tobiifree - ET5 on Linux & Web

An ongoing experiment to make Tobii eye trackers work on Linux.

The Tobii Eye Tracker 5 (ET5) ships with Windows-only drivers and no public protocol documentation. Under EU law — specifically the European Interoperability Act and related directives — reverse engineering for interoperability purposes is permitted. This project exercises that right to bring eye tracking to Linux users.

Status: experimental. The USB wire protocol was decoded by observing the device's standard USB bulk transfers. Things work, things break, things change.

Demo: https://aetherall.github.io/tobiifree/

What's here

• driver/ — Zig implementation of the TTP/TLV framing protocol. Compiles to both WebAssembly (for the browser SDK) and native (for the Linux applications). Pure byte-level protocol engine — no allocator, no syscalls.
• sdk/ — TypeScript SDK wrapping the wasm core. Works in the browser (WebUSB) and Node.js (usb package). Tobii.fromUsb() to connect, subscribeToGaze() to stream.
• applications/tobiifreed — Linux daemon. Talks to the tracker over libusb, exposes gaze data over a Unix socket (and optionally WebSocket).
• applications/tobiifree-overlay — GTK4 + layer-shell overlay that draws a gaze dot on your Wayland desktop. Connects directly via USB or through the daemon.
• applications/tobiifree-demo — Browser app for live gaze visualization, calibration, and display area configuration. Hosted on GitHub Pages.
• assets/ — Firmware tools (DFU flash/extract) and udev rules.

Quick start

Prerequisites

Nix with flakes enabled, or Zig 0.14+ and Node.js 22+ installed manually.

# Enter the dev shell (provides zig, node, libusb, gtk4, etc.)
nix develop

# USB permissions (run once)
sudo cp assets/99-tobii.rules /etc/udev/rules.d/
sudo udevadm control --reload && sudo udevadm trigger

Build and run

# Run the daemon (direct USB)
just tobiifreed

# Run the gaze overlay (direct USB)
just overlay

# Run the overlay through the daemon (Unix socket)
just tobiifreed                # terminal 1
just overlay -- --socket   # terminal 2

# Run the browser demo (WebUSB, opens http://localhost:5173)
just bundle   # build wasm + embed in SDK
just demo

Nix packages

nix build .#tobiifreed        # daemon binary
nix build .#tobiifree-overlay # GTK4 overlay binary
nix build .#tobiifree-demo     # static SPA (deployable to any web server)

Supported hardware

Device	VID:PID	Status
Tobii Eye Tracker 5 (runtime)	2104:0313	Working — gaze, calibration, display area
Tobii Eye Tracker 5 (bootloader)	2104:0102	DFU flash only

License

GPL-3.0