bt-broadcast-assistant

This crate implements the Broadcast Assistant role defined in the Bluetooth SIG Basic Audio Profile (BAP) v1.0.2 specification.

A Broadcast Assistant is a Bluetooth Low Energy (LE) device (typically a smartphone or tablet) that discovers Broadcast Sources and assists Broadcast Sinks (Scan Delegators) in synchronizing to LE Audio broadcast streams.

Overview

The bt-broadcast-assistant crate handles:

1. Broadcast Source Discovery & Synchronization:

   • Extended Advertising (EA) Scanning: Scans for advertisements containing the Broadcast Audio Announcement Service UUID (0x1852) to extract the Broadcast_ID and Broadcast_Name.
   • Periodic Advertising (PA) Synchronization: Automatically establishes Periodic Advertising sync using the platform's bt_gatt::periodic_advertising::PeriodicAdvertising trait when the Basic Audio Announcement Endpoint (BASE) structure (0x1851) is needed.
   • BASE Extraction: Parses subgroups, Codec IDs, Codec Specific Configurations, Metadata, and BIS indices from the PA train data.
   • Resource Management: Automatically cancels the PA sync once complete broadcast source information is gathered.

2. Scan Delegator Management:

   • Scans for peers advertising the Broadcast Audio Scan Service (BASS, 0x184F).
   • Establishes GATT connections to Scan Delegators and provides high-level control operations via bt_bass::BroadcastAudioScanServiceClient:
     • Add Broadcast Source
     • Modify Broadcast Source
     • Remove Broadcast Source
     • Set Broadcast Code

3. Platform Independence:

   • Uses the bt-gatt crate interface to remain Bluetooth stack- and async executor-agnostic.
   • On Fuchsia, integrated via bt-gatt-fuchsia (FuchsiaTypes).

Architecture

                  +--------------------------------+
                  |    BroadcastAssistant<T>       |
                  +--------------------------------+
                     /                          \
       +-----------------------+      +-----------------------+
       |   EventStream<T>      |      |   Peer<T>             |
       | (Source Discovery &   |      | (BASS Client for      |
       |  PA Sync via BASE)    |      |  Scan Delegator)      |
       +-----------------------+      +-----------------------+
                     \                          /
                  +--------------------------------+
                  |  T: bt_gatt::GattTypes         |
                  +--------------------------------+

Usage Example

# use futures::StreamExt;
# use bt_broadcast_assistant::assistant::Error;
use bt_broadcast_assistant::{event::Event, BroadcastAssistant};
use bt_gatt::central::Central;

async fn run_assistant<T: bt_gatt::GattTypes + 'static>(central: T::Central) -> Result<(), Error> {
    let mut assistant = BroadcastAssistant::<T>::new(central);
    // Start scanning for broadcast sources (EA + PA sync)
    let mut event_stream = assistant.start()?;
    while let Some(event_res) = event_stream.next().await {
        match event_res? {
            Event::FoundBroadcastSource { peer, advertising_sid, source } => {
                println!("Discovered complete broadcast source: {:?}", source);
                // Can now add this source to a connected scan delegator peer!
            }
            Event::CouldNotParseAdvertisingData { peer, error } => {
                eprintln!("Failed to parse advertisement from peer {:?}: {:?}", peer, error);
            }
        }
    }
    Ok(())
}