Hey Festdewalkita,
here I link you to a typical closed-loop stepper driver and its Manual (PDF). As you can see on the diagram,
to drive such a closed-looop stepper driver, the CNC Controller needs the step, direction and enable lines to control the motor. These lines exist inside the Onefinity Controller (they go into the TI DRV8711 stepper drivers) but are not accessible from the outside. The Buildbotics Controller in its recent version now makes these lines accessible with its 15-pin auxiliary I/O port, so that you can connect closed-loop steppers.
See also here.