Etherbulb open firmware turns ESP32-C3 smart bulb into RF spectrum visualizer
Etherbulb is GPL-3.0-or-later firmware that repurposes an ESP32-C3 smart bulb as a receive-only 2.4 GHz RF monitor, displaying signal types through color-coded light output with no cloud dependency.
Summary
Peter Holzhauser released Etherbulb on GitHub, open-source firmware for ESP32-C3 smart bulbs that visualizes nearby radio frequency activity. The bulb glows blue for Bluetooth, green for Wi-Fi, and a user-selected color for other signals, with brightness indicating signal strength. It requires no app, cloud service, or account, and does not decode content or transmit. The firmware includes a local JSON API and web dashboard for status, configuration, logs, and raw spectrum snapshots.
How Etherbulb works
- Hardware target: Inexpensive ESP32-C3 based smart bulbs
- RF coverage: 2.4 GHz band plus adjacent mobile bands, receive-only
- Signal classification: Bluetooth (blue), Wi-Fi (green), user-configurable color for other signal types
- Brightness mapping: Stronger signals produce brighter light output
- Safety mechanism: Hardware-enforced PWM duty cycle check prevents simultaneous RGB and white channel operation
- Receiver path: Derived from ESPARGOS project's esp-sdr by Florian Euchner, Zoltan Doczi and contributors
- Band tables: Sourced from ESPsoup app
- Build requirements: Specific ESP-IDF commit, Python 3.12
- Local interfaces: Self-hosted JSON API and dashboard with endpoints for status, configuration, log, and raw RF snapshot
Why it matters
Etherbulb demonstrates a practical open-hardware approach to RF awareness using commodity IoT hardware, eliminating cloud dependencies typical of consumer smart bulbs. Its reuse of ESPARGOS and ESPsoup components shows growing tooling maturity for ESP32-based software-defined radio applications.
Original reference: blog.adafruit.com →