The can be possible to catch a Tx Gcode command asking for change extruder, so Octoprint trigger an Gcode script to retract then send outputs in binary I guest so I can takea multiplexer for change the extruder withoout a MMU unit, something like this:
inside the GCODE
- Octoprint trigger a Retract GCode command for n mm
- Output GPIO27,17,22 101
- External multiplexer circuit take the raspberry output and select the extruder cabling coming from the printer and change to another extruder
- Octorpint trigger a Extrude (for advance filament into nozzle)
so the result is a filament change having a marlin config for a single extruder and single nozzle. (without MMU unit)
with 3 outputs we can use up to 8 extruders.