[time-nuts] thunderbolt for ntpd or gpsd

Tim Cwik timenuts at stnhbr.com
Sun Jun 15 17:57:25 EDT 2008


Wayne Knowles wrote:
> Tim, Chris,
>
> Over a month ago I experimented with getting GPSD and the Tunderbolt working 
> together.
> I quickly added support for the missing TSIP packet types, and was able to get 
> xgps to display lat, long, time  and constellation status.   I did manage to 
> get NTP to work, have not invested the time into getting the 1PPS signal 
> working under FreeBSD yet.
>
> I have attached my patches against the gpsd source repository.   Note that I 
> did not invest much time understanding the internals of gpsd beforehand so 
> some aspects may not be fully implemented.
>
>   
Thanks Wayne and Chris and Chris.

I have discovered the even though cgps does not report position or time 
using the Thunderbolt, the stock gpsd is getting enough timing data to 
update ntp. Gpsd is selected as the sys.peer with a jitter of about .8. 
It looks like the PPS pulse is too narrow to be detected on DCD, I am 
going to investigate a pulse stretcher available from TAPR 
http://tapr.org/kits_fatpps.html and will see if that helps. FWIW, 
Centos 5.1 selinux allows gpsd to update the ntp shared memory segment 
out of the box.


73,




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