nRF 5340 Audio DK - PHY coding

[Lars.Bjok]

Hello!

I am curently evaluating the nRF5340 Audio DK. I'm having trouble testing different PHY coding setting (2Mbps, 1Mbps, ,500kbps and 125kbps) using the nrf5340_audio application provided by Nordic Semiconductor. I am currently using three DKs one as a transmitter and two as receivers.

After investigating the issue, i've noticed that configuration such as CONFIG_BT_CTLR is not compatible with the DK. 

The goal for this evaluation is to see how different PHY codings affect the LE audio streaming. Any help would be greatly appreciated

Regards, Lars

[SwRa]

HI Lars,

I heard back from the developers.. This is what they said:

"Following are details of PHY in CIS demo:

1. In NCS v2.3.0, ADV-EXT is used for headset advertisement, so once if gateway connected with a headset, the ACL will use 2M PHY as default. User can try to send PHY update from either side for changing the PHY for ACL to 1Mbps for a trial.
2. For PHY in ISO, that is decided by gateway, and it is 2M in the default setting.
   In the current code, the gateway will use a preset configuration for codec and QoS setting, which is in here
   https://github.com/nrfconnect/sdk-nrf/blob/8f26142b2f815d5a12e1f77ee8a6ea554a89b079/applications/nrf5340_audio/src/bluetooth/le_audio_cis_gateway.c#L93
   
   However, if we trace the code a little further bit, we will find the PHY is fixed in here:
   https://github.com/nrfconnect/sdk-zephyr/blob/74c7bca86e6a7d590333681eef90e159d79bcfe8/include/zephyr/bluetooth/audio/audio.h#L373
   So customer can try to create a preset by self (that would be better), or do a quick trial to modify the above line for assigning the PHY to 1Mbps (not suggested)
3. Please note that
   a. We are focusing on using 2M PHY in ISO CIS, we are not well tested other options
   b. Coded PHY might not work properly, we haven't tested that, and that is not covered in the contract
   c. 1M PHY means slower than 2M PHY, so we cannot use the same bitrate anymore because of the bandwidth.
   (CONFIG_BT_AUDIO_BITRATE_UNICAST_SINK=32000, which means 40 bytes per frame works for 1M CIS ISO)"

Hope this helps.

Regards,

Swathy

[JoeBakalor]

Hi SwRa , what about support for Coded PHY in BIS mode?