[M252] DFU Dual Interface ISP

Application	This example code uses M252 USBD to implement a dual-interface DFU device to update APROM and SPI Flash.
BSP Version	M251_M252_M254_M256_M258_Series_BSP_CMSIS_V3.02.008
Hardware	NuMaker-M252KG V1.4 and external SPI Flash

This example code demonstrates a USB DFU (Device Firmware Upgrade) ISP implementation
executed on the internal LDROM of the NuMicro M252 series microcontroller. It enables
firmware update for both the internal APROM and external SPI Flash memory through a
standard USB DFU interface.

• This example code requires additional hardware and software modules:
  Standard SPI Flash with four signals: /SS, CLK, MOSI and MISO.
  e.g. Winbond W25Q32 SPI Flash.
• DFU utility for firmware download/upload operations.
  https://dfu-util.sourceforge.net/
• Windows driver provides USB drivers for DFU device recognition.
  

You can download the sample code at EC_M252_DFU_Dual_Interface_ISP_V1.00