SPOKE is a Raspberry Pi RP2040-based capacitive touch sensor board for interactive computer interfaces. It is designed to simplify the integration of touch-based control into various projects.
SPOKE features up to 27 sensor inputs and can “turn almost any conductive material into a sensor” to control almost any computer input. Potential applications include music making, video game controlling, typing, and general software controlling.
The board was designed by Tom Fox, an educator, maker, and musician in the UK. According to him, the board is accessible to beginners getting started with touch sensing while retaining enough power and customizability for professional use. It works with several conductive materials, including copper pipes, conductive paint, aluminum foil, pencils, conductive filaments, fruits, fabrics with conductive threads, and metallic surfaces. It can also be used with a non-conductive material (such as plywood) if a conductive material (e.g. tinfoil) is behind it.
The fully-featured SPOKE capacitive touch sensor board uses the Raspberry Pi RP2040 microcontroller directly while the SPOKE-mini variant for embedded projects relies on the Raspberry Pi Pico microcontroller board.
The 25-key ESP32 touch matrix is a similar touch-sensing product created to serve a wireless keypad, and Dada Machines is another interesting product that uses MIDI triggers to turn everyday objects into musical instruments.
SPOKE specifications:
- MCU – Raspberry Pi RP2040, 32-bit dual-core Cortex-M0+ microcontroller @ 133MHz with 264KB SRAM
- Audio – USB-MIDI
- USB – USB-C connector (USB-MIDI, Keyboard or Mouse emulation)
- Expansion
- 27x touch sensor inputs (GP1 to GP25, GP28, and board.VOLTAGE_MONITOR)
- I2C connectors for extra I/O or daisy-chaining multiple boards
- Misc
- 27x NeoPixel 50×50 LEDs (GP00)
- Reset button
- Bootsel button
- Power Supply – 5V via USB-C
There is a working prototype of the SPOKE board but Tom says that “it will need changes before it is the best it can be.” These changes include new buttons, better graphics, and a modification of the USB-C controller. He also wants to develop an app and an instructional website to serve as a helpful resource and custom web MIDI player for building virtual instruments, samplers, and loopers.
The hardware runs CircuitPython and uses the native touchio library to handle capacitive touch sensing. The adafruit-midi library and adafruit-HID libraries are used for MIDI and keyboard+mouse emulation, respectively.
The maker provides a guide for building your own SPOKE board, and there is a GitHub repository with CircuitPython code samples.
The SPOKE touchboard controller campaign is crowdfunding on Kickstarter. Rewards include a shout-out in the example code for $13, the SPOKE-mini kit (including the board itself, the Raspberry Pi Pico, and 26 resistors) for $26, and the assembled SPOKE board for about $44. Optional add-ons include crocodile chips, copper tape, woven conductive tape, and a USB-A-to-C cable. Rewards are expected to ship by June 2025.
Tomisin is a writer specializing in hardware product reviews, comparisons, and explainers. He is very passionate about small form factor and single-board computers.
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