The controller can accept commands on the UART and to make the required number of steps in the right direction. The direction of rotation and the required number of steps given by a single command. For example, to make the 300 steps to one side sends a command 300. If you want to rotate in the opposite direction, sending "-"and the number of steps, it's simple. Also provides for rotation of the engine buttons.
to view go here http://www.youtube.com/watch?v=ceC7vqkssWo and http://www.youtube.com/watch?v=JTbJFN6Hsy4&feature=channel_video_title
more information http://avrproject.ru/
When you turn the controller generates a COM-port message about entering the direction of motion (+ or -) and the number of steps. Send the necessary command and the controller will rotate the motor shaft, once committed the required number of steps, the controller will issue the command "OK!" and again will give a command to input data.
buttons and pins