SPBTLE-RF direct mode

Hello, we have developed a device based on SPBTLE-RF and stm32L452.

To certify the device we have to operate BLE modules in direct mode. If I understand correctly DT0069, hci is only on SPI and we should forward on the UART.

Are there any code examples for stm microcontrollers which forward hci interface on the UART?

Many Thanks.