I am testing HCI UART and HCI USB to use nRF5340DK as a Bluetooth Controller for RPI400. While HCI USB is working well as expected, I have trouble bringing up HCI UART.
Test setup
- Unmodified nRF5340DK is connected to RPI400's USB port via the interface MCU's USB connector (J2).
- Used the sample located in "zephyr\samples\bluetooth\hci_uart" of the unmodifed nRF Connect SDK (tested with v1.5.0 and v1.5.1-rc1).
- Compiled and flashed using the following command: "west build -b nrf5340dk_nrf5340_cpuapp & west flash"
Test log
- The following is the screenshot, showing the steps I used to bring up the HCI UART interface.

Is there anything I am missing?