[ntp:questions] Re: Clock type 30 invalid?

David L. Mills mills at udel.edu
Sat Jan 24 06:12:52 UTC 2004


Hal,

Wow, are we all confused, especially me. The atom driver expects the PPS
timestamp and the timecode timestamp to be within 128 ms, which is
appropriate for many GPS radios, but not all. The NMEA radios do an evil
thing; they produce a timecode at some random time within the second and
then expect the PPS to latch the exact second epoch. As the atom driver
does not do this, those GPS drivers that operate like NMEA usually do
their own thing using PPSAPI directly. I would really hope NMEA is NMEA
is NMEA and sll the clocks that support this protocol use the same
driver.

Dave

Hal Murray wrote:
> 
> >Eeeeek! I should have said the NMEA clocks don't use the atom driver;
> >but, they do use the PPSAPI and require the timepps.h file. Sorry about
> >that; it is late and the birds and cats are asleep.
> 
> Now I'm doubly coufused.
> 
> My NMEA gear is using 127.127.20.1 yet the subject of this thread
> is type 30.  Are we talking about the same thing?
> 
> My NMEA setup is using the Atom/PPS driver - 127.127.22.1.
> I think there is a way to get the NMEA driver to handoff the PPS
> processing to the kernel.  This gets logging and/or I don't understand
> the rest of the tradeoffs.
> 
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