I am building a large printer that needs 3 independent Z-stepper motors that will home with a BLTouch and 2 Y-stepper motors with an endstop for each side.
I can use the
E1 for the extra Y and I plan on adding two external stepper drivers for the two extra Z-stepper.
There should be 8 free pins in AUX-2 to add the two stepper drivers. I purchased some stepper expansion boards and will be using the same A4988 stepper drivers as the rest of the motors.
The hard part is figuring out how to modify Marlin to recognize the new steppers. I also need to get it to do a 2 stepper Y-homing sequence.