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

[Benedikt Kleinmeier]

Hi,

I try to synchronize time of different computers with GPS and PPS.

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
    [   36.215415] 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,
Benedikt