GCode is the generic name for a control language for CNC (or Reprap) machines. It is a way for you to tell the machine to move to various points at a desired speed, control the spindle speed, turn on and off various coolants, and all sorts of other things. It is fairly standard, and is a useful tool.
ReplicatorG attempts to follow GCode as closely as possible. Since it is a funky, and very old language, it has evolved into many things. It is hard to find a clear, concise guide, so we have attempted to implement things the best we can by sampling and averaging from the best implementations.
Here are some of the guides we have been working from:
- TurboCNC - a solid CNC control software.
- LinuxCNC - they have a pretty good reference.
- Wikipedia - they also have a pretty decent GCode page.
The motherboard inside the Makerbot uses a Sanguino, a relatively small microcontroller that even includes a G-Code interpreter. However, ReplicatorG sends a preprocessed and abbreviated code called S3G, Sanguino3G.