This example demonstrates a raw BLE Isochronous Broadcast Receiver — it joins a Broadcast Isochronous Group (BIG) directly at the ISO transport layer over the NimBLE host, without any BLE Audio profile (BAP/CAP) on top.

The device acts as the receiver (BIG sync sink): it scans for an extended advertiser by device name, synchronises to the peer's periodic advertising train, parses the BIGInfo report, and then issues LE BIG Create Sync to join two BIS sub-events. An HCI output data path is installed on each BIS and incoming SDUs are accounted for by a small RX-metrics helper.

The payloads received are application-supplied dummy data produced by big_broadcaster; this example does not decode LE-Audio / LC3 — the coding format on the data path is ESP_BLE_ISO_CODING_FORMAT_TRANSPARENT.

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:

TARGET_DEVICE_NAME — "BIG Broadcaster" (matched against the AD complete-name field)
TARGET_BROADCAST_CODE — "1234" (must match the broadcaster)
SCAN_INTERVAL / SCAN_WINDOW — 100 ms / 100 ms (passive)
PA_SYNC_TIMEOUT — 10 s
BIG_SYNC_TIMEOUT — 1 s
BIS_ISO_CHAN_COUNT — 2

Security & Pairing

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). These settings are not exercised by this example — the receiver passively syncs to PA + BIS without ATT or pairing.

Build & Flash

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

(Exit serial monitor with Ctrl-].)

Example Flow

NVS, NimBLE host, and the ISO common layer are initialised; a GAP application callback is registered for ISO-related GAP events.
Passive extended scanning is started via ble_gap_disc().
On each EXT_SCAN_RECV the AD payload is parsed; if the complete-name field equals "BIG Broadcaster" and the report carries a non-zero periodic-advertising interval, ble_gap_periodic_adv_sync_create() is called.
On PA_SYNC success the extended scan is cancelled (BIGInfo arrives over the PA channel anyway).
On the first BIGINFO_RECV event the receiver fills esp_ble_iso_big_sync_param_t (both BIS in bis_bitfield, broadcast code "1234", MSE = nse from BIGInfo) and calls esp_ble_iso_big_sync() — the HCI LE BIG Create Sync command.
When each BIS becomes ready, the connected callback resets that BIS's RX metrics and installs an HCI output data path (ESP_BLE_ISO_DATA_PATH_DIR_OUTPUT, transparent coding).
Each recv callback updates the per-BIS counters; one log line is emitted every LOG_INTERVAL_PACKETS SDUs.
On BIS disconnect or PA-sync-lost the receiver clears its sync state and restarts extended scanning.

Expected Log

Tag: BIG_SNC.

Discovery and PA sync:

I (xxx) BIG_SNC: Scanning for broadcaster...
I (xxx) BIG_SNC: PA synced: handle <h> sid <s> phy <p> peer xx:xx:xx:xx:xx:xx

BIS bring-up:

I (xxx) BIG_SNC: [BIS #0] Connected
I (xxx) BIG_SNC: [BIS #1] Connected

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

I (xxx) BIG_SNC: [BIS #0] RX: <N> packets
I (xxx) BIG_SNC: [BIS #1] RX: <N> packets

Teardown / re-sync (broadcaster disappears or restarts; reason 0x08 is the typical timeout, 0x3D is the rare MIC-fail race documented in source):

I (xxx) BIG_SNC: [BIS #0] Disconnected, reason 0x08
I (xxx) BIG_SNC: [BIS #1] Disconnected, reason 0x08
I (xxx) BIG_SNC: PA sync lost: sync_handle <h> reason 0x<rr>
I (xxx) BIG_SNC: Scanning for broadcaster...

Peer Pairing

Run big_broadcaster on a second board.

Flash and run big_broadcaster on board A; it begins extended + periodic advertising and creates the BIG.
Flash and run big_receiver on board B; it logs Scanning for broadcaster... and waits.
Board B matches the AD name "BIG Broadcaster", creates a PA sync, logs PA synced, and stops the extended scan.
On the first BIGInfo report, board B issues LE BIG Create Sync with broadcast code "1234" and both BIS selected; both sides log [BIS #0/1] Connected.
Per-BIS RX-packet milestones are logged on B at the same cadence that A logs TX milestones.
Resetting board A causes B to log a BIS disconnect and PA sync lost, then automatically restart scanning to re-pair.