[ntp:questions] Re: Linux PPS triggering with NMEA

Bjorn Gabrielsson bg at lysator.liu.se
Tue May 10 00:36:54 UTC 2005

"David Schwartz" <davids at webmaster.com> writes:

> "Bjorn Gabrielsson" <bg at lysator.liu.se> wrote in message 
> news:m31x8gowh0.fsf at lysator.liu.se...
> > "David Schwartz" <davids at webmaster.com> writes:
> >>     No. But unless you have some specialized hardware, you're just 
> >> kidding
> >> yourself if you think you can get more than that. Even with a PPS input
> >> accurate to 200nS and the PPS kernel patches, accuracy is still only 
> >> about 3
> >> microseconds.
> > Did you reread  http://phk.freebsd.dk/soekris/pps/ lately?
>     A rubidium frequency standard qualified as "specialized hardware" in my 
> book.
>     DS

You are missing the point. The Rb is there as part of the test special
setup. The Rb has nothing to do with the timestamping capability the
soekris board, its there to give a truth to evaluate the timestamps

"we should be able to timestamp to around a quarter of a microsecond."

"...the remaining 98% of the samples are inside a band 260 nanoseconds
wide ([-118..142]) which is in excellent agreement with our


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