I have an idea to build a MIDI pedal board for sending MIDI messages to a laptop while I'm playing guitar. It could send note messages (to trigger samples), or program changes (to change effects) or many other combinations.
Videos like this by Hacker Shack and this by Notes and Volts make it look easy - well, at least not crazy difficult. And parts are both easy to obtain and cheap.
Specialised parts, like this sloped aluminuim enclosure, could give the unit a real professional finish. And by adding a TFT touchscreen I could build something really powerful - and completely bespoke to me.
Easy, right?
The first prototype I have built is housed in a plastic box (the kind with compartments used to store screws). This box was £6.99, a whole lot cheaper than buying a proper aluminium enclosure. By luck the compartments are pretty much exactly the right spacing for the buttons.
The parts I got were:
- Teensy 4.1, the brains of the unit
- Soft-touch footswitches (the clicking ones would be loud and annoying)
- Breadboard, jumper wires, and LEDs from pimoroni.com
- 2.8 ince ILI9341 TFT touchscreen
- COmpartment organiser box
The code was written in C++ using the excellent Arduino IDE, with libraries and help from pjrc.com.
There are currently two 'sketches' (the name for Arduino scripts):
- MTP: a sketch to make the Teensy act as a mass storage device so the JSON config file can be copied to it
- ChordPlayer: makes the unit send chords (multiple MIDI notes at once) as accompianment. I plan to use this with synth pad sounds while I'm playing guitar.
This initial prototype has a few features, mostly built to try out how all this stuff works!
- 5 of the buttons send chords, which can be defined in the config file for each key
- Ability to change key (clockwise or anti-clockwise) round the cycle of fifths)
- 4 "registers" per key. A register is where the chords are on the keyboard - low, middle, high or wide (i.e. a chord spread across 3/4 octaves)
- Ability to change MIDI channel so I can change patches
I hope to have a video demonstration available soon.
Before I started physically building anything I made a pure software prototype. In the html-prototype folder you'll find several files related to this prototype written in HTML, CSS and JavaScript. I know these technologies pretty well, so felt I could make a lot of progress quickly.
13-buttons.html was the initial idea for this unit, with 13 buttons. However, I printed out the design on paper at scale and the buttons were too close together to be usable by my big feet!
drawing.svg and drawing.pdf are the diagram I created to print out on paper (A4 paper is 297mm long, and the unit is 300mm long, which is close enough for jazz)
7-buttons.html was my next design, with 7 buttons. This is definitely more comfortable to play - and meant I could put the screen in landscape mode.
index.html is the next version, still with 7 buttons but using a JSON configuration file to define the modes and actions of each button (or set of buttons) for each mode.
config-example.json is the example config file, in JSON format. This config would define what the buttons do - making the unit a platform which could do pretty much anything the user wanted it to. While a nerd like me could edit configs like this by hand, if anyone else were to use this a GUI to edit the file would be necessary. I imagine something like the Blackstar Live Logic app:
