最近做了一个USB工具，像U盘拷贝一样，升级STM32固件
手册链接如下所示
有朋友说amobbs下载不了文件，这里传一份吧
https://github.com/cedar-renjun/cedar-renjun.github.io/tree/master/assets/2015/12/3/USB_MSD_Bootloader.hex.zip
https://github.com/cedar-renjun/cedar-renjun.github.io/tree/master/assets/2015/12/3/USB_MSD_Updater_User_Manual.pdf
https://github.com/cedar-renjun/cedar-renjun.github.io/tree/master/assets/2015/12/3/USB_MSD_Bootloader_Usage.pdf