STM32F4

Work with WINUSB as an USB CDC Device.

USB can transmit loop back message which is more than 64 bytes (firstly sent to ENDPOINT as DATAOUT then transmitted to HOST as DATAIN).

Reference:

1.This book "The Definitive Guide to ARM Cortex-M0 and Cortex-M0+ Processors" can offer general cortex knowledge.

https://www.sciencedirect.com/book/9780128032770/the-definitive-guide-to-arm-cortex-m0-and-cortex-m0-and-processors

2.This youtube video is an official STM32 tutorial video explaining how to have a skeleton of this project using Keil and CobeMX. 

https://youtu.be/h9T0RTu9Muc

3.This blog is an independent developer explaining how to modify your Keil project and in order to use winusb.sys as your STM32 board's device driver, he uses STMStudio and I read it and port it into my Keil project.

https://damogranlabs.com/2018/02/stm32-usb-cdc/

4.Microsoft doc explains how to use their WINUSB API to have applications communicate with an "winusb" device (a device recognized by WINDOWS as a device using winusb.sys as your STM32) board's device driver).

https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/winusb

https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/using-winusb-api-to-communicate-with-a-usb-device