Zephyr HCI USB sample unable to build with "legacy" and extended advertising support.

[HanskampTom]

I'm currently trying to configure the Zephyr HCI USB sample to allow using legacy and extended advertising. Currently when I build the sample with extended advertising enabled and I issue a legacy advertising HCI command I always get a response of COMMAND_DISALLOWED. When I change the config to not build with extended advertising the HCI command works and I can see the advertisements. Is my configuration wrong, or is this not possible.

I'm using NCS v2.8.0 with the following prj.conf for the HCI USB sample:

CONFIG_BT=y
CONFIG_BT_HCI=y
CONFIG_BT_HCI_RAW=y
CONFIG_BT_LL_SOFTDEVICE=y
CONFIG_BT_CTLR_ADV_EXT=y
CONFIG_BT_EXT_ADV=y

CONFIG_USB_DEVICE_STACK=y
CONFIG_USB_DEVICE_PID=0x000B
CONFIG_USB_DEVICE_BLUETOOTH=y
CONFIG_USB_DEVICE_BLUETOOTH_VS_H4=n
CONFIG_USB_DEVICE_INITIALIZE_AT_BOOT=n

# We dont want any console or CDC ACM that may cause BlueZ to not detect hci_usb
CONFIG_SERIAL=n
CONFIG_CONSOLE=n
CONFIG_UART_CONSOLE=n

# Workaround: Unable to allocate command buffer when using K_NO_WAIT since
# Host number of completed commands does not follow normal flow control.
CONFIG_BT_BUF_CMD_TX_COUNT=10

Below see the output of btmon on the host that is issuing the HCI commands.

[Kenneth]

Hello,

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. We plan to add a disclaimer to the hci_usb sample. A suggested workaround is to use compile hci_uart with the cdc uart driver instead (if you need to use usb, and cant use uart or spi directly). 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). Please see how this can be done for the nRF52840 here:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.5.2/zephyr/samples/bluetooth/hci_uart/README.html#using-a-usb-cdc-acm-uart 

Kenneth

[HanskampTom]

Than for the fast response, I will try the USB CDC UART route in a few days and will report back.