How do I switch a motor to the spare stepper driver output?

With the machine turned off.

Plug the motor into Drive 4 on this diagram: https://d17kynu4zpq5hy.cloudfront.net/ig...

Turn the machine on.

On the drive number, you want to switch below change the P value to 4.

; Configure Drives

M569 P0 S0 ; Drive 0 goes forwards

M569 P1 S1 ; Drive 1 goes forwards

M569 P2 S0 ; Drive 2 goes forwards

M569 P3 S1 ; Drive 3 goes forwards

For example, if we want to change the X-Axis, it would become:

; Configure Drives

M569 P4 S0 ; Drive 0 goes forwards

M569 P1 S1 ; Drive 1 goes forwards

M569 P2 S0 ; Drive 2 goes forwards

M569 P3 S1 ; Drive 3 goes forwards

On the drive number, again you want to switch below change the number to 4 for the correct axis.

M584 X0 Y1:3 Z2 ; Apply drive mapping to axes

Again in the example of the X-Axis it will become:

M584 X4 Y1:3 Z2 ; Apply drive mapping to axes

Restart the board.