[gpsd-dev] gpsmon vs PPS via USB

[Hal Murray]

I have more info on the problem I was chasing.

If I run gpsmon direct, it appears as if the PPS stuff isn't working.  If I 
wait long enough, eventually the PPS Offset gets filled in.  If I keep an eye 
on it, it doesn't change very often.

Sometimes, "long enough" is several minutes.  It phases in and out, or 
something like that.  Right now, I haven't seen one in several minutes, but a 
while ago I could get one within well under a minute.

I've got a scope on the PPS pulse.  It's 100 ms.  This is through a FT232.  
The GPS device is a Garmin 18x LVC.  The RMC and GGA blocks are updated only 
on even seconds.  I don't know how this was setup.

I can get log files if that will help.

Does anybody have a really low level debugging hack that tests/logs info from 
TIOCMIWAIT?

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The gpsmon logging stuff should include time stamps.

There should be some way for gpsmon to display the time offset that it would 
send to NTP via SHM.  I don't see any obvious empty space on the screen.  If 
nothing else, it could use the PPS space or alternate with the PPS info, 
perhaps via a keyboard command.

Or perhaps a higher level keyboard command to switch into timekeeping 
debugging mode rather than position debugging mode.


-- 
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