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

From: Benedikt Kleinmeier
Subject: [gpsd-users] PPS Problem with U-blox NEO-7 GPS Under Debian 7.5 (Wheezy)
Date: Thu, 22 May 2014 08:35:21 +0200
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I try to synchronize time of different computers with GPS and PPS.

I configured gpsd and nptd successfully using the official HOWTO (

    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
[ 36.215415] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <address@hidden>
    [   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,

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