Pitmaster BLE Terminal

I recently bought a Bfour BF-30 as a budget BLE thermometer and it works great for slow cooking meat. But its Android app is a nightmare: trying to get your attention with all sort of different ways with apparently no way of turning it off and one feature I was deeply missing was some kind of trend in temperature to know how much time to expect until it hits temperature or if the temperature delta is slowing and I need to add extra coal or open the vents on my grill.

While waiting on the BBQ, I used opencode with DeepSeek-V4 to build a browser-based replacement. It turned out to be much more straight forward than I originally thought.

The probe sends an RF signal to the base station, which broadcasts to mobile devices over Bluetooth LE. Using the Web Bluetooth API, a browser reads the exact data stream sent to the native app.

Rather than guessing payload structures, the coding agent identified that the BF-30 uses a generic "Grill 5.0" BLE module already documented in home automation projects like Home Assistant. Using those known GATT characteristics, the agent subscribed to the notification stream and decoded the incoming bytes within the very first minutes of trying to get it working.

The payload structure contains six 16-bit integers, accommodating up to six probes on higher-end models using the same firmware. The device records temperatures as scaled integers, so a reading of 20.1C is transfered on the wire as 201 (0x00C9).

Within minutes, I had a working prototype with temperature being reported in realtime and notifications. I then moved from basic telemetry and added a forecast alert driven by three exponential moving average windows to track short, medium, and long-term temperature trends.

I really believe i'm not the only one doing this kind of tinkering with everything tech that bother them and was surprised by the serendipity of seeing this post right around the same time I was working on this.

This pattern mirrors my experience in corporate banking and why I think coding agents are the new Excel: when central IT build rigid tools, every department built custom workarounds using Excel formulas and VBScript to glue all the custom behavior together. Coding agents are playing that exact same role today, you're always one prompt away of trying your shot at reversing protocol specs and building a custom single-purpose tool for your specific needs in minutes.

You can check out the interactive project here: Pitmaster BLE Terminal.