Writing Embedded Rust Code to Connect Microbit Bluetooth Low Energy (BLE) with a Phone

We have seen what a BLE stack is and understood the basic concepts. Now it's time to use that knowledge in action. We will write a simple (narrator: the author was lying) project that lets the micro:bit send and receive data from a phone.

Our program will include one BLE service called BatteryService. A connected device (like your phone) can either read the current battery level or subscribe to get updates whenever the battery level changes.

Create Project from template

We will use Embassy again, but this time without the BSP. Instead, we will work directly with the embassy-nrf HAL.

cargo generate --git https://github.com/ImplFerris/mb2-template.git --rev 3d07b56

• When it prompts for a project name, type something like "hell-ble".

• When it prompts whether to use async, select "true".

• When it prompts you to select between "BSP" or "HAL", select the option "HAL".

Project Structure

This exercise is adapted from the ble_bas_peripheral_notify.rs example in the nrf-softdevice repository, with some restructuring for clarity. You can explore more examples here.

Below is the structure of the src folder we will build. We'll create a ble module to hold common Bluetooth-related setup and configuration, and a separate service.rs file for the battery service logic.

.
├── ble
│   ├── adv.rs
│   ├── config.rs
│   └── mod.rs
├── main.rs
└── service.rs

1 directory, 5 files