How to enable "LE Data Packet Length Extension"?

RE: How to enable "LE Data Packet Length Extension"?

cwhit — Wed, 26 Feb 2025 20:00:42 GMT

Okay, silly me. LE Audio likely doesn't need LE Data Packet Length Extension because this was an ACL feature long before the ISO channels of LE Audio came along.

Thanks,
Chris

RE: How to enable "LE Data Packet Length Extension"?

cwhit — Tue, 25 Feb 2025 20:15:50 GMT

Hi Einar,

I am using NCS 2.9.0 with the nRF5340 audio application built as a unicast_server. The ADK is not setting the LE Data Packet Length Extension bit in the LL features. See attached screenshot from Ellisys. (Note that Ellisys misnames this by not including the word "Packet.") In case you're wondering, the Central I'm using does set this bit.

I have made these related changes to the config set and expect that's all it should take:
Host layer:
CONFIG_BT_DATA_LEN_UPDATE=y
CONFIG_BT_USER_DATA_LEN_UPDATE=y

Controller layer (ipc_radio prj.conf):
CONFIG_BT_CTLR_DATA_LENGTH_MAX=251

These changes seem to align with the Throughput example you cited. All it has are:
CONFIG_BT_CTLR_DATA_LENGTH_MAX=251 and CONFIG_BT_USER_DATA_LEN_UPDATE=y in the application prj.conf, and...
CONFIG_BT_CTLR_DATA_LENGTH_MAX=251 in the ipc_radio prj.conf. (Seems odd that this is duplicated.)

What am I missing? Can you explain why this controller feature bit isn't set? And, shouldn't LE Data Packet Length Extension be enabled by default for the audio application? I'd expect it to be required for LE Audio in general.

Also, what's the difference between CONFIG_BT_DATA_LEN_UPDATE and CONFIG_BT_USER_DATA_LEN_UPDATE?

Thanks,
Chris

RE: How to enable "LE Data Packet Length Extension"?

Torsten Robitzki — Thu, 20 Feb 2025 09:09:49 GMT

Hi Einar Thorsrud

that helps a lot.

best regards

Torsten

RE: How to enable "LE Data Packet Length Extension"?

Einar Thorsrud — Wed, 19 Feb 2025 13:20:45 GMT

Hi,

Regarding CONFIG_BT_USER_DATA_LEN_UPDATE, this is a configuration that only apply to the Bluetooth host, so it should not be in hci_ipc.conf (network core configuration). You can refer to the Throughput sample for the configuations for DLE showing this (and other adjustments for increased throughput, such as larger event length and buffer sizes).