Operating a Shared Extruder with a Y-switch Between Steppers and Hotend
I recently setup my printer for a shared hotend fed from two steppers through a Y connection. I setup the firmware for a shared extruder, and that works properly; it gives me control of two steppers and a single hotend with one heater.
I setup the firmware for G10/G11 firmware extraction, and that works correctly when I use either stepper during a print, or switch steppers with a manual pause (or M600 command) followed by a tool-change command (T#).
As part of the firmware configuration, I also defined the retraction/unretraction lengths required by the Y-device during a tool change, but I do not know how to trigger the firmware to cause the current stepper to retract, and the next stepper to advance.
I see that there is a long-extract/retract command in the G10/11 commands, and I've also seen placeholder variables such as previous and next used in commands. I suspect some G-Code belongs in the printer profile when a tool is changed, but I don't know the syntax and how to use them. If there is a document that defines how this works, please point me in that direction.