I'm using an arduino in a stompbox to control an analog circuit via an optoisolator. I do not want the analog and digital circuits to share ground since I've found that introduces noise even with extensive filtering. However, I still want to be able to run everything off of a single 9v power supply.
First of all, I assume I'll need one of these on the Arduino side: http://www.sparkfun.com/commerce/product_info.php?products_id=107.
Second, how do I keep the grounds seperated? Obviously, all of the circuits wired to a multi-pedal power supply are not sharing ground, but is there anyway to do this without adding a heavy and bulky transformer to the box?