Well, how do you normally do it? Have you used it? Don't you have to make a g-code file first? Where do you put or get gcode in grbl?
My assumption is you make a g-code file, put it on a flash card, and grbl can open the file, from on the controller, but I'm not clear on how grbl knows what file to open or if it involves streaming data or commands to grbl, or if it is hardwired to any certain file input path.
I got a couple of months experience a couple months ago with arduino, related to cnc, then got sidetracked rebuilding my store web site, before I got to try grbl, I was working on controlling mach3 with arduino and tft screens.
Maybe we could get a discussion going on this, and figure it out. I definitely want to know more myself, and see how grbl works, it seems like a good alternative to mach3 if you ask me....
Got any pictures? or specs? or stories? about it? I'd love to know more about what you're doing with it and how it's going.
I'll help any way I can. I'm not sure if your question is about how to make g-code or how to transfer g-code files to arduino or something else.