Weiss has written up documentation on his Stepper motor controller:
The reason for this project was my frustration over how much it takes to just test a simple stepper motor. To test a stepper motor you usually need some kind of MCU most likely a Arduino, your breadboard, cables, some kind of driver and other components. When you got all that assembled you still need to write and upload some code to run the driver, but before you can do that you also need to find your USB cable and if the code doesn’t work you have to debug it. All this can easily take an hour but with the Easy Stepper you just plug in your stepper motor and whatever power supply you have and you are ready to go.
Via the forum.