I've implemented a USB Host CDC protocol structure on STM32L4 controller which I want to connect to an Android Phone. I want Android to run in Device Mode (Not in Host mode which UsbSerial library uses!) CDC class so that it's USB protocol Class Code can match to the STM32's USB Class Code but when I connect it phone my phone do not provide me any option as CDC/ACM.

It only shows:

Charging only. (Class Code: 0xFF)

MTP. (Class Code: 0x8)

PTP. (Class Code: 0x6)

So, is there any way I can switch Android to CDC as Device mode by writing an app?

Also, can implementing AOA protocol on my Host side solve this problem?