Hi all, David here.
First a confession, I have never attempted to build a circuit board of any kind before so I have been struggling to get this project started.
Sheer bull-headed determination (or the inability to recognize my own limitations) has gotten me to the point where I have a working system. This is a Mega2560 based DIY board that does not include the ST4 connection, just the DEC and RA controls.
After finding this project and deciding to try and build it I was faced with problem that I have no experience in this sort of electronics. I can recognize the basic components on a schematic diagram but had no idea how to convert that to an actual working circuit. Oh, and did I mention that I'm cheap? Even if I had wanted to buy a pre-built unit from Tom, the current hiatus in availability meant DIY was my alternate choice.
I won't walk you through the process that got me to a working circuit because it unfolded over several weeks. What I do want to do is contribute something back to the project. So, what I'm attaching here is a fritzing file of the breadboard layout that I used to get a working circuit. Maybe I just didn't search hard enough but I was unable to find something like this to help me make the leap from schematic to working circuit. Hopefully this will be of use to others.
Please note that I cannot confirm the "correctness" of this breadboard. All I can say is that it makes the motors turn on my EQ5 mount and responds correctly under EQMOD.
All the best and many thanks to Tom for this project.
Fritzing File (on dropbox)