[ntp:questions] NTP, GPSD & PPS

David Taylor david-taylor at blueyonder.co.uk.invalid
Sat Dec 13 07:52:03 UTC 2014


On 10/12/2014 12:39, Miroslav Lichvar wrote:
> On Wed, Dec 10, 2014 at 11:50:22AM +0000, David Taylor wrote:
>> With -D 4 I get a list of devices ending with "PPS", but presumably that is
>> not the same as "KPPS"?
>
> In gpsd the PPS without K is the userspace timestamping. With kernel
> timestamping the log looks like this:
>
> gpsd:PROG: PPS edge: 1, cycle: 1000000 uSec, duration:  799998 uSec @ 1418214654.000007216
> gpsd:INFO: PPS hooks called with accepted 1418214653.999999223 offset 0.000000777
> gpsd:PROG: PPS edge accepted 1418214653.999999223 offset 0.000000777
> gpsd:PROG: KPPS assert 1418214653.999999223, sequence: 73 - clear  1418214654.200000573, sequence: 73
> gpsd:PROG: KPPS data: using clear
> gpsd:PROG: KPPS cycle:  999999 uSec, duration:  200001 uSec @ 1418214654.200000573
>
>> I did try an apt-get first to update gpsd but it
>> seems I have the most recent available.  It seems I have 3.6.  Do I need a
>> development version or...?
>
> The kernel PPS support was added in 3.0 or so, but gpsd needs to be
> compiled with the timepps.h header, similarly to ntpd for the ATOM and
> other drivers. Also, some gpsd versions had bugs in the PPS/KPPS
> support and I'm not sure if 3.6 was a good or bad. The latest version
> - 3.11 is working well for me, 3.10 was not.

Many thanks, Miroslav.

For some reason, gpsd seems to be stuck at a lower release for the 
Raspberry Pi version of Debian, so I will have a go at recompiling it 
once I can find the right instructions!  That's if there's no 
development version I can get with apt-get, and I haven't found out how 
to do that yet.  Still learning!
-- 
Cheers,
David
Web: http://www.satsignal.eu



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