I’d like to control a Rainbowduino board and Seeedstudio LED cube kit from a computer, without an Arduino board. Is this possible using techniques similar to what the mtXcontrol program does to control an LED matrix? If so, what cables would I need to purchase?
Yes, the easiest way is to use the UARTSB from Seedstudio. It plugs into the Rainbowduino and gives you a USB serial connection to the board. You can control it using techniques from mtxcontrol, or the MeggyJr-compatible library (code.google.com/p/rainbowmcompat/) has some serial port control examples.