To use one or more control surfaces with Logic Pro, you will need:
An installed, authorized copy of Logic Pro
For USB- or FireWire-equipped devices (such as a Yamaha 01X), an available USB or FireWire port. Ideally, this should be a direct USB/FireWire connection with the computer, rather than via a USB/FireWire hub. Refer to the documentation provided by the manufacturer of your control surface.
For devices that are only equipped with MIDI ports (such as a Mackie Control), a MIDI interface with free MIDI input and output ports for each device. For example, if you’re using a MIDI interface with 8 MIDI input ports and 8 MIDI output ports—with one Mackie Control and one Mackie Control XT unit—you will need to use two of the interface’s MIDI In ports, and two of its MIDI Out ports.
An installed driver (if required by your control surface) that is supported by the operating system you are using on your computer
Important: Your MIDI interface must feature driver software that supports SysEx communication. Consult the documentation that shipped with your MIDI interface (or MIDI interface drivers).
The number of devices that can be used simultaneously depends on the number of free ports of the appropriate type (USB, FireWire, or other) available on your system. In a standard setup, you can use a single control surface, or one accompanied by one or more expansion devices. You can also create control surface groups, as described in Creating Control Surface Groups.
Using multiple control surfaces allows you to control more tracks and channels, effects, and other parameters simultaneously. For example, the Mackie Control XT devices are basically identical to the channel strip section (fader, V-Pot, and LCD) of the main Mackie Control unit. The Mackie C4 features a number of V-Pots, but no faders. You can add as many XT, C4, or other control surface devices as you wish to your system, provided that enough free MIDI In and Out (or USB or other suitable) ports are available.