One knob. A light bar that previews each setting.

A personal hardware build with smooth LED motion, live settings and current-aware rendering on a Feather M4.

Marcus Rydberg · Independent build with coding agentsC++ · Feather M4 · I²C

Curved LED light bar on a desk with a controller board and rotary encoder — The physical prototype on the bench, mid-sweep. Click image to enlarge.

Why I built it

I wanted a light bar whose settings could be adjusted and previewed directly on the device. A small display and rotary encoder became the entire setup interface.

Engineering decisions

Render fractional LED positions with anti-aliasing in a fixed-timestep loop.

Estimate current every frame and dim output when it exceeds the configured supply budget.

Share one parameter table between the menu and rendering engine, with debounced persistence to flash.

What works today

A working personal prototype using a Feather M4 and 144-LED strip. The C++ firmware replaced an earlier CircuitPython version in June 2026.

Current boundaries

A hardware and interaction-design project in personal use. It is not presented as a validated clinical product.

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