How to Make a Wearable MIDI Control System

Goal: Build a musical instrument that converts any body movement into any sound, enabling the user to generate electronic music by dancing

Prior Work: Built a working prototype using development boards, but knew essentially nothing about micocontrollers, 3D design, or fabrication equipment

Note: This page summarizes the journey leading up to the final demo video above. For detailed instruction, see the sub-project pages linked throughout.

Components:

Wearable Electronic Device

Measures body movement
Transmits data wirelessly
Is modular, enabling rapid prototyping

Wireless Receiver

Receives data from the wearable device
Converts the data into MIDI signals
Transmits the MIDI signals to a computer via USB

Laptop Mount for a Wearable Speaker

Securely fastens to the speaker and laptop
Allows access to speaker controls and laptop ports
Affords the wearer complete mobility

Sources:

Circuit Boards: Custom (milled or printed)
Laptop Mount: Custom (particle board using CNC)
3D Models: Custom (CAD using Fusion 360)
Software: Custom (C++/Python)
Electronics Cases: Custom (3D prints)
Sensor: IMU BNO-086 by CEVA/Bosch
Microcontroller: Xiao ESP32-S3 by SEEED/Espressif
Wearable Speaker: Soundboks Go
Laptop: MacBook Air M2

Process:

Each week of the class we learn a new skill and have a corresponding assingment
When possible, I aligned those assignment with the final project's devlopment
Here, I review the process leading up to the final demo shown above, referencing weekly projects along the way
It started with a sketch...

And, a corresponding 3D model (Week 1: Computer-Aided Design)

An artist's rendering of the what I imagined the final electronics to be
Shortly thereafter, I learned about the SEEED XIAO microcontroller series, which is very close to the form factor I imagined
I started experimenting with them, first as a USB MIDI controller (Week 3: Embedded Programming)

Then, around my original 3D electronics model, I designed and printed a snap-fit case (Week 4: 3D Printing)

Note: Turn the audio on to hear that excellent snap fit
Then, it came time to start designing actual electronics
Questions arose, like:

What sensor will I use?
How will the microcontroller connect to it?
Would I like to connect other devices? Maybe a screen?
What about other inputs? Buttons? Knobs? Switches?

At this point, I realized...
- I don't know what features this wearable needs in its final form
- And, I won't know until I'm using it
So, I designed a board with modularity in mind:

Convert all of the pins into headers that easily be connected to
Ensure power and ground are easily accessible
Conveniently arrange pins commonly used together
For instance, the 4 pins required for I2C communication protocol

I designed a first electronics draft (Week 5: Electronics Design)
And then, produced it (Week 6: Electronics Production)

The first one didn't work due mistakes in assembly
But, ultimately this board design proved to be very useful
Here, it can be seen reading sensor data for the first time (Week 9: Input Devices)

And, here it is sending that data to an onboard screen (Week 10: Output Devices)

And, here it is sending that data wirelessly (Week 11: Networking and Communications)

And, here it is sending that data to a computer (Week 12: Interface and Application Programming)

Pretty cool, huh?
At this point, I had a working prototype, but was still dependendent on a development board for the IMU (the thing with a green LED in the videos above)
I wanted to design my own IMU circuit board that contained the minimal circuitry necessary for an I2C connection
This will allow more control over form factor, enabling me to get closer to the original design I imagined
This presents several challenges:

PCB design: must design circuit as recommended by Bosch example schematics (not as simple as connecting the 4x I2C pins like before)
PCB manufacturing: must order this PCB from a manufactuer
PCB assembly: must solder very tiny components to the PCB

How tiny?

On the left: the IMU development board in all the videos above
On the right: the IMU from that board that I have to design a circuit around and somehow solder
See that week's page for the full details on this, but behold! A working custom IMU PCB! (Week 14: Input Devices (Custom PCB))

Now, that's an accomplishment, but is it an improvement?
Not really... Not yet. But that's just the first draft
Empowered by this, I designed one last PCB to be manufactured
The goal was to compress all the components in the videos above into... this:

Isn't it beautiful? A compact form-factor that preserves all of the functionality of the original
With the board, I planned to design a case to match with slots that allow access to the headers
This would allow me to design input (e.g. buttons/knobs) and output (e.g. oled screen) modules then plug them in to test
All in a sleek package
If it had worked...
It almost worked...

The lights are on, but nobody's home
Systematically, board after board, a power-related failure
Even though the schematic for this board is essentially the same as the one that worked
There's something incorrect that is to-be-determined
Out of time, I proceeded to the final demo with the original prototype
But, I'm not done with this project yet

More chips to come some day!
But wait... One last thing before we wrap this up
The laptop mount (Week 8: Computer-Controlled Machining)
Making the laptop mount proved more challenging than expected. I had to...
- Make an exact 3D model of the speaker and laptop
- Slice the 3D mount into pieces the same thickness as the wood
- Then cut, assemble, and sand (alot... alot of sanding) the wood
Behold! A perfectly snug laptop mount

And, a very comfortable mobile setup

Alright, that's all folks!
Thanks for checking it out

Notes:

Please feel free to get in touch if you'd like to chat -- you can find my latest contact info online somewhere
Attached below are all the relevant files for the final demonstration
For sub-project files, see respective pages

Files:

3D Models:

Electronics:

Milled PCB Traces
Milled PCB Outline
BNO-086 I2C PCB Schematic (v1: functional)
BNO-086 I2C PCB Board (v1: functional)
BNO-086 I2C PCB Schematic (v2: non-functional)
BNO-086 I2C PCB Board (v2: non-functional)

Software:

Wearable Sensor and Wireless Transmitter (.ino)
USB-MIDI Device and Wireless Receiver (.ino)