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Getting Started with LE Audio

By the end of this tutorial your IPRO7AI Reef EVK runs ipro_le_audio_headset: it advertises as IPRO-LE-Audio, pairs with an LE Audio phone and offers the PACS, ASCS, CAS and VCP services among others. You change the VCP volume from the board's keys, check the speaker and headphone output with a test tone, and learn which settings an LE Audio application needs.

What this release has validated

According to the application's README, the app is a profile and ISO data-path bring-up, not a finished audio product:

  • Validated: a phone scans, connects, pairs (security level 4), discovers the LE Audio services (1853, 1850, 184e, 1844) and controls the volume over VCP.
  • Not yet validated: streaming music from a phone. Android currently reports no connected audio channels with this firmware. Playback of decoded LC3 audio and acoustic validation are also still open.

The test_tone command drives the DAC directly, not through an LE Audio stream.

Prerequisites

  • IPRO7AI Reef EVK with SW8 on PWR, powered from USB-C, with an IPRO Debug Probe or a 3.3 V USB-UART cable on U6 (115200 8N1; wiring in IPRO7AI Reef EVK). Headphones on J2 are optional.
  • First FreeRTOS Application done, and the IntelProCube 0.7.0.1 command-line flash tool installed as in Set Up Your Host.
  • A serial terminal in which you can type commands (see Flashing & Serial Console).
  • An Android phone that supports LE Audio, with LE Audio switched on. The phone recorded in the application README is a Pixel 10 Pro with Android 17.

Steps

  1. Build the Reef configuration:

    make -C apps/bluetooth/le_audio/ipro_le_audio_headset DEFCONFIG=defconfig_reef

    Output: apps/bluetooth/le_audio/ipro_le_audio_headset/build_reef/build_out/ipro_le_audio_headset_IPRO7.bin. This configuration links for 2 MB of flash (CONFIG_IPRO7_FLASH_2M=y). A plain make without DEFCONFIG= builds the IPRO7 EVB version.

  2. Flash: put the Reef in download mode (hold SW1, tap SW2, release SW1; if the board runs firmware with a shell, reboot_dl does the same), then run from the IntelProCube directory:

    ./ipro_iot_tool_macos --chipname ipro7 --chip-variant IPRO7AI \
    --port /dev/cu.usbserial-XXXX --baudrate 921600 \
    --firmware <SDK>/apps/bluetooth/le_audio/ipro_le_audio_headset/build_reef/build_out/ipro_le_audio_headset_IPRO7.bin

    ./ipro_iot_tool_linux --chipname ipro7 --chip-variant IPRO7AI \
    --port /dev/ttyUSB0 --baudrate 921600 \
    --firmware <SDK>/apps/bluetooth/le_audio/ipro_le_audio_headset/build_reef/build_out/ipro_le_audio_headset_IPRO7.bin

    .\ipro_iot_tool.exe --chipname ipro7 --chip-variant IPRO7AI `
    --port COM5 --baudrate 921600 `
    --firmware <SDK>\apps\bluetooth\le_audio\ipro_le_audio_headset\build_reef\build_out\ipro_le_audio_headset_IPRO7.bin

    The tool exits with 0 even when it fails, so check the output for [All Success].

  3. Open the console and reset: open the console at 115200 baud and tap SW2. The boot log includes these lines (level, time and thread fields omitted):

    MAIN: IPRO LE Audio Headset v2.0 (Zephyr blestack)
...
BLE_INIT: Advertising started: IPRO-LE-Audio
KEYS: Keys: SW3 vol-, SW4 vol+, SW5 mute (GPIO<n>/<n>/<n>)

  4. Check the audio output: type the command below to play a 1 kHz test tone for 3 seconds. With headphones in J2 the speaker amplifier is off and the tone plays only in the headphones.

    test_tone 3

  5. Pair the phone: in the phone's Bluetooth settings, pair a new device and pick IPRO-LE-Audio. The console prints:

    BLE_INIT: Connected: <phone address>
BLE_INIT: Security requested: level 2
BLE_INIT: Security changed: <phone address> level <n>
BLE_INIT: [SMP] Pairing complete: <phone address>, bonded=1

    The phone lists the board as an LE Audio device. The bond is stored in flash and survives a reboot.

  6. Change the volume from the keys: SW4 turns the volume up, SW3 down, and SW5 toggles mute. The keys go through the VCP volume renderer, so the volume slider on a connected phone follows. The console prints:

    VCP_SERVER: Volume state changed: volume=<0-255> mute=<0|1>

    Type vol to see the current volume.

  7. Check the status:

    leaudio_status

    It shows BLE Ready, the counts of received and decoded audio frames, the current sample rate and the output (DAC (Speaker)).

Streaming music from a phone

Streaming from a phone is not validated in this release (see the top of this page). If your source does set up a stream, the console prints Stream … started (Streaming state) and Frames Received in leaudio_status keeps rising; judge the result by what you measure.

Verify

  • The console prints Advertising started: IPRO-LE-Audio, and test_tone 3 is audible.
  • The phone pairs and the console prints Pairing complete: …, bonded=1. The services the phone discovers include CAS (0x1853), PACS (0x1850), ASCS (0x184E) and VCS (0x1844).
  • Pressing SW3, SW4 or SW5 prints Volume state changed on the console, and the phone's volume slider moves with it.

Key settings

LE Audio needs a controller library with ISO support and a larger Exchange Memory; on the host, you enable the profiles for your role. This excerpt is from defconfig_reef:

apps/bluetooth/le_audio/ipro_le_audio_headset/defconfig_reef (excerpt)
# Controller: peripheral ACL plus two ISO streams, Bluetooth 5.4 feature set
CONFIG_IPRO_BLE_CTLR_LIB="link1_periph"
CONFIG_IPRO_BLE_CTLR_FEATURE="bt54_iso2"
CONFIG_IPRO_BLE_CTLR_CFG_DBG=y
CONFIG_EM_SIZE=32
CONFIG_BT_CONN=1

# Pairing and bonding
CONFIG_BT_SMP=y
CONFIG_BT_SETTINGS=y
CONFIG_BT_BONDABLE=y

# LE Audio profiles
CONFIG_BT_AUDIO=y
CONFIG_BT_AUDIO_RX=y
CONFIG_BT_BAP_UNICAST_SERVER=y
CONFIG_BT_PACS=y
CONFIG_BT_ASCS=y
CONFIG_BT_VCP_VOL_REND=y
CONFIG_BT_CAP_ACCEPTOR=y
CONFIG_BT_CSIP_SET_MEMBER=y

# ISO channels
CONFIG_BT_ISO=y
CONFIG_BT_ISO_RX=y
CONFIG_BT_ISO_PERIPHERAL=y

# LC3 codec (prebuilt) and DAC output
CONFIG_COMPONENTS_LC3_ENABLE=y
CONFIG_BSP_USING_DAC=y
  • bt54_iso2 needs CONFIG_EM_SIZE of at least 32; otherwise the build stops at the configure step.
  • CONFIG_IPRO_BLE_CTLR_CFG_DBG=y selects the debug controller library; without it the _release library is used.
  • This application does not enable media control (MCP) or call control (CCP).

The Reef uses defconfig_reef only: the DAC drives the speaker and the J2 headphone jack (headphones in J2 switch the speaker amplifier off), and SW3, SW4 and SW5 change the volume through VCP. dac os 0|1|2 selects the DAC output path (the Reef default is 1, 512 kHz with noise shaping), and dac spk <dB> sets the gain of the speaker path. The app's .config, DAC.config and UAC.config are IPRO7 EVB configurations.

LE Audio terms

Term Meaning In ipro_le_audio_headset
CIS Connected isochronous stream, one to one, used by headsets Receiving end
BIS Broadcast isochronous stream, one to many (Auracast) Not used
BAP Sets up and manages audio streams Unicast server with 2 sink ASEs
PACS Publishes the supported codec capabilities LC3: 16 / 32 / 48 kHz, 7.5 / 10 ms, mono, 26–155 octets per frame
ASCS Configuration and state of the audio stream endpoints (ASEs) Enabled
VCP Volume control Volume renderer
CAP / CSIP Common audio profile / coordinated set CAP acceptor and CSIP set member
LC3 The standard LE Audio codec Prebuilt library

Troubleshooting

Symptom Cause Fix
IPRO-LE-Audio does not appear in the phone's Bluetooth list LE Audio is off on the phone, or the board is already connected to another device Switch on LE Audio on the phone; the application accepts one link at a time and stops advertising while connected
Pairing fails after reflashing The phone or the board kept an old bond Type leaudio_unpair at the console to clear the bonds, remove the device on the phone, and pair again
test_tone is silent The speaker is off while headphones are in J2; the amplifier runs from USB VBUS Unplug the headphones or listen on them; power the board over USB-C
A key press prints volume control not up yet VCP has not finished initializing Wait until the boot messages are done
The build stops at the configure step with a message about CONFIG_EM_SIZE bt54_iso2 needs a larger Exchange Memory Set CONFIG_EM_SIZE=32

Next steps