hi!

does anyone know a good way to use multiplexing with an arduinoboard?
my goal is to make a controller for my synthesizer in pd with lots of knobs and buttons.

in this video the guy seems to have done exactly that:

/niklas

I think what you want to do is actually demultiplexing?

http://www.arduino.cc/playground/Main/InterfacingWithHardware#Input

The arduino playground has info about digital multi/demulti chips.
I'm interested in this as well, with arduino and a key scanning matrix, like in keypads and keyboards, i believe you square the number of inputs.

check it out;
http://www.dribin.org/dave/keyboard/one_html/

Let us know how it goes.

see this

Instead of Arduino. Try to look at this:

http://www.u-hid.com/home/index.php

It might help you.