> Your goal should be Arm boards that are within 1 second per day on
the
> system clock. I would imagine, with the hardware you have, you
could
> achive that with a little creativity, it is a matter of software.
1 second per day is beyond what can be done with today's common
crystal oscillator technology. You would have to go with expensive
temperature compensated crystal oscillators or rubidium
oscillators. One may be able to calibrate a single unit at a
constant temp better than 50 PPM, but crystals also drift with age--
it would be impossible for a manufacturer of hardware to guarantee a
more accurate clock than that of the crystal manufacturer and
crystal manufacturers say 50 PPM.
The timing drift in this instance is excacerbated by software,
specifically the Linux kernel and its legacy of a 100Hz tick rate.
We cannot take ownership of all Linux problems just like one cannot
expect to be able to contact the USB mouse manufacturer when a mouse
pointer locks up on a PC screen. We fix what we can, but we can't
get any better accuracy currently with Linux. I believe another one
of our customers in this forum actually use the TS-7200 in a NTP
server product they designed-- you may want to contact them for any
patches they may have made to the kernel.
GPS units have very precise timing. We have a PC104 daughterboard
designed for a customer that includes a GPS unit that extracts an
extremely precise 1Hz and 10000Hz signal from the air. This
solution would still be much cheaper than a rubidium oscillator.
//Jesse Off
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