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List:       gpsd-users
Subject:    [Gpsd-users] Problem with PPS on FreeBSD
From:       Rich Wales <richw () richw ! org>
Date:       2009-10-22 6:40:10
Message-ID: 4ADFFE4A.2000606 () liberation ! richw ! org
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I've started experimenting with gpsd (2.39) on a FreeBSD 7.2-RELEASE
system, using a custom kernel (built with the PPS_SYNC option) and a
Garmin GPS 18x LVC (with the PPS signal wired to the carrier pin).

Gpsd can read the NMEA sentences from the GPS just fine, but I'm not
seeing the PPS data at all.  I've tried running gpsd with "-D6", but
there is no mention of any PPS events in the syslog output.  And I'm
also using ntpd (interfacing to gpsd via shared memory), and ntpd
sees the NMEA-based time fine, but it's not seeing any PPS timestamps.

I also tried this same setup on Linux 2.6 (Ubuntu Karmic beta), and
gpsd was able to see the PPS data just fine under Linux, so I'm
confident that I have the GPS properly wired and configured to send
the PPS signal.  But I want to handle PPS in the kernel (for better
accuracy and stability), and I'm feeling more comfortable building a
custom FreeBSD kernel than a custom Linux kernel, so I want to get
this working in FreeBSD if at all possible.

My ultimate goal is to build an NTP time source.  I tried having
ntpd talk directly to the GPS (including PPS) via its own builtin
driver, but I was having stability problems (possibly due to the
same issue that is preventing gpsd from seeing the PPS signal?),
so I decided to try gpsd and see if it would interface any better
with the GPS.

Suggestions, anyone?

Rich Wales
Palo Alto, California, USA
richw@richw.org
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