[M451] Use SPI Flash as USB MSC Device

Application: The microcontroller plays a role of USB mass storage device and uses SPI Flash as a storage medium.
BSP Version: M451 Series BSP CMSIS V3.01.003
Hardware: NuTiny-EVB-M451-LQFP100 V1.3
The microcontroller M451 connects to the computer via a USB port, plays a role of a mass storage class device, and connects an external SPI Flash Memory as a medium. The user can use the microcontroller as a general external USB flash drive to write and read files on a personal computer.

You can download the sample code at https://www.nuvoton.com/resource-downlo ... 1211153528