HCI USB sample: packets per connection interval

RE: HCI USB sample: packets per connection interval

boborjan — Tue, 16 Jun 2026 16:47:07 GMT

This is the dongle I used for ble sniffing. I get another one and take a log.

RE: HCI USB sample: packets per connection interval

Kenneth — Tue, 16 Jun 2026 16:29:31 GMT

Do you by any chance have an on-air sniffer log?
https://academy.nordicsemi.com/courses/bluetooth-low-energy-fundamentals/lessons/lesson-6-bluetooth-le-sniffer/

I am not that familiar with HCI logs.

Kenneth

RE: HCI USB sample: packets per connection interval

boborjan — Tue, 16 Jun 2026 16:13:12 GMT

Can you perhaps suggest usb dongle that is surely capable of high ble throughput? Just to make sure my system is capable of the task.

Chipsets I have tried:

rtl8761bu -> does not support even DLE (keeps sending 27byte packets) on Linux

BCM20702A1 -> same, packet length is 27 bytes

RE: HCI USB sample: packets per connection interval

boborjan — Mon, 15 Jun 2026 17:47:44 GMT

Analysing the logs I figured the min/max ce length setting is not ok. I modified on opponent side to 7.5ms/15ms and the behavior got better but it's still far from the limit.devzone.nordicsemi.com/.../nrf52840_5F00_hciuart_5F00_ce.pcapng.gz

RE: HCI USB sample: packets per connection interval

boborjan — Mon, 15 Jun 2026 15:42:18 GMT

Hi Kenneth,

thanks for the prompt answer. I tried the setup with hci_uart (dle enabled, mtu 251). Interestingly I get the very same result (see attached pcap). I also tried highering BT_CTLR_SDC_RX_PACKET_COUNT/BT_CTLR_SDC_TX_PACKET_COUNT for the hci_usb sample without improvement.

I also applied the config changes from ipc_radio/prj.conf with the same results (note CONFIG_BT_CTLR_DATA_LENGTH_MAX is not present in v3.3 kconfig)

Viktordevzone.nordicsemi.com/.../nrf52840_5F00_hciuart.pcapng.gz

RE: HCI USB sample: packets per connection interval

Kenneth — Mon, 15 Jun 2026 11:56:07 GMT

Hello,

First, I get the impression that hci over usb as a transport layer is slightly unstable by design; for simple use cases where transfer is not stressed then hci_usb is functional, but for stability you should use uart or spi as hci transport. It seems as most vendors use uart hci transport due to this, e.g. in phones, laptops etc. A suggested workaround is to compile hci_uart with the cdc uart driver instead (if you need to use usb). It's possible to build the hci_uart with usb interface (using USB CDC as transport, this is not directly the same as hci_usb though, but it's stable and works). Please see how this can be done for the nRF52840 here:
https://nrfconnectdocs.nordicsemi.com/ncs/3.3.0/zephyr/samples/bluetooth/hci_uart/README.html#using-a-usb-cdc-acm-uart

The throughput example give some suggestions on kconfig options to increase throughput:
https://github.com/nrfconnect/sdk-nrf/blob/main/samples/bluetooth/throughput/sysbuild/ipc_radio/prj.conf

Kenneth

RE: HCI USB sample: packets per connection interval

boborjan — Mon, 15 Jun 2026 07:22:24 GMT

I forgot: I am using Linux (debian trixie), kernel 6.12.84, bluez 5.82.