Listening and sending gcode to printer with microcontroller
I'm working with a Prusa MK2 with 4 extruders that I'm planning a mod to in order to improve it's multi material functionality.
Essentially, what I need to be able to do is have a separate micro controller of some kind listening to the printer, and when the printer is changing materials it will send the pause gcode to the printer, perform some separate actions involving a servo and motor, then send the gcode to have the printer resume the print. I want to be able to do this without needing to have the printer connected to a computer so it can be more versatile and independent.
I feel like none of this should be too complicated, but I'm having trouble finding anything very helpful or definitive on how to go about doing this. Does anyone have any thoughts or advice?