[ntp:questions] pps coming in, not received by ntpd

folkert folkert at vanheusden.com
Sat Jun 29 17:57:21 UTC 2013


Hi,

Something odd is happening.
I've connected a garmin 18 lvc to a pc.
The system has a kernel with pps support and i verified it comes in:

root at hoei:/home/folkert# cat /sys/devices/virtual/pps/pps0/{assert,clear}
1372528130.997131540#54
1372528131.097120120#54

I'm running gpsd and it says the gps has a fix and it also has all
appropriate devices open:

gpsd      27762           nobody    7u      CHR               4,65 0t0       1144 /dev/ttyS1
gpsd      27762           nobody    9r      CHR              251,0 0t0      82440 /dev/pps0

gps is started with '-n'

ntpd is configurated to listen to the shared memory segments:

server 127.127.28.0 minpoll 4
fudge  127.127.28.0 refid NMEA
server 127.127.28.1 minpoll 4 prefer
fudge  127.127.28.1 refid PPS

Both nptd and gpsd look at the first 2 segments:

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status      
0x4e545030 0          root       600        96         2                       
0x4e545031 32769      root       600        96         2                       
0x4e545032 65538      root       666        96         1                       
0x4e545033 98307      root       666        96         1                       
0x47505344 131076     root       666        8240       1                       

The PPS seems to be seen by gpsd:
root at hoei:/home/folkert# strace -fp 27872 2>&1 | grep ioctl
...
[pid 27873] ioctl(9, PPS_FETCH, 0x7f1e63cc9d00) = 0

and the NMEA sentences are processed correctly:

x127.127.28.0    .NMEA.           0 l   10   16  377    0.000  -275.55 4.421

but the pps isn't:

 127.127.28.1    .PPS.            0 l    -   16    0    0.000    0.000 0.000

Anyone any idea?


Folkert van Heusden

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