[time-nuts] looking for good description/generalized model for time adjustments
Christian Vogel
vogelchr at vogel.cx
Wed Jul 29 18:50:54 UTC 2009
Hi Lux,
> The real problem is that the "master" clock might be a crummy 50ppm XO, and all us "slaves" all have TCXOs that are good to a few ppm. It's almost the inverse problem from disciplining a XO with GPS.
>
I have the impression that you are confused by your own weird
terminology ;-). If you have a rather good clock yourself, and want to
somehow characterize external events with their own sketchy time-of-day
estimation, then please don't call this cheap thing the "master".
Just let your internal clock ("precise") run undisturbed and capture the
precise time for all the external events received from the "cheap"
outside machines. Then timestamp a number of external/internal events
and calculate the average relative external clock frequency. Filter the
last N events and use the relative frequencies to extrapolate events to
be expected in the future. It's basically just a PLL done in software.
Without telling us some details, noone here will be able to give you
real advice, I think...
Chris
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