An RP2040-based LED fire simulation controller that drives WS2812B NeoPixel strings to recreate the look of a glowing fireplace.
Full writeup: davidcapper.dev/posts/fire-string
Finished units available at hortus.dev/products/fire-string.
The simulation is built on three physical concepts:
- Black-body radiation — pixel temperatures are mapped to a colour gradient from red (cool) through orange/yellow to white (hot).
- Heat decay — each pixel loses a proportion of its heat every frame, fading from bright to dark over time.
- Thermal diffusion — pixels transfer heat to neighbours proportionally to temperature difference, so heat spreads naturally through the string.
On top of this, a fuel system adds gradual brightness ramps (fuel converts to heat via a burn rate), and temperature-dependent curves make cool pixels decay slowly and reignite easily while hot pixels shed heat rapidly — mimicking real ember behaviour.
CircuitPython running on the RP2040 with @micropython.viper compilation and integer-only maths for performance. Includes a web-based configurator (Web Serial API) for real-time parameter tuning and preset management.
Custom 2-layer RP2040 PCB with USB-C, designed in KiCad. Schematic and board layout are in hardware/.
- Hardware — CC BY-NC-SA 4.0
- Software — MIT
