I see what you're saying... and thankfully right now there's no readbacks being done.

The fan controller seems to work ok with and without the scope probes with 100K.

In the future however, hopefully no one will ever need to do actual reads on the bus, because then the rise-time wouldn't be enough to clear a '1' at the current clock rate unless some big delays are added between every clock pulse.

Personally, I'm changing mine back to 5.1K so that it could actually operate to specifications based on a 400KHz clock.

I don't have warm fuzzies about the current 100K resistor.

Thanks for all your help though... simply fabulous.

If you want, post that last PNG I sent you if everyone else would like to see.

Ciao,

-Ben