Bluetooth Low Energy (BLE)

Ariel OS supports BLE through TrouBLE. The hardware-specific initialization is handled by Ariel OS.

Enabling the BLE Stack

BLE is enabled by selecting one or both of the BLE laze modules depending on your use case:

• ble-peripheral: peripheral BLE role, allows for advertising the device’s presence.
• ble-central: central BLE role, allows for scanning and creating connections to devices.

If you want to learn more about BLE concepts, you can read the TrouBLE documentation.

Configuring the BLE Stack

The ability to configure which Bluetooth address is used and other capacity parameters like the MTU is planned in future updates.

Important

For compatibility reasons the MTU is fixed at 27 bytes.

The device address is randomly generated at boot and may be periodically rotated.

Current implementation: the address is a static device address and is not rotated during execution. This allows to use the BLE feature of Ariel OS on multiple devices in the same location. We later plan to switch to private device addresses by default, which are rotated during execution.

Using the BLE Stack

To use BLE in your application, you need to get the pre-configured stack and build the host instance from it:

#![allow(unused)]
fn main() {
let stack = ariel_os::ble::ble_stack().await;
let host = stack.build();
}

Here stack is of type trouble_host::Stack and host is of type trouble_host::Host.

You then need to run the runner background task in your application.

#![allow(unused)]
fn main() {
host.runner.run().await
}

Note

The runner has other options like run_with_handler(<handler>) that you may want to use (when scanning for example).

This function will return a result only when a critical error happened in the BLE stack. For most use cases you will need to execute code alongside the runner in the same task (that accesses elements of the stack or host), you can do that using embassy_futures::join::join:

#![allow(unused)]
fn main() {
embassy_futures::join::join(host.runner.run(), async {
  // Execute BLE-related code here that uses `host` or `stack`
}).await;
}

See the Ariel OS examples for more details.