The data I had found for Cat 5 was 17pf/ft, and yes 400pf max (from =20
Philips I2C bus spec).  However, I'm running this at ~10kHz now, and =20
that will go up to ~15kHz soon.  SO that should be okay, but I just =20
need minimize noise now.

Cheers,
-Neil.


Quoting John Coppens <john@jcoppens.com>:

> 15ft - about 4.5 meters? I believe that is quite near (or over) the
> limits. The main limitation is 400 pF on the SCK and SDA lines, at the
> lowest speed. Estimating 1 pF per centimeter, you will have (at
> least) 450 pF there.
>
> I2C is just not designed for such a distance.
>
> John




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