Connecting NRF5340 to ear buds

[Richard Taft]

Hello,

I am new to Bluetooth. I have two nrf5340 LE Audio SDKs which I have been able to configure and use as gateway and headset (walkie talkie, USB, and line-in, CIS and BIS). Now the next step is I want to connect the gateway to a third party headset or ear bud to stream audio. I connected the gateway to the serial terminal on my PC through NRF connect which prints out the following at startup. I have not been able to connect to any earbuds (classic or BLE). I have tried earbuds with BT 5.0, 5.1, and 5.3. Seems the gateway needs to provide a list of connectable devices to choose from. How is this done?

*** Booting nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***
GW [00:00:00.269,836] <inf> board_version: Compatible board/HW version found: 1.0.0
GW [00:00:00.304,321] <inf> sd_card: SD card volume size: 30941380608 B
GW [00:00:00.308,166] <inf> fw_info:
nRF5340 Audio nRF5340 Audio DK cpuapp
NCS base version: 2.9.0
Cmake run : Tue Mar 04 09:59:45 2025
GW [00:00:00.308,166] <inf> fw_info: ------- DEBUG BUILD -------
GW [00:00:00.308,166] <inf> fw_info: Compiled for GATEWAY device
GW [00:00:00.338,500] <inf> bt_mgmt_ctlr_cfg: Controller: SoftDevice: Version 6.0 (0x0e), Revision 8299
GW [00:00:00.338,714] <inf> bt_mgmt: Local identity addr: CF:33:22:1D:A1:B8 (random)
GW [00:00:00.366,882] <inf> broadcast_source: Enabling broadcast_source 0
GW [00:00:00.369,567] <inf> main: Broadcast source: NRF5340_BROADCASTER started
GW [00:00:00.370,666] <inf> bt_mgmt_adv: Local addr: 35:E1:69:8E:57:04 (random)
GW [00:00:00.372,711] <inf> main: Ext adv ready
GW [00:00:00.373,443] <inf> bt_mgmt_adv: Advertising successfully started
GW [00:00:00.381,286] <inf> broadcast_source: Broadcast source 0x2000da8c started
GW [00:00:00.381,317] <inf> le_audio: LC3 codec config for source:
GW [00:00:00.381,317] <inf> le_audio: Frequency: 48000 Hz
GW [00:00:00.381,317] <inf> le_audio: Duration: 10000 us
GW [00:00:00.381,317] <inf> le_audio: Channel allocation: 0x1
GW [00:00:00.381,347] <inf> le_audio: Octets per frame: 120 (96000 bps)
GW [00:00:00.381,347] <inf> le_audio: Frames per SDU: 1
GW [00:00:00.381,774] <inf> broadcast_source: Broadcast source 0x2000dab4 started
GW [00:00:00.381,805] <inf> le_audio: LC3 codec config for source:
GW [00:00:00.381,805] <inf> le_audio: Frequency: 48000 Hz
GW [00:00:00.381,805] <inf> le_audio: Duration: 10000 us
GW [00:00:00.381,805] <inf> le_audio: Channel allocation: 0x2
GW [00:00:00.381,805] <inf> le_audio: Octets per frame: 120 (96000 bps)
GW [00:00:00.381,805] <inf> le_audio: Frames per SDU: 1
GW [00:00:00.409,301] <inf> audio_datapath: Drft comp state: CALIB
GW [00:00:00.509,277] <inf> audio_datapath: Drft comp state: INIT
GW [00:00:00.510,284] <inf> audio_datapath: Drft comp state: CALIB
GW [00:00:00.610,290] <inf> audio_datapath: Drft comp state: OFFSET
GW [00:00:01.010,559] <inf> audio_datapath: Drft comp state: LOCKED

Thank you,

Rich

[dejans]

Hi,

Which BLE earbuds have you tried to use?

Have you checked that your selected earbuds support LE Audio?

Best regards,
Dejan

[Richard Taft]

Yes, I have tried various ear buds that support Bluetooth 5.0, 5.1, 5.3, and today I tried 5.4. My understanding is that all of these are BLE using the LC3 Codec.

I have connected to my SDK using nRF Connect and J-Link. The J-Link connects to my SDK but the scanning function is disabled. It says "Note: no pre-compiled firmware is available for the selected device..." What pre-compiled firmware should I have?

Thank you,

Rich

[dejans]

Hi,

Which specific earbuds do you use?

Best regards,
Dejan

[Richard Taft]

The final product needs to be compatible with a variety of Bluetooth LE earbuds and headsets. That includes ones with microphones. Currently I am working with this set. 

www.amazon.com/.../B0DSKN15PV

[dejans]

Hi,

Richard Taft said:

What I want to do is connect my nRF5340 SDK Gateway to my earbuds, like the phone does. I can put my earbuds in pairing mode, but how do I put my SDK in scanning mode and pair to them?

The way to connect to Nordic broadcaster is to connect through phone using Auracast on the phone. You can check if your phone supports Auracast.

Best regards,
Dejan

[Richard Taft]

Neither my phone, nor my earbuds support Auracast. Broadcast (BIS) is not a requirement for this project. Shouldn't CIS mode connect without Auracast?

My initial goal is to simply stream audio from my SDK to my BT 5.4 earbuds. What is the process? I have been using nRF5340 SDKs but it seems there is not a lot of support other than the walkie talkie demo.

I also have a nRF52840 USB SDK which seems to be better supported. What is the process to connect this device to my earbuds and stream sound from my pc? I think it is running the original blinky demo program. What sample program should I use?

I am really getting frustrated with the complexity of doing the most basic Bluetooth service of all- streaming sound to earbuds or a speaker. Please send me a guide to doing this.

[PaKa]

Seems you have run into an issue with the way Bluetooth versions are being abused in marketing products. The Bluetooth version number is not directly linked to features in the product, it is the version of the spec the device was certified against.

For a feature to possibly be supported the device must be certified for a Bluetooth spec no older than the one that introduced the feature. Bluetooth LE Audio came with Bluetooth 5.2 so anything with a Bluetooth spec lower than 5.2 will for sure not support Bluetooth LE Audio. Any Bluetooth Audio support then is guaranteed to be Bluetooth Classic. A product may only support the main featrures from Bluetooth 2.0 but still be certified as a Bluetooth 6.0 product, that only means it is tested to conform to the latest spec, this means good for interoperability but doesn't say anything about features.

For a product marked with Bluetooth 5.2 or higher it MAY use Bluetooth LE Audio but it MAY also only support Bluetooth Classic. What it does support should be listed as features on the device if you are to be able to say for sure. The earbuds you linked to has no comments whatsover so impossible to say if they support Bluetooth Classic only or if they also support Bluetooth LE Audio.

If you have a phone supporting Bluetooth LE Audio then a nRF5340 Audio kit with the earbud sample running CIS will show up as a headset like normal and you can connect to it. If it doesn't then I would check if the phone actually supports Bluetooth LE Audio as not all phones do.