Bluetooth & open source

BLE Bridge

BLE Bridge is an open-source adapter for software developers who need live data from Bluetooth Low Energy fitness equipment on a platform that has internet access, but no usable Bluetooth interface of its own.

Built for software that can reach the web, not the device

Game engines, hosted servers, simulations and restricted scripting environments often support ordinary HTTPS requests while exposing no Bluetooth stack. Adding a native driver may be impossible, operating-system-specific or simply far too heavy for the integration. BLE Bridge moves that hardware-specific work to a browser and gives the target software a small JSON API instead.

This keeps the consumer deliberately simple. It receives a connection code from the user, polls the relay for the latest measurements and works with familiar JSON objects. It does not need Web Bluetooth, a WebSocket client or physical proximity to the fitness device.

A mobile phone can become the Bluetooth edge

The browser bridge only needs to run near the sensor or trainer. That can be a laptop, but it can also be a compatible mobile phone with a Web Bluetooth-capable Chromium browser. The phone connects to the equipment locally, reads its GATT Services and forwards normalized telemetry through the internet. The game or dashboard can be running somewhere else entirely.

For a user, the workflow is lightweight: open BLE Bridge, choose the required GATT Services, connect the device in the browser's Bluetooth picker and copy the displayed connection code into the target application. No native bridge app has to be installed on the phone.

From GATT packets to ordinary JSON

1. The browser subscribes to supported GATT Characteristics and parses their binary measurements.
2. It sends normalized source data and the user's preferred measurement sources to the relay over WebSocket.
3. The in-memory relay keeps the latest snapshot available under the browser's connection code.
4. The target reads selected values or all available sources through standard HTTPS endpoints.

A demo endpoint can provide synthetic power data before any real equipment is available. This lets developers build and test the consumer side of an integration first, then replace the demo value with a real connection code later.

Several devices, one intentional source

BLE Bridge can connect to multiple devices at the same time. It understands common fitness standards including FTMS, Cycling Power, Cycling Speed and Cadence, Running Speed and Cadence, Heart Rate, Battery and Device Information. FTMS measurements cover indoor bikes, treadmills, rowers, cross trainers and climbing equipment.

Overlapping measurements remain separate. If a smart trainer and a pair of power pedals both report watts, the user can decide which source supplies the primary power value. Developers can use that curated view for a quick integration or inspect the complete source-first schema when device identity and protocol details matter.

Trainer control stays in the user's hands

Supported FTMS commands can travel back from the target application through the relay and browser to a smart trainer. Control is never silently enabled: the user selects the target device and grants the individual command types in the browser. Before writing, BLE Bridge checks the capabilities and value ranges advertised by the trainer.

Hosted for convenience, open for self-hosting

The public installation at blebridge.com is ready to use, while the complete MIT-licensed project is available on GitHub. A Docker setup packages the React frontend and Node.js relay together, and the repository documents both production hosting and direct development from source.

The relay deliberately has no workout database. It holds active channels and the latest telemetry in memory, then removes runtime state after the connection disappears or becomes idle. The physical Bluetooth link always remains between the user's browser and the device.