BLE Angle Guide

This project is my attempt to create a BLE knife sharpening angle guide/sensor that magnetically clips onto the side of your knife. The UI is a webpage which talks to the sensor using WebBluetooth. The hardware is a custom PCB based around a Panasonic nRF52840 module. The firmware is implemented in Rust using Embassy. It's my first foray into embedded systems, so the PCB design is probably terrible.

Project Structure

• hardware/: KiCad files for the PCB
• firmware/: Rust firmware for the nRF52840 module
• ui/: Web-based UI (just an index.html file)

Building the Firmware

The board has 1.27mm/0.05" pitch 2x5 pads which can be connected to using something like https://www.adafruit.com/product/5434. For anyone wanting to develop something similar, a 10 pin connector is unnecessary; all you need is 4 pins: SWCLK, SWDIO, GND, and VCC.

To build and debug, run cargo run --release from the firmware directory. Note: the CPU seems to hardfault after some time if running without the --release flag. I haven't figured out why yet; I'm guessing it has to do with a stack overflow.

To flash the device, run sh flash.sh from the firmware directory.

UI

The UI is just a single index.html file. WebBluetooth requires an https connection, so development-server.py is included for running a simple HTTP server with TLS support. It requires that mkcert be installed or that you manually generate cert.pem and key.pem.

Known Issues

• On/off button logic hasn't been implemented yet in the firmware
• USB connector is currently unused in firmware