On Sun, Sep 14, 2014 at 4:29 AM, Andrew Rodland <[email protected]> wrote: > My clock is quantized at 10MHz, so you wouldn't expect better than > 100ns accuracy. But I added -50ns to the offset in software, making it > zero in on the edge where the offset is 0 counts 50% of the time and > -1 count the other 50%. (Dithering provided by noise in the system and > the Resolution-T's own sawtooth). This seems to have worked better > than expected.
I'm in the middle of measuring a free-run with the control loop disabled and I realized that this explanation is pretty well mistaken. The thing is, even though I can only *measure* time (the PPS offset, or NTP timestamps) in multiples of the 10MHz clock, my PPS *output* is actually quantized by the 84MHz crystal clock on the Due. +/- 1 cycle at 84MHz = ~24ns, and that agrees much better with the noise I see at very short times. Andrew _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
