[time-nuts] Thought experiment on a low cost timing board

John Pettitt jpp at cloudview.com
Thu Feb 23 11:07:41 EST 2006

I asked a couple of weeks back about getting an ICS525 with an eye to
making one of my Soekris 4801's more stable by using the 5Mhz from my
GPS-DC to generate the clock.  However I have a "better idea" that I'd
like to run past the group for comment.

I read the work phk did (http://phk.freebsd.dk/soekris/pps/) and came up
with the following product idea.   

The spec:

PCI 3.3v board with:
    10Mhz OCXO (provision for external clock source?)
    Uart (serial is an endangered on many PC's)
    Free running counter driven from the OCXO and readable by PC
    inputs to latch the counter (how many?) with the latched result also
readable (for PPS)
This will let me turn any PC into a stable clock using cheap gps (eg
GPS18LVC) that has a PPS output.   However the real win comes if I can
figure out  how to discipline the OCXO using an external 1PPS input - if
I can do that then I can provide a stable X MHz out (where X may be
programmable using the ICS525) making the board very useful for lots of

So does the basic idea make sense?  More importantly can somebody opine
on if it's possible to use a 1PPS to discipline an OCXO (I've seen
designs to it from a 10KHz signal for sale on eBay)) -

Now if this actually looks feasible I may pay somebody to design it and
build a a few  to sell on ebay.


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