This example acts as a BAP Broadcast Source. It creates a BAP broadcast source from the LC3 16_2_1 broadcast preset, encodes the BASE into the periodic advertising payload, places the Broadcast Audio Announcement Service UUID and a fixed 24-bit Broadcast ID (0x123456) in the extended advertising payload, and then starts the BIG so that BIS streams transmit synthetic SDU data on a fixed cadence.

The build runs on top of the selected BLE host stack (Bluedroid by default; NimBLE via the sdkconfig.defaults.nimble overlay) and the ESP BLE Audio component set. Source-side APIs used: esp_ble_audio_common_init / esp_ble_audio_common_start (common layer), esp_ble_audio_bap_broadcast_source_create / _get_base / _start (BAP), esp_ble_audio_bap_broadcast_adv_add (BAP/ISO glue), and the BAP stream callbacks (started, stopped, sent, disconnected). PACS, GAP scanner, and the scan delegator are not used on this side. Encryption is enabled because the broadcast code "1234" is non-empty; packing is ESP_BLE_ISO_PACKING_SEQUENTIAL. Channel allocation per stream is hard-coded as FRONT_LEFT for stream 0 and FRONT_RIGHT for stream 1.

The TX scheduler is built on example_audio_tx_scheduler_* helpers; the source comment notes that ESP timer resolution is not accurate enough for the SDU interval, so a k_work_delayable-based scheduler is used instead.

Requirements

A board with Bluetooth LE 5.2, ISO, and LE Audio support (e.g. ESP32-H4, ESP32-S31)
A peer running the broadcast_sink example to receive and decode the BIS streams

Configuration

Open menuconfig:

idf.py menuconfig

No build-time options — runtime defaults are baked into source. The device name ("BAP Broadcast Source"), broadcast ID (0x123456), broadcast code ("1234"), advertising/periodic intervals, stream and subgroup counts (via CONFIG_BT_BAP_BROADCAST_SRC_STREAM_COUNT / _SUBGROUP_COUNT from the BAP component), and LC3 preset (16_2_1) are compile-time constants in main.c.

Security & Pairing

The example inherits a Just-Works pairing model (LE Secure Connections, no MITM, no I/O capability) with bonding enabled from the shared init at ../common_components/example_init/ble_audio_example_init.c; change pairing/IO-cap there if needed.

Build & Flash

The base sdkconfig.defaults defaults to the Bluedroid host; idf.py automatically merges the per-target overlay (sdkconfig.defaults.$IDF_TARGET). To build with NimBLE host instead, layer sdkconfig.defaults.nimble on top via -DSDKCONFIG_DEFAULTS.

Bluedroid host (default)

idf.py set-target esp32h4
idf.py -p PORT flash monitor

NimBLE host

idf.py set-target esp32h4
idf.py -DSDKCONFIG_DEFAULTS="sdkconfig.defaults;sdkconfig.defaults.esp32h4;sdkconfig.defaults.nimble" -p PORT flash monitor

For esp32s31, replace the chip overlay accordingly.

(Exit serial monitor with Ctrl-].)

Example Flow

app_main initializes NVS, calls bluetooth_init(), and calls esp_ble_audio_common_init(NULL) (no GAP callback for this role).
broadcast_source_setup() registers source_started / source_stopped callbacks, populates per-stream channel-allocation BIS metadata (left/right), registers stream_ops on each stream, and calls esp_ble_audio_bap_broadcast_source_create() with the encrypted preset.
esp_ble_audio_common_start(NULL) starts the audio stack; each stream's example_audio_tx_scheduler_init() is wired with tx_scheduler_cb.
adv_init() performs host-specific GAP setup (Bluedroid: registers the GAP callback for *_COMPLETE_EVT semaphore signalling; NimBLE: no-op — adv-instance callback is passed at configure time). ext_adv_start() builds the extended (Broadcast Audio Service Data + Broadcast ID + complete name) and periodic (BASE from esp_ble_audio_bap_broadcast_source_get_base()) payloads in host-agnostic bytes, then calls adv_start(ext_data, ext_len, per_data, per_len). The host-specific implementation in main/bluedroid/adv.c or main/nimble/adv.c configures non-connectable extended adv (1M primary / 2M secondary, 200 ms interval), configures periodic adv (100 ms), writes both payloads, and starts periodic and extended advertising.
broadcast_start() calls esp_ble_audio_bap_broadcast_adv_add() and esp_ble_audio_bap_broadcast_source_start() on the same ADV_HANDLE, which kicks off BIGInfo + BIS creation.
When each BIS stream goes streaming, stream_started_cb allocates an SDU-sized buffer and calls example_audio_tx_scheduler_start() at preset_active.qos.interval; the scheduler invokes broadcast_source_tx(), which fills the buffer with the low byte of seq_num and calls esp_ble_audio_bap_stream_send().
stream_sent_cb forwards completions to example_audio_tx_scheduler_on_sent() for drift accounting; stream_stopped_cb and stream_disconnected_cb stop the scheduler; source_stopped_cb frees all per-stream buffers.

Expected Log

I (xxx) BAP_BSRC: Creating broadcast source: ... subgroup(s), ... stream(s)/subgroup
I (xxx) BAP_BSRC: Advertising started (handle 0)
I (xxx) BAP_BSRC: Broadcast source started
I (xxx) BAP_BSRC: [SRC #0] Stream started
I (xxx) BAP_BSRC: [SRC #1] Stream started

Periodic TX accounting (emitted by example_audio_tx_scheduler_on_sent under the BAP_BSRC tag, name SRC #<idx>) follows. On teardown:

I (xxx) BAP_BSRC: [SRC #0] Stream stopped, reason 0x...
I (xxx) BAP_BSRC: [SRC #0] ISO disconnected, reason 0x...
I (xxx) BAP_BSRC: Broadcast source stopped, reason 0x...

Peer Pairing

Run broadcast_sink on a second board. Expected interaction sequence:

Source advertises extended PDU containing the Broadcast Audio Announcement Service UUID, Broadcast ID 0x123456, and complete name "BAP Broadcast Source"; sink scans and matches by name + UUID.
Source's periodic advertising carries the encoded BASE; sink establishes PA sync and parses the BASE to recover subgroup count and BIS index bitfield.
Source's BIGInfo advertises the BIG as encrypted (broadcast code "1234"); sink reports BIG encrypted.
Source starts the BIG and the two BIS streams (FRONT_LEFT, FRONT_RIGHT); sink calls esp_ble_audio_bap_broadcast_sink_sync() with the chosen BIS bitfield and the matching broadcast code.
Source's TX scheduler keeps pushing SDUs at preset_active.qos.interval; sink stream recv callbacks deliver the data and update RX metrics.
Stopping the source (or losing PA sync) triggers stream_stopped_cb on the sink, which deletes the broadcast sink and resumes scanning.