Re: pulse-per-second API status

[Jochen Kunz <jkunz%unixag-kl.fh-kl.de@localhost>]

On Fri, 1 Nov 2013 14:48:51 -0400
"Terry Moore" <tmm%mcci.com@localhost> wrote:

> But using a serial port handshaking line over an emulated com port over USB
> is not likely to be terribly wonderful. Long-term accuracy (tick count)
> probably no problem, but jitter.... it will depend on how that's filtered.
That's the key. Once I did a DCF77 decoder in an Atmel AVR. (DCF77 is a
radio station that sends a PPS signal plus BCD encoded absolute time.)
The cheap radio reciver had a considerably jitter. So I simply summed up
the PPS count from the receiver and the tics from the local quarz clock
over the period of hours. Some ms of jitter are negligible compared to
several hours. Using this I was able to calibrate the local quarz
oscilator down into the ppm range. I.e. I was able to notice the
temperature drift of the local quarz oscilator.

If you know what to do, even a jitterish PPS signal can be of good use.
-- 


\end{Jochen}

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