The site limits attached images to 800x800 so I had to scale it down to fit. I can email you the original if you post your address.
There are a few bipolar/unipolar driver circuits posted on cnczone that are fairly simple to make.
We have one based on the LMD18245 3amp driver chip that is microstepping capable. Bare PCB board, schematic and source code are available on my website. A bit more expensive to put together but the performance is much better then the typical unipolar half/full step drive circuits found on the web.
Jim
www.embeddedtronics.com