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Arduino library for MIDI control and input.
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README.md

Control Surface

An Arduino library for MIDI control surfaces (input and output).

UNDER CONSTRUCTION

Should not be considered stable. API is might change in the near future.

Overview

This library turns your Arduino-compatible board into a MIDI control surface.

Just connect up some push buttons, potentiometers, LEDs ... and declare them in your code.

Multiple different MIDI interfaces are supported: MIDI over USB, Serial MIDI (e.g. 5-pin DIN MIDI), Debug MIDI (prints out the messages in a readable format, and allows you to input text based messages), MIDI over Bluetooth LE (experimental).

For MIDI output, you can use push buttons, toggle switches, potentiometers, faders, rotary encoders, etc.

All digital inputs are debounced, and all analog inputs are filtered using digital filters and hysteresis. This results in high accuracy without noise, without introducing latency.

These can be used to send MIDI notes, Control Changes, Pitch Bends, Program/Patch changes, etc.

For MIDI input, you can use LEDs to display the state of different settings, to display the audio level of each channel (VU meters), the positions of knobs (V-Pot LED rings), etc.
You can also add an OLED display (e.g. SSD1306) to display a nice overview of which channels are set to mute or solo, display the time cursor, VU meters, etc. Bitmaps with play, mute, solo, record buttons, and others are included.

A large portion of the Mackie Control Universal protocol is implemented.

All controls can be arranged in banks: e.g. if you have only 4 physical volume faders, you can add them to a bank, and then you can control 8 channels (or more) by changing the bank setting.

Apart from banks and bank selectors, you can also add transposers to change the key of your notes, for example.

In order to save some IO pins, the library natively supports Shift Registers (e.g. 74HC595) and multiplexers (e.g. 74HC4051 or 74HC4067).

If you are using a Teensy 3.x, you can use it as a USB audio interface. Just add an I²S DAC (e.g. PCM5102), and 5 lines of code, and you can start playing audio through your Teensy.
You can also add volume controls and VU meters for these audio connections.

Thanks to the structure of the library, you can easily add your own MIDI or display elements, using some minimal, high level code. All low level stuff is completely reusable (e.g. all MIDI operations, debouncing switches, filtering analog inputs, and so on).

The Control Surface vs. The MIDI Controller library

You might already have found my other Arduino MIDI library, MIDI Controller, and are wondering which one you should use for your project.

First, some background:
I first started working on the MIDI Controller library way back in 2015, and it evolved a lot early on. The library seemed to be pretty popular, and it worked pretty well, so I couldn't just push breaking changes every couple of months.
Many people requested support for MIDI input, and I liked experimenting with it as well. The main problem was that the overall architecture of the library needed a complete overhaul in order to add MIDI input support. Since I didn't know if the MIDI input was going to work out, and I didn't want to break compatibility with older versions of the library, I decided to fork it: Control Surface was born.
At the moment, I consider the MIDI Controller library "complete". I won't be adding any groundbreaking new features, but I will still be fixing bugs and providing support.
Control Surface, on the other hand, is where the active development takes place.

The main difference between the two libraries is that Control Surface has much more features. MIDI Controller has everything you need for a working MIDI controller with potentiometers, push buttons, rotary encoders, etc., while Control Surface supports all of that, plus MIDI input, LEDs, VU meters, OLED displays, MIDI over Bluetooth, Audio over USB, etc.
Another major difference is the documentation and tests. Control Surface tries to provide better documentation using Doxygen, and it has many unit tests to make sure I don't introduce any bugs.

For a new project, I would recommend Control Surface, because I think it has some great features compared to MIDI Controller.
The only caveat is that this library is still under development. Master should always be relatively stable, but I might change the API of some parts of the library for future releases if necessary.
Another thing is that not everything is implemented yet, and many features are not yet fully documented. If you have a specific feature request that is not yet fully implemented, feel free to open an issue, so I know where to focus on first.

Work in progress

  • Adding support for motorized faders
  • Cleaning up the display code
  • Cleaning up the MIDI over Bluetooth LE code
  • Finish support for MIDI over USB cable numbers
  • Adding more tests (currently at over 170 unit tests)
  • Adding more examples and adding comments to existing examples
  • Finishing the documentation

Getting Started

See the Getting Started document to get started using the library.

Documentation

The automatically generated Doxygen documentation for this library can be found here. (incomplete)

Building and running the tests

For help compiling and running the tests, see Tests.md.

Known problems

When compiling without LTO (Link Time Optimization) and -Os (optimize for size), GCC will produce a linker error (Undefined reference to ...).
This is normal, and it helps me to find other errors. I will eventually fix it when I release a stable version of the library.

For now, just enable LTO, or choose a different optimization option.

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