The Hat Knows Where It’s At

If I had a nickel for every time I saw a Bluetooth direction finding hardhat, I would be well on my way to purchasing a gumball. And that would all be thanks to a security researcher that goes by the handle S0lidStat3, who built one for fun and education. This hardhat, called Dendrite, may look strange, and it might be an extraordinarily odd platform to install a Bluetooth device locator on, but what it lacks in practicality, it more than makes up for in blinkenlights!

The basic premise is pretty simple — Dendrite has a ring of LEDs encircling it, and it scans all around itself to find broadcasting Bluetooth Low Energy (BLE) devices. If a device is found in a given direction, LEDs in that region of the ring are illuminated. S0lidStat3 built it to highlight the security risks associated with using BLE in emergency response applications, but it could just as easily be used to track down a lost dev board serving up an old website from somewhere in your house that you haven’t seen in years.

Dendrite draws power from a USB-C connection to drive a strip of WS2812B RGB LEDs. The lighting patterns are controlled by an ESP32-S3 microcontroller, which also coordinates the device’s overall operations. Four ESP32-C3 microcontrollers are used as Bluetooth scanners to locate any other devices that are nearby. These are positioned on the front, back, and left and right sides of the hat to provide directional information.

S0lidStat3 has made the circuit design and firmware publicly available, so feel free to hack away at it on your own. You could even build the system into a somewhat less awkward platform if you so choose.The full details are available on GitHub.