This project contains hardware and firmware for a 4x4 MIDI merger/splitter patchbay based on an Arduino MEGA 2560. It has 4 MIDI inputs and 4 MIDI outputs. In the simplest case, it will merge all 4 inputs and then split the combined MIDI stream across the 4 outputs. However the routing is controlled by the firmware so you can configure it to patch any combination of inputs into any of the outputs.
The hardware directory contains Eagle schematics, board designs and Gerber files for the following modules.
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MIDI-Patchbay-Shield is a shield for an Arduino MEGA 2560 that provides 4 MIDI inputs, 4 MIDI outputs and connectors for interfacing to the MIDI-Patchbay-Display board. It also contains connectors for accessing 8 analog pins and 8 digital pins for further expansion. This is the main board that you need to build.
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MIDI-Patchbay-Display is a board for mounting a 16x2 LCD display and two RGB rotary encoders. This is an optional extra. You can build a fully functioning MIDI merger/splitter without it.
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MIDI-Patchbay-Simple is the predecessor of the MIDI-Patchbay-Shield. This is a reduced size shield for the Arduino MEGA 2560 that only has 4 MIDI inputs and 4 MIDI outputs, along with the relevant circuitry to support it. If you just want a simple MIDI merger/splitter without any extra frills then this is the simplest option as an alternative to the above.
The boards use surface mount (SMD) components, but nothing smaller than 0805 (that's 2012 in metric: approximately 2.0mm x 1.25mm) which can easily be soldered by hand. It's really not much harder than through-hole components, so don't be put off if you haven't used SMD before. But you will need to invest in some tweezers and a magnifier/light unit to help you see what you're doing. And of course, a decent soldering iron.
The firmware directory contains the source code for the firmware that powers the boards listed above. It is built around the Arduino MIDI Library by Forty Seven Effects.
- MIDI-Patchbay-Simple.ino implements a simple 4x4 MIDI patchbay that merges all four MIDI inputs and duplicates them across all four MIDI outputs. It is specifically for use with the basic MIDI-Patchbay-Simple board, but can also be used with the more advanced MIDI-Patchbay-Shield if you just need simple functionality. Or you can use this as a starting point for your own implementation of the firmware.
These are new designs that haven't been fully tested yet. Use them at your own risk.
Andy Wardley abw@wardley.org December 2017