Hi Charlie,
Thanks for the suggestions.
Yes, I ran gpsd at a high debug levels (5, 6, 19), and have never seen
any indication of pps activity in the resulting log file. The string
pps does not appear (e.g. grep -i pps gpsd.log). That seems a little
odd; not even in a start up message.
If I hadn't built it myself, I would question whether pps was enabled
during the build.
I was browsing the source code as well, and came to similar
conclusions about TIOCMIWAIT. I am going to add a few debug calls in
the area your mention and see what is happening.
Not familiar with setserial, other than to know it exists. Will check
it out.
Don't think I need the pps kernel patch. gpsd documentation is pretty
clear it is solely a user land program.
I also thought about CTS, sort of as a last resort, just in case there
is something odd about DCD on COM1 on the 7260 (seems unlikely as the
docs say there is full handshaking on COM1). Would need to rewire the
plug to reroute the pps signal to CTS, rebuild with the 'PPS on CTS'
flag and off you go. Well, as I said, if all else fails.
Thanks again for the tips and taking the time to write. I'll let you
know what I find.
Regards
jw
--- In "charliem_1216" <> wrote:
>
> Hi JW --
>
> --- In "jywmpg" <jywmpg@> wrote:
> >
> > Has anyone got GPSD running using the PPS (Pulse Per Second)
> signal to
> > synchronize NTP?
> >
> > I have a Garmin 18LVC connected to COM1 on a 7260, with the PPS
> line
> > connected to the DCD pin of COM1. Using a scope, I can tell that
> the
> > Garmin is supplying a 100 ms pulse to DCD once a second.
> >
> > GPSD is supposed to detect the transitions on DCD and use that
> > information to provide a clock to NTP, via shared memory.
> >
> > Unfortunately, running GPSD at a high debug level shows no
> indication
> > that GPSD sees the PPS transitions on DCD. If the transitions are
> > detected, debug messages should be generated
> >
> > I have removed /dev/ttyAM0 from /etc/inittab, and redirected the
> > console output to COM2 via JP4 and JP2.
> >
> > I have downloaded the GPSD 2.34 and built from scratch, making
> sure
> > that both SHM and PPS are enabled, and that PPS is input on DCD.
> >
> > GPSD is capable of producing both a low resolution clock (derived
> fro
> > m characters arriving on the serial line) and a high resolution
> clock
> > (derived from the PPS signal). The low precision clock works, but
> the
> > high precision one does not.
> >
> > This is demonstrated in the following:
> >
> > # ntpq -p
>
> Before bringing ntpd into the picture, I'd verify that gpsd is
> getting the pps OK. I think there is a level 5 or 6 debug log for
> gpsd that will tell you more details about gpsd finding (or not .. )
> the pps signal.
>
> > remote refid st t when poll reach delay
> offset
> > jitter
> >
>
==============================================================================
> > *SHM(0) .GPSa. 0 l 7 16 377
> 0.000 -198.66
> > 37.583
> > SHM(1) .PPSa. 0 l - 16 0 0.000
> 0.000
> > 0.061
> > tss1 .STEP. 16 u - 64 0 0.000
> 0.000
> > 0.000
> > tss6 .STEP. 16 u - 64 0 0.000
> 0.000
> > 0.000
> > LOCAL(0) .LOCL. 10 l 8 64 377 0.000
> 0.000
> > 0.061
> >
> >
> > Questions:
> >
> > 1. Does anyone have this setup working?
>
> No (haven't tried), but I'd like to someday ....
>
> > 2. Is there some other way to monitor the DCD line to see if it is
> > actually getting into the 7260?
>
> Try the oldie-but-goody statserial to monitor it; there is a debian
> package for it.
>
> >
> > Any suggestions would be appreciated.
>
> A few things to try:
>
> * There is a patch for "setserial" program that adds a 'hardpps'
> command option and does the needed ioctl on the port. See:
> http://wiki.enneenne.com/index.php/LinuxPPS_support#setserial
>
> * Reading through the gpsd sources, I see that it needs or at least
> wants TIOCMIWAIT to be defined, so it can 'wait for a change on
> serial input lines'. Can you check to be sure this define is
> picked up when compiling gpsd? Maybe it is missed in a
> cross-compile; gpsd skips pps entirely if TIOCMIWAIT is not
> available.
>
> * There was a pps patch for linux 2.4 kerenls maintained for a long
> time. Google for 'ppskit' (assuming here you use a 2.4 kernel; if
> not, see the 2.6 pps stuff at
> http://wiki.enneenne.com/index.php/LinuxPPS_support).
>
> * There's a gpsd build option to use CTS instead of DCD, maybe give
> that a shot. Unlikely though.
>
> HTH, ......... Charlie
>
> >
> >
> > jw
> >
>
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