[time-nuts] thunderbolt for ntpd or gpsd
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
>> 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.
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