[ntp:questions] Re: Bought a GPS receiver--What next?
Richard B. Gilbert
rgilbert88 at comcast.net
Mon Nov 1 22:17:13 UTC 2004
W. D. wrote:
>I bought this Motorola Oncore GT+ unit from
>the affable Mr. John Gibbons:
>It starts blinking its pulse-per-second blue LED just a
>few seconds after the power is turned on, and sounds in
>sync with WWV on 5 mhz.
>I've searched through lots of documentation on how to get
>NTP (on FreeBSD) to use the PPS signal it generates, but I have
>a few questions.
>First of all, this page seems to be the most complete
>page for configuring GPS:
>He says that you need to rebuild the kernel, but others
>say that it's possible to get better accuracy if you don't.
>What's the real, full story?
>Somewhere I read that you need to load the following
>Where does it need to be loaded? Why isn't there a
>reference to it on the Pilikia page? Are there
>any other things I need to know about getting
>this receiver integrated?
>Also, once everything is configured properly is it
>possible to talk to this unit to find out my
>latitude, longitude and elevation? How many satellites
>Thanks kindly for your advice!
Assuming that your version of NTP (you didn't specify) was built with
all the refclock drivers, you should be able to connect your Motorola
Oncore GT+ to a serial port and configure it as directed by the
documentation for that version! I've only configured an Oncore on ntpd
4.2.0 which requires two links, /dev/oncore.pps.0 and
/dev/oncore.serial.0 pointing to your serial port. Next you need
/etc/ntp.oncore0 which is configuration file that looks something like this:
# Reference Clock configuration for Motorola Oncore M12
# Five Choices for MODE
# (0) ONCORE is preinitialized, don't do anything to change it.
# nb, DON'T set 0D mode, DON'T set Delay, position...
# (1) NO RESET, Read Position, delays from data file, lock it in, go
to 0D mode.
# (2) NO RESET, Read Delays from data file, do SITE SURVEY to get
# lock this in, go to 0D mode.
# (3) HARD RESET, Read Position, delays from data file, lock it in,
go to 0D mode.
# (4) HARD RESET, Read Delays from data file, do SITE SURVEY to get
# NB. If a POSITION is specified in the config file with mode=(2,4)
# then this position is set as the INITIAL position of the ONCORE.
# This can reduce the time to first fix.
LAT 39 45.3753 # Positive is North.
LONG -75 04.27187 # Negative is West
HTGPS 18.28 M # Height in meters.
TRAIM YES # May need this if antenna position is suboptimal.
Finally, you need to add a server statement in /etc/ntp.conf:
# Reference Clock (Motorola Oncore M12)
server 127.127.30.0 prefer
All this stuff is, AFAIK, version specific. What I have shown here is
working on a Sun Ultra 10 running Solaris 8. Your mileage may vary.
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