PHOTON

→ Read the paper · Hardware and firmware on GitHub

PHOTON measures how each key of a harpsichord, clavichord, or early fortepiano moves, and turns that motion into MIDI in real time, without interfering with the action. I designed and built all of it: schematic, PCB layout, firmware, and analysis.

Built to fit the instrument

• Any keyboard. Identical boards sit side by side under the keys, so one design covers any compass; a removable end segment handles odd key counts.
• Placed per instrument. A custom KiCad plugin places the sensors from each instrument’s measured guide-pin spacing.
• Less than 5 mm total board height. All surface-mount parts and low-profile connectors, to fit beneath the key levers.
• Mounting options. Various mounting options for harpsichords with a 13.33 mm jack and key pitch, including removable putty that needs no drilling.
• Calibrated per key. Each sensor records its rest and full-travel readings in place, so keys with different surfaces read alike.

Electronics

• An RP2350 on each board; the boards are daisy-chained over RS-485.
• USB-C in, stepped down to 3.3 V by a buck converter for efficiency. A full system runs from a laptop or even an iPhone.
• Shows up on a computer as USB MIDI, or as a higher-resolution position stream.

N. Jaffe and J. A. Burgoyne, “PHOTON: Non-Invasive Optical Tracking of Key-Lever Motion in Historical Keyboard Instruments,” NIME 2026. Paper · PDF