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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: Wed, 21 May 2014 09:59:04 +0200



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


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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