Hi, y’all. I was bit by a bug to play with grbl, and found that there was a grbl-Mega project over on github already. The only problem with it is that trying to run the dual motors off of E0 and E1 would not be easy (or even possible without software or hardware hacking). I initially looked at just making E0 and E1 be copies of X and Y but there’s a whole lot of changes that would be needed. More than I would care to do just to play around.
In order to scratch my grbl itch, I jumped into my schematic program and drew up a little board to go between the RAMPS and the X and Y drivers. It has a place for a second driver, and a little circuit to invert the direction pin going over there. Since it covers up the regular motor pins, the two motor cables plug into that board as well. I guess the transistor inversion thing isn’t really needed (just plug the 2nd wires in backwards) but my OCD would know it’s backwards, even if it was hidden under the table.
Sure, hardware costs money, but it only took a few minutes to do, and I have the parts already. If anyone else is interested and can deal with a couple of surface mount resistors and a transistor, I shared the project on Osh Park at https://www.oshpark.com/shared_projects/WIHfUqpZ and the github link to that fork of grbl is at GitHub - gnea/grbl-Mega: An open source, embedded, high performance g-code-parser and CNC milling controller written in optimized C that will run on an Arduino Mega2560