Before we descend in to the nitty gritty I think we need the big picture.

If the Raspberry video is interrupt unfriendly, how do we get a screen display?

I use a Win7 laptop and wrote software to drive my mills through a USB, but that requires Visual Studio and makes the cheap solution expensive.

If we add a Linux PC to get the free compiler and upload the Gcode, it has a display and the Raspberry display would seem irrelevant.