[ntp:questions] ntpd connect gpsd shared memory driver

A C agcarver+ntp at acarver.net
Tue Jun 18 07:22:11 UTC 2013


On 6/17/2013 16:55, Richard Cagley wrote:
> Based on poor luck with ntpd/pps, I'm trying to have ntpd use the shared
> memory driver provided by gpsd. Do I need to give a special flag to
> configure for ntp to tell it to build in support for the shared memory
> driver?
>
> Using this for my ntp.conf
> ---
> server 127.127.28.0 minpoll 4
> fudge 127.127.28.0 refid NMEA
> ---
> I get nothing
> / # ntpq -p
>       remote           refid      st t when poll reach   delay   offset
>   jitter
> ==============================================================================
>   SHM(0)          .NMEA.           0 l    -   16    0    0.000    0.000
> 0.000
>
> but, gpsd is patiently waiting for something to happen...
> / # gpsd -b -N -D5 /dev/ttyO0

You need -n (lower case N) to force gpsd to start collecting data 
automatically.  It normally waits for something to connect to its TCP 
port and enable data collection (the WATCH command as you discovered). 
If you start with just:

gpsd -bn /dev/ttyO0

You'll find the SHMs are populated after a few seconds (once gpsd syncs 
with the data stream from the receiver).



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