[gpsd-users] GPSD, PPS, Garmin 18x LVC and 93 meters of serial cable

[Sander Smeenk]

Hi!

I'm trying to use a Garmin 18x LVC GPS receiver to provide a stratum1
time source in our network. The receiver is connected to the server by
93 meters of CAT6 UTP over which the GPS' serial outputs are
patched/connected.

TX/RX is working fine, i get clear NMEA sentences from the GPS, however
the pulse is failing and that's exactly what's most important. ;)

The GPS does have a 3DFIX et al, so it's not that it doesn't have any
fix to pulse from.

I've tried to measure the pulse and it came up with 4.84 volts, however
the server is not registering the pulse. Also, gpsd 3.11 when starting
up logs "pps":false consistently while on another box with gpsd 3.10 it
always starts with "pps":true and gpsmon sporadically registers (logs) a
PPS pulse.

What makes gpsd 'enable' the PPS 'subsystem'?
Why is one box (3.10) seeing/trying to see it while the other one (3.11) isn't?

I'm now reading about the ground pins not being exactly zero volts, that
might cause the signal not to register correctly for RS232-specs?
Perhaps the one box is more 'sensitive' than the other? I'm just
guessing...

Thanks in advance for any input!

-Sndr.
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