Yo Ilia! On Thu, 20 Oct 2016 07:52:10 +0000 Ilia Platone <i...@iliaplatone.com> wrote:
> I quickly read the gpsd howto and it explains what I want to do using > kpps on a raspberry. From there I can see a typical accuracy of 1uS, > but the informations of the live graphs page are precise down to the > ns: are these averaged? Well, that is a complicated question. The graphs are directly from the ntpd logs. No modification to the data except scaling. But ntpd itself is sort of a big PLL. Also the way ntpd handles PPS is somewhat complicated. There is an algorithm for ignoring outlier pulses, and the accepted puless are averaged in the mipoll interval before being logged or input into the PLL But, bottom line, you can pretty much expect the RasPi sysclock to be stable and accurate, to one standard deviation of better than 1 µs. 90% of the time, to better than 2 µs. Better than 5.5 µs for 98% of the time. RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 g...@rellim.com Tel:+1 541 382 8588
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