[time-nuts] thunderbolt for ntpd or gpsd

Scott Mace smace at intt.net
Thu Aug 14 22:00:46 EDT 2008

I found that on the two FatPPS units I have, pin 2 on the female DE-9 connector
is tied to the DC-IN. This was causing noise from the thunderbolt RS-232
TX to get into the PPS output.  It basically made it totally unusable.
I removed R4 since I use DTR for power and it works perfectly.


Tim Cwik wrote:
> 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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