This is the August 12, 2009 Adafruit Motor shield firmware with basic Microstepping support. Works with all Arduinos and the Mega For more information on the shield, please visit http://www.ladyada.net/make/mshield/ To install, click DOWNLOAD SOURCE in the top right corner, and see our tutorial at http://www.ladyada.net/library/arduino/libraries.html on Arduino Library installation