Keybytes modular keyboard uses per-key RISC-V microcontrollers, open-sourced under MIT

MIT student Nathan Alspaugh (notaroomba) has released Keybytes, a fully modular mechanical keyboard project where every individual key is a self-contained unit with its own RISC-V microcontroller. The system centers on a 'Keyword' hub board with an Arm Cortex-M4, Bluetooth, and USB-C, to which users magnetically attach 'Keybit' modules measuring 19.05 x 19.05mm each. Every Keybit uses a CH32V003 RISC-V MCU and exposes pogo pins on all four sides for power and I2C communication, enabling keys to snap together in any configuration without a fixed PCB matrix.

The entire project is open-sourced on GitHub under the MIT license, including PCB designs, firmware, and mechanical files. Alspaugh estimates a full-size 110-key build with two Keywords would cost approximately $900 in components. The project reached a working state in October 2026 after beginning in March 2026, though current Keybits lack per-key RGB lighting and the GitHub repository only demonstrates two Keybits connected so far.

Architecture and microcontroller design

• Keyword hub: Stacked dual-PCB design with an Arm Cortex-M4 microcontroller, Bluetooth antenna, flash memory on the top board; USB-C port, charging circuitry, and buck-boost converter on the lower board.
• Per-key compute: Each Keybit module runs a WCH CH32V003 RISC-V microcontroller, a low-cost 32-bit RV32EC core with embedded flash, handling individual key scanning and I2C communication independently.
• Magnetic interconnect: Pogo pins on all four sides of every 1U Keybit provide power distribution and I2C bus connectivity; magnetic cases allow mechanical attachment to the Keyword hub or adjacent Keybits in any orientation.
• Switch compatibility: Keybits accept standard Cherry MX mechanical switches; users can substitute preferred switch types following the MIT-licensed design files.
• Form factor: Both Keyword and Keybit modules conform to standard 1U keycap spacing at 19.05 x 19.05mm, preserving compatibility with existing keycap sets.

Why it matters

Keybytes represents a rare fully open-hardware input device architecture that pushes per-key intelligence to inexpensive RISC-V microcontrollers rather than centralized matrix scanning. For the open-hardware community, the MIT-licensed release of PCB files, firmware, and mechanical designs provides a reference platform for rethinking human interface devices as composable, network-attached peripherals rather than fixed-layout PCBs. The project's use of commodity CH32V003 MCUs and standard Cherry MX switches lowers barriers for derivative works, though the $900 estimated cost for a full-size build and the soldering requirements will likely limit adoption to dedicated hobbyists and researchers exploring modular input paradigms.