Hi there
I'm using the HCI UART bridge from NCS v3.2.1 in zephyr/samples/bluetooth/hci_uart with the provided overlay-all-bt_ll_sw_split.conf on an nRF54L15Dk and our Bluetooth Host stack: https://github.com/bluekitchen/btstack/)
While doing throughput tests with a 200 bytes MTU over GATT against the PTS / BL654 with PacketCraft Controller, I've wondered about the lower-than-expected data-rate.
Inspection of the HCI log of the nRF54l15 as Peripheral shows that the DLE is enabled in general as the SoftDevice reports TX Len 251 and TX Time 2704 us for the HCI Read Maximum Data Length.
We then use the LE Write Suggested Default Data Length with these values to set them as default. However, there's no HCI Event Data Length Change event later when the connection gets established.
Following the https://academy.nordicsemi.com/courses/bluetooth-low-energy-fundamentals/lessons/lesson-3-bluetooth-le-connections/topic/blefund-lesson-3-exercise-2/ I was also sending the HCI LE Set Data Length Command although that should not be necessary due to the earlier LE Write Suggested Default Data Length.
As a comparison, I've replaced the nRF54L15 with a second PTS dongle, where DLE gets activated as expected.
I've attached two zips with logs: one with PTS -> PTS and one with PTS -> nRF54L15. In the zips are the HCI trace as .pklg for Wireshark as well as the console log which also shows how to compile and run our examples. I've also include the .config File from the west built.
Why is DLE not working here? Do you have an HCI trace that shows a working DLE setup for comparison?
Thanks & best regards,
Matthias
