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

John Ackermann N8UR jra at febo.com
Fri Feb 24 06:07:17 EST 2006

The TAPR Reflock II board (designed by Luis Cupido) is shipping now and 
will discipline a VCXO to 1pps, or to other frequencies.  I'm traveling 
now and don't have the exact URL handy, but www.tapr.org will have a link.

I've spoken with Luis about using the Reflock to synthesize an 
appropriate frequency to replace a PC clock, and he thinks that's 
possible, but I don't think he's followed up on that yet (indication of 
desire for it might prod him along).  The idea is that the CPLD on the 
Reflock would do the 1pps discipline, as well as synthesize the desired 
output frequency from the 10MHz source.


John Pettitt wrote:
> 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
> things.
> 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.
> John
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