Coded phy with LE audio application

[Ahmed Moheb]

Hi,

I'm evaluating the LE audio application to check the capability of using the Coded PHY for transmitting audio.

According to this page, LE Isochronous Channels: Configurations for CIS, 1M PHY and CODED PHY are tested with bidirectional data transfer with two CISes configured with longer ISO intervals to accommodate for longer packet durations.

I followed the following 2 sample applications found with nRF Connect SDK to adjust the LE audio application for using the codec PHY

1. Bluetooth: Central Heart Rate Monitor with Coded PHY
2. Bluetooth: Peripheral Heart Rate Monitor with Coded PHY

The ACL connection between the boards was created successfully and I was able to get audio.

Now, I've a couple of questions

1. Does the central device create and maintain a new ISO connection that is independent form the ACL connection?
   This means that for every connected audio sink device, the audio source device will have 2 active connections linked to the aduio source device.
2. Assuming the answer to the first question is yes and there are 2 connections, How to verify that the ISO connection is using the coded PHY as well? or the ACL connection was made using the coded PHY, this should imply that the following ISO connection will be also using the codec PHY.

Thanks,

Ahmed

[AHaug]

Hi Ahmed,

I've picked up your case and will be looking into your query, however I will require some time.

I will get back to you with an update during the upcoming week. 

Kind regards,
Andreas

[AHaug]

Hi,

I have an update for you already

Does the central device create and maintain a new ISO connection that is independent form the ACL connection?
This means that for every connected audio sink device, the audio source device will have 2 active connections linked to the aduio source device.

This is correct, CIS does also require an ACL for control

Assuming the answer to the first question is yes and there are 2 connections, How to verify that the ISO connection is using the coded PHY as well? or the ACL connection was made using the coded PHY, this should imply that the following ISO connection will be also using the codec PHY.

A connection always inherits PHY from the PHY that's used in the advertising, but here it is strictly speaking a new connection thats being made without going through an ACL. To my understanding, the PHY is inherited also in this case, but I recommend you to verify this by printing debug logs from the Softdevice (it should be possible to get an output as it should be stated there)

Kind regards,
Andreas