Embedded experiments

Various embedded experiments, including BLE Peripheral in Zephyr/C and Embassy/Rust, BLE Central (Rust), and async Rust.

Overview

• notifier (Zephyr, C): BLE Peripheral that advertises a 16‑bit service 0x183B with a single Notifiable characteristic (0x183C). It counts external events (button SW0 presses) and periodically notifies a 1‑byte value (sum of recent readings) every ~250 ms when a client subscribes.
• notifier (Embassy, Rust): BLE Peripheral that advertises a 16‑bit service 0x183B with a single Notifiable characteristic (0x183C). It counts external events (button SW0 presses) and periodically notifies a 1‑byte value (sum of recent readings) every ~250 ms when a client subscribes.
• subscriber (Rust): BLE Central that scans for the service, connects, subscribes to the first characteristic in the service, and collects three notifications (with a 10s timeout) using btleplug.

Service UUIDs (Bluetooth base UUID):

• Service: 0000183b-0000-1000-8000-00805f9b34fb
• Characteristic: 0000183c-0000-1000-8000-00805f9b34fb

Repo structure

• embedded-workspace/*: Zephyr applications (C, CMake)
• embassy-experiment/: Rust async embedded BLE peripheral for nRF52840 using Embassy and nrf-softdevice
• subscriber/: Rust workspace member (btleplug + tokio)
• pico-2w/: Minimal Rust embedded project for Raspberry Pi Pico W (rp235x-hal)

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Rust setup (one‑time)

Install Rust and toolchain:

curl https://sh.rustup.rs -sSf | sh

rustup default stable

Platform specifics for BLE (btleplug):

• macOS: Works with CoreBluetooth. Grant Bluetooth permission to your terminal/IDE in System Settings > Privacy & Security > Bluetooth.
• Linux: Install BlueZ; ensure your user can access BLE (may need bluetooth group and running bluetoothd).
• Windows: Uses Windows BLE APIs; run from a terminal with Bluetooth enabled.

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Embassy Rust Embedded Projects

embassy-experiment (nRF52840, async BLE peripheral)

• Uses Embassy async framework and nrf-softdevice for BLE
• Implements a custom GATT server and notification logic in async Rust
• Target: nRF52840 (see Cargo.toml for dependencies)

Build & flash:

cd embassy-experiment
# Set up your toolchain for thumbv7em-none-eabi (see Embassy docs)
cargo build --release
# Use your preferred flashing tool (e.g., probe-rs, nrfjprog)
probe-rs download target/thumbv7em-none-eabihf/release/embassy-experiment --chip nRF52840_xxAA

pico-2w (Raspberry Pi Pico W)

• Minimal Rust project using rp235x-hal and defmt logging
• Example for getting started with embedded Rust on the Pico W

Build:

cd pico-2w
cargo build --release --target thumbv8m.main-none-eabihf
# Flash with your preferred tool

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Zephyr setup (one‑time)

1. Install toolchain and West, reference the official guide (recommended): https://docs.zephyrproject.org/latest/develop/getting_started/index.html

cd embedded-workspace
python -m venv .venv
source .venv/bin/activate

pip install west

west init
west update

west zephyr-export
west packages pip --install

cd zephyr

west sdk install -t arm-zephyr-eabi

Build and flash the notifier (Zephyr)

This repo (ble-experiments) contains a workspace app. You will build each embedded app from its own project directory.

From your project directory (e.g., embedded-workspace):

# Example for Nordic nRF52840 DK; change -b to your board (e.g., nrf52dk_nrf52832)
west build -p always -b nrf52840dk/nrf52840 
west flash --runner jlink

RTT logging (optional):

west debugserver
west rtt

Notes

• The app enables RTT and disables UART console (prj.conf). If your board lacks J‑Link/RTT, switch console to UART in prj.conf.
• The app uses DT alias sw0 as the button input; ensure your board defines it (most Zephyr reference boards do).

Run the Rust subscriber

From the repo root:

cargo run -p subscriber

What it does

• Selects the first BLE adapter
• Scans for service 0000183b‑0000‑1000‑8000‑00805f9b34fb
• Connects, discovers services, subscribes to the first characteristic in that service
• Collects 3 notifications (times out after 10 s)

Expected behavior

• Press the board’s user button (SW0) a few times; the peripheral accumulates a 1‑byte sum and notifies periodically when subscribed.
• The subscriber logs three 1‑byte values and exits.

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End‑to‑end quick start

1. Flash the Zephyr notifier to your board and power it on.
2. Start RTT (optional) to see logs from the board.
3. Run cargo run -p subscriber on your desktop.
4. You should see a connection and three notifications within 10 seconds.

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Configuration reference

• Advertising name: CONFIG_BT_DEVICE_NAME in notifier/prj.conf (default: "Notifier 1")
• Advertising flags: General Discoverable, no BR/EDR
• Peripheral role, GATT dynamic DB, extended advertising enabled
• Notify period: ~250 ms (see my_thread_entry_point in notifier/src/main.c)
• Button: DT alias sw0 (notifier/src/external_readings.c)
• Storage: simple heap‑backed list with a cap of 25 readings (storage.c/.h)

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Troubleshooting

• Subscriber can’t find adapters
  • Ensure Bluetooth is enabled; on macOS grant Bluetooth permission to your terminal/IDE; on Linux ensure BlueZ is running.
• No notifications
  • Ensure the client has subscribed; verify the service/characteristic UUIDs match; press SW0 to generate readings.
• Zephyr - no console output from the board
  • Use RTT (requires J‑Link) or switch to UART console by updating prj.conf.

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License

MIT

Notes

This README was written and updated with the help of AI.