libmackie

A C library for the Mackie Control (MCU) protocol that motorised MIDI control surfaces such as the Behringer X-Touch speak: encoders and decoders for motor faders, buttons and their lamps, V-Pots and their LED rings, the jog wheel, meters, scribble strips and their backlights, the seven-segment displays and the host-connection handshake.

It is a codec and nothing else. Every function is pure, over caller memory: no MIDI port, no clock, no thread, no allocation. The host already owns a MIDI transport (ALSA sequencer, raw MIDI, a DAW's own) and carries the bytes; libmackie says what they are.

Where it sits

libmackie is the wire layer under a surface behaviour layer (motor policy, touch, banking, repaint) that is shared by MIDI surfaces and by DigiNet desks such as the Digidesign Control|24 (libdiginet). MIDI bytes never cross into that layer: libmackie encodes and decodes them, and the host carries them. The design is on libdiginet#29.

The control map

Which note, CC or pitch-bend channel each control sits on is the surface's, not the protocol's. The host fills a struct mackie_map from its own surface profile, the one source of every address, and every encoder and decoder reads it. libmackie keeps no second table of addresses beside the profile; mackie_map_check() refuses a map it cannot use, whole.

Provenance

The codec is a port of a TypeScript MCU module (the X-Touch adapter's mcu.ts) that drives X-Touches in production. It is held to that module byte for byte: tools/gen-goldens.mjs ran every TypeScript encoder and decoder over a set of inputs and wrote what they returned into tests/golden/mcu_golden.h, and tests/test_golden.c checks every C encoder and decoder against it. The host-connection handshake is pinned to an exchange captured live on an X-Touch (firmware V1.22).

Building and testing: BUILDING.md.

Licence

GPL-3.0-or-later. See LICENSE.