This example demonstrates a raw BLE Isochronous Broadcaster — it creates a Broadcast Isochronous Group (BIG) directly at the ISO transport layer over either the NimBLE or Bluedroid host (selected at build time via Kconfig), without any BLE Audio profile (BAP/CAP) on top.

The device acts as the broadcaster: it starts extended + periodic advertising, creates a BIG carrying two BIS streams, sets up an HCI input data path on each BIS, and then transmits SDUs on a fixed 10 ms cadence using a software TX scheduler. The peer (big_receiver) discovers the broadcaster by name, syncs to the periodic advertising train, decodes BIGInfo, and joins the BIS sub-events.

The audio data on the wire is application-supplied dummy payload (each SDU is filled with the byte value of its sequence number). The coding format is ESP_BLE_ISO_CODING_FORMAT_TRANSPARENT, so no LC3 / LE-Audio framing is involved.

Requirements

A board with BLE 5.2 and ISO support (e.g. ESP32-H4, ESP32-S31)
Peer device running the paired example

Configuration

idf.py menuconfig

No build-time options — runtime defaults are baked into source.

Notable hard-coded parameters in main/main.c:

LOCAL_DEVICE_NAME — "BIG Broadcaster" (advertised in extended adv)
LOCAL_BROADCAST_CODE — "1234" (BIG is encrypted)
BIG_SDU_INTERVAL_US — 10 000 us
BIG_LATENCY_MS — 10 ms
BIG_PHY — 2M
BIG_RTN — 2 (retransmissions)
BIS_ISO_CHAN_COUNT — 2
BIS_SDU_SIZE — 120 bytes

Security & Pairing

On the NimBLE path, the shared init at ../common_components/example_init/ble_iso_example_init.c configures Just-Works pairing (LE Secure Connections, no MITM, BLE_SM_IO_CAP_NO_IO) with bonding enabled, and leaves gatts_register_cb = NULL (no GATT services). On the Bluedroid path the same init just brings up the controller and host with no SMP configuration. Either way these settings are not exercised by this example — BIG broadcast traffic is non-connectable and BIS payload encryption is driven by the broadcast code, independent of host SMP.

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

NVS, the selected BLE host (NimBLE or Bluedroid), and the ISO common layer are initialised.
A TX scheduler is initialised for each of the two BIS channels.
Extended advertising parameters / data and periodic advertising parameters / data are configured for handle 0 (non-connectable, non-scannable, primary 1M / secondary 2M).
Periodic advertising and extended advertising are started.
esp_ble_iso_big_ext_adv_add() ties the adv handle to the BIG, then esp_ble_iso_big_create() issues the HCI LE Create BIG with two BIS, encryption on, and broadcast code "1234".
As each BIS becomes ready, the connected callback installs an HCI input data path (ESP_BLE_ISO_DATA_PATH_DIR_INPUT, transparent coding).
Once both BIS are connected, the per-channel TX schedulers start firing every 10 ms, calling esp_ble_iso_chan_send() with a 120-byte dummy SDU and an incrementing sequence number.
On disconnect of all BIS the schedulers are stopped and the BIG handle is cleared.

Expected Log

Tag: BIG_BRD.

Startup / advertising:

I (xxx) BIG_BRD: Advertising started (handle 0)

BIS bring-up (first BIS, then second, then TX start):

I (xxx) BIG_BRD: [BIS #0] Connected
I (xxx) BIG_BRD: Waiting for remaining BIS channels (1/2)
I (xxx) BIG_BRD: [BIS #1] Connected
I (xxx) BIG_BRD: All 2 BIS channels connected, starting TX

Steady-state (logged every LOG_INTERVAL_PACKETS SDUs by the shared TX helper):

I (xxx) BIG_BRD: [BIS #0] TX: <N> packets
I (xxx) BIG_BRD: [BIS #1] TX: <N> packets

Teardown:

I (xxx) BIG_BRD: [BIS #0] Disconnected, reason 0x<rr>
I (xxx) BIG_BRD: [BIS #1] Disconnected, reason 0x<rr>
I (xxx) BIG_BRD: All BIS channels disconnected, TX stopped

Peer Pairing

Run big_receiver on a second board.

Flash and run big_broadcaster on board A; it begins extended + periodic advertising and creates the BIG immediately.
Flash and run big_receiver on board B; it starts passive extended scanning.
Board B matches on the device name "BIG Broadcaster" and creates a periodic advertising sync to the broadcaster's PA train.
Once PA-synced, board B receives the BIGInfo report and calls LE BIG Create Sync with broadcast code "1234" and both BIS in the bitfield.
Board A logs [BIS #0/1] Connected as the controller reports the BIS as established; board B logs PA synced followed by per-BIS Connected and starts counting received SDUs.
Resetting either side causes the receiver to drop and (via pa_sync_lost) restart its scan, re-establishing the link automatically.