Running the Simple Pro via a USB cable:
Please go to this link for more details: https://github.com/abdrumm/printrbot-docs , right now there are broken links but I am working on getting the content of those. Some of that content may be found in other documents at the github link.
In summary it has info on connecting the Simple Pro with a USB cable. You must have the computer powered up first, then plug the USB cable into the computer from the Simple Pro, then turn SImple Pro power on. There is a test in the power up code on the Simple Pro that checks for a USB cable only then. The LCD screen is useless, don't use it for anything. The hot end height needs special code to adjust it. No settings are saved between resets, so the start code needs to be executed each time.
I found this worked just fine with Repetier-Host V2.1.1 and Slic3r without any special start code. Only the hot end height is a little off.
As we get more information it will be posted here.