nRF5340 LE Audio simultaneously two audio connections, one as peripheral to connect to phone and the other as central to connect to TWS earbuds ?

[Aakash MALVIYA]

New to audio LE but familiar with regular BLE connections to nRF52 series and nRF5340.

We are evaluating a new product concept.

My question is:

We have three devices in the scenario:

Device A is an nRF5340.

Device B is a smartphone.

Device C is off-the-shelf TWS (True Wireless Stereo) Earbuds which also has mic. 

Q1: Is it possible for the nRF5340,

acting as a peripheral, to receive an audio stream from the smartphone and send mic recording back to smartphone 

while simultaneously

functioning as a central device to send an audio stream to the TWS earbuds and receive mic recording from the earbuds?

If yes, will there be a drop in packets, or will it work normally for listening audio and talking?

if no, then what is possible in the scenario?

Q2: Does the scenario presented in Q1 have anything to do with Bluetooth 5 specifications, or does it depend on chipset capabilities?

[Maria Gilje]

Hello,

New to audio LE but familiar with regular BLE connections to nRF52 series and nRF5340.

Since you are new to LE Audio, I recommend that you read our documentation for the nRF5340 Audio application. This, together with the nRF5340 Audio DK, is the recommended starting point for developing LE Audio on Nordic devices.

Device C is off-the-shelf TWS (True Wireless Stereo) Earbuds which also has mic. 

Note that among the TWS Earbuds which are on the marked today, most -- if not all -- of them uses Bluetooth Classic and are not compatible with an LE Audio only device.

A1: In the nRF5340 Audio application it is possible to enable a bidirectional mode. The nRF5340 working as a gateway can have up to two headsets connected. Each device can switch between being the initiator* and the acceptor*. One aspect to take into concern is the processing power. Two mono bidirectional connections should be fine (encoding and decoding two streams), but stereo may not be possible (encoding and decoding four streams).

*The terminology used with LE Audio differs from regular Bluetooth LE, and I recommend that you take a look at Introducing Bluetooth LE Audio by Nick Hunn to understand the similarities and differences between Bluetooth LE and LE Audio.

A2: It is a combination. The topology is based on the LE Audio specification and the amount of possible devices connected is limited by the RAM on the nRF5340 as well as the Bluetooth LE controller used.

Best regards,

Maria

[StijnGerbranda]

Maria Gilje said:

Note that among the TWS Earbuds which are on the marked today, most -- if not all -- of them uses Bluetooth Classic and are not compatible with an LE Audio only device.

Dear Maria,

Is there a way to test if connecting with an earbuds device is definitely possible or not?

In my case, I have a Nordic nRF5340 audio development kit that I want to connect to a device that can play audio and has a mic. Preferably, these are earbuds.

I have tried it with the Philips TAT3508 (https://download.p4c.philips.com/files/t/tat3508bk_00/tat3508bk_00_dfu_nld.pdf) . Which should have LE support.

When looking at the nRF Connect app, the earbuds have LE and BR/EDR capabilities. But does this confirm that it is possible or is this inconclusive?

Regards,
Stijn

[bstewart-cae]

Theoretically possible in RF bandwith, but the application core is not fast enough to encode and decode that many LC3 channels and stay within the timing constraints.

[StijnGerbranda]

And sending the data from the nRF5340 audio development kit directly to the earbuds?

And can the BLE chip be used to send infomration over the RF bandwith?

[Maria Gilje]

Hello!

Apologies for the delay.

StijnGerbranda said:

I have tried it with the Philips TAT3508 (https://download.p4c.philips.com/files/t/tat3508bk_00/tat3508bk_00_dfu_nld.pdf) . Which should have LE support.

I agree, these earbuds seem to be LE Audio compatible. You are welcome to test your application with these, but please take into account that our LE Audio application is experimental. Some features may not work as expected. We appreciate if you share issues you run into while testing.

Thank you for contributing, bstewart-cae.

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StijnGerbranda said:

And sending the data from the nRF5340 audio development kit directly to the earbuds?

Do you mean to forward an already encoded audio stream from the Audio DK to the earbuds? This should not be too heavy on the CPU, so it is possible, yes. You need to implement this "pass through" mode though. As far as I know it is not part of any existing applications or samples in NCS/Zephyr.

StijnGerbranda said:

And can the BLE chip be used to send infomration over the RF bandwith?

Right now, we have a dedicated Bluetooth LE controller for Audio, which does not have the full functionality of the SoftDevice Controller or the Zephyr Controller. So we may be limited here. What information do you want to be able to send?

BR,

Maria