[gpsd-users] PPS Problem with U-blox NEO-7 GPS Under Debian 7.5 (Wheezy)

Hi,

I try to synchronize time of different computers in a Car2X scenario.

I configured gpsd and nptd successfully using the official HOWTO (http://www.catb.org/gpsd/gpsd-time-service-howto.html):

address@hidden:~# ntpq -p

remote refid st t when poll reach delay offset jitter

==============================================================================

…

*SHM(0) .GPS. 0 l 39 64 377 0.000 -24.724 19.001

SHM(1) .PPS. 0 l - 64 0 0.000 0.000 0.000

I also configured ntpd to use the PPS signal, but gpsd doesn’t process the PPS signal provided by the u-blox NEO-7 GPS (see above: “reach” is 0).

I’m not sure if it is a hardware or software problem. I use a slightly modified Intel Atom board. From the manual: “[…] to get exact time informations a CPLD from Lattice is connect to the timepuls pin of the NEO-7. The CPLD is connected to the computer board using the LPC bus.”

Linux recognizes a PPS device (dmesg | tail):

…

[ 36.215407] pps_core: LinuxPPS API ver. 1 registered

[ 36.217828] pps_ldisc: PPS line discipline registered

[ 36.218396] pps pps0: new PPS source acm0

[ 36.218417] pps pps0: source "/dev/ttyACM0" added

But using the PPS signal fails:

address@hidden:~# ppstest /dev/pps0

trying PPS source "/dev/pps0"

found PPS source "/dev/pps0"

ok, found 1 source(s), now start fetching data...

time_pps_fetch() error -1 (Connection timed out)

…

Running gpsd in foreground reports an error (gpsd –n –N –D 4 /dev/ttyACM0):

…

gpsd:INFO: KPPS checking /sys/devices/virtual/pps/pps0/path, /dev/ttyACM0

gpsd:INFO: KPPS caps 1133

gpsd:WARN: KPPS kernel PPS will be used

gpsd:ERROR: PPS ioctl(TIOCMIWAIT) failed: 22 Invalid argument

gpsd:PROG: PPS gpsd_ppsmonitor exited???

Maybe someone has a clue how to narrow down the problem

Thank you,

Benedikt

From:	Benedikt Kleinmeier
Subject:	[gpsd-users] PPS Problem with U-blox NEO-7 GPS Under Debian 7.5 (Wheezy)
Date:	Wed, 21 May 2014 09:59:04 +0200