We asked our 2024-25 Accessible Instrument Development Fund grantees to document their journey towards creating a brand new accessible instrument. One of our grantees, Tom Fox, wrote the below blog to provide a detailed insight into how their instrument, Tim’s Palm, was made!
Tim’s Palm, by Tom Fox
My name’s Tom Fox, I’m a creative technologist who’s spent over a decade working with musical instrument design, running workshops, networking events and hackathons through Hackoustic in London and MusicTechFest Labs throughout Europe. It was at one of these MTF events in Stockholm, Sweden, back in 2018, that I first met Tim Palm – a musician and DJ whose condition leaves him with limited range of movement. Tim typically controls his setup using his nose or tongue, demonstrating the kind of creative adaptation that constantly inspires me in this community.
Over the years since that first meeting, Tim and I have collaborated on a few projects together based around education in some Erasmus pilot projects.
The Technical Discovery
More recently, over the past couple of years, I started exploring capacitive touch-based instruments, trying to find the most cost-effective solution possible. That’s when I stumbled upon something remarkable: the Raspberry Pi Pico can perform capacitive touch sensing by simply adding a 1MΩ resistor to any GPIO pin.
After some testing, I discovered you could use ALL 26 GPIO pins on the Pico to create 26 individual touch sensors – for an incredibly reasonable cost. Having worked with Bare Conductive and MaKeyMaKey in workshops, I knew the educational and accessibility potential was enormous.
This discovery led me to design some PCBs and launch a Kickstarter campaign for SPOKE – an open-source capacitive touch platform to make this ultra-affordable hardware available to other makers and educators. All the code is freely available on the project’s GitHub for anyone looking for super simple capacitive touch USB-MIDI projects. But I also saw an opportunity to create something more personal.
When the chance came to focus on a dedicated project, I knew I wanted to build something specifically for Tim. The goal was to give him more control options while creating a template that could help other artists customize touch-sensing hardware for their needs.
There was one major challenge: Tim lives in Sweden, I’m in the UK, and my full-time teaching job meant popping over for measurements wasn’t exactly feasible.
One of the biggest early hurdles was figuring out Tim’s exact range of motion and getting those measurements to me so I could build the instrument to the right scale. The solution was brilliantly simple: finger paints!
I had Tim dip his finger in paint, make marks on paper, then photograph the results next to a ruler. This surprisingly low-tech approach gave me everything I needed – not just the measurements of his finger pads, but the distances between separate sensors and even the actual shape of his finger.
Using this data, I designed each touch sensor pad around the shape of one of Tim’s fingermarks, spacing them out according to the distances shown in his paint patterns. It’s probably one of the most personal approaches to instrument design I’ve ever used.
Engineering the Hardware
With my background in PCB design, translating the concept into reality using KiCAD was straightforward – though Tim did make things interesting by requesting both a flat section and a secondary part at a 90-degree angle. This meant designing two interconnected PCBs controlled by a single microcontroller.
Final 3D layout of sensors and toggle buttons.
Each touch sensor needed a NeoPixel LED as a visual indicator, which I chose specifically because it’s easy to map LEDs in their chain to whatever sensor they’re positioned next to. The whole system runs on CircuitPython with the touchio library handling the capacitive sensing and outputs USB-MIDI and CC control messages for seamless integration with music software.
On the bottom row were triggers for note on- note off midi notes, while the top row would be able to toggle on/off for sustained notes. The far left and right sensors would be able to toggle the notes played through a series of banks of notes, so that different scales or octaves could be played.
Knowing that troubleshooting from hundreds of miles away would be inevitable, I designed maximum flexibility into both the hardware and software. If issues arose, they could likely be fixed through code updates that I could test on my spare unit at home, with Tim simply copying and pasting new code on his end.
One of the beautiful things about CircuitPython is its accessibility – you don’t need specialized software to edit the code. Tim can make adjustments using something as simple as Notepad. This democratization of customization was exactly what the project needed.
As I write this, Tim has received his prototype and is putting it through its paces. There are some LED issues that appear to be shipping damage – a reminder that even the most careful planning can’t account for postal services! I’ll be sending out a replacement unit after my upcoming talk to Drake on the 28th.
Beyond the Individual: A Template for Inclusion
While Tim’s Palm was built for one person, the process revealed something larger. The combination of ultra-affordable hardware (thanks to the Pico’s capabilities), remote collaboration techniques (hello, finger paints!), and flexible software created a replicable framework for custom accessibility instruments.
The project demonstrates that meaningful assistive technology doesn’t require massive budgets or in-person collaboration. Sometimes it just needs creative problem-solving, appropriate technology choices, and a willingness to think outside conventional design processes.
Technical Specifications
Hardware Foundation:
- Raspberry Pi Pico microcontroller
- Custom dual-PCB design (flat + 90-degree sections)
- 20 touch sensors using 1MΩ resistors
- NeoPixel LED indicators for each sensor
- Designed around user-specific finger measurements
Software Stack:
- CircuitPython firmware
- touchio library for capacitive sensing
- USB-MIDI and CC control output
- User-customizable code via simple text editing
- HID device capability for keyboard/mouse inputs
Beyond Music: Broader Applications
While Tim’s Palm was designed as a musical controller outputting USB-MIDI and CC messages, the Raspberry Pi Pico’s HID device capabilities open up much broader possibilities. The same hardware and techniques could easily be customized to:
- Control software applications through keyboard shortcuts
- Provide mouse input alternatives
- Create custom accessibility interfaces for computer navigation
- Build specialized control surfaces for creative software beyond music
This flexibility makes the approach valuable not just for musicians, but for anyone needing customized touch-based computer interaction.
The Broader Impact
This project sits at the intersection of several movements I care deeply about: accessible design, maker culture, and the democratization of technology. By documenting the process – from paint-based measurements to PCB design – I hope other makers can adapt these techniques for their own accessibility projects, whether musical or otherwise.
The MusicTechFest and Hackoustic communities have always emphasized that the best technology serves real human needs. Tim’s Palm embodies this philosophy, proving that sometimes the most sophisticated solution is built from the simplest techniques.
Looking Forward
Tim’s feedback on the prototype will undoubtedly lead to improvements and iterations. But beyond this specific instrument, I’m excited about the broader possibilities. The techniques developed here – remote measurement capture, ultra-affordable touch sensing, flexible software architecture – could be applied to countless other accessibility challenges.
Every musician deserves tools that amplify their creativity rather than limit it. Projects like Tim’s Palm remind us that with thoughtful design and collaborative spirit, we can build technology that truly serves everyone.
The Tim’s Palm project represents the kind of human-centered innovation that emerges from maker communities worldwide. The underlying SPOKE platform and all associated code are open-source and available on GitHub. If you’re working on similar accessibility projects or want to explore capacitive touch sensing for music, software control, or computer interaction, the techniques and discoveries documented here are yours to build upon.
You can also watch Tom present his work at our DMLab London event in July:
Thanks to Tom for documenting his work with Tim’s Palm!
Discover more of Tom’s work
Tom’s portfolio
Tom’s Instagram
SPOKE Instagram
Our Accessible Instrument Development Fund, a part of DMLab London, is supported by the City of London Corporation’s charitable funder, City Bridge Trust, London Catalyst, and with public funding from Arts Council England.
