) PC Alta is
Windows-7, and PC Stamsund Windows-8. I also have an XP PC whose graphs are
not so regularly updated:
http://www.satsignal.eu/mrtg/Old-Feenix/feenix_ntp_2.html
using a ublox NEO 6M module from China.
Rather than NMEATime, which uses just a small subset of the capabilities on
NTP, use the standard NTP software from Meinberg, installed as per my
instructions here:
http://www.satsignal.eu/ntp/setup.html
Once that is done, and you have the serial GPS recognised (its performance
won't be that good), add the PPS support with the special driver, as
documented here:
http://www.satsignal.eu/ntp/NTP-on-Windows-Vista.html
Performance of a Windows-7 system using that kernel-mode driver is here:
http://www.satsignal.eu/mrtg/alta_ntp_2.html
Averaged jitter of under 35 microseconds. The Windows-8 system (where the
more precise timestamp instructions are available in the OS) has jitter
under 20 microseconds.
73,
David GM8ARV
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
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