Disable stepper driver
How are you driving the other +/- inputs? Drive MF the same.
These inputs are typically meant to be driven with an open collector output. A logic output will usually work also if VCC is the same as a logic high.
It appears that active = LED On. If you put 5V on MF+ and ground MF- is should disable the stepper.



simulate this circuit &ndash; Schematic created using CircuitLab