使用STM32cube配置好相关引脚，开启USB的Mass Storage Class功能

USB_DEVICE中的MSC_MEDIA_PACKET可以设置大一点，增大缓冲区可以提高速度，对于外部spi-flash来说，要大于4096bytes

增加堆栈大小，否则USB无法正常工作

usbd_storage_if.c添加代码：

#define     FLASH_START_ADDR        0x08010000    // 

#define     FLASH_PAGE_NBR              90       // 30K

int8_t STORAGE_GetCapacity_FS(uint8_t lun, uint32_t *block_num, uint16_t *block_size)

{

  /* USER CODE BEGIN 3 */

 if(lun == 0)

 {

  *block_num  = FLASH_PAGE_NBR;

  *block_size = FLASH_PAGE_SIZE;

  }

  return (USBD_OK);

  /* USER CODE END 3 */

}

int8_t STORAGE_Read_FS(uint8_t lun, uint8_t *buf, uint32_t blk_addr, uint16_t blk_len)

{

  /* USER CODE BEGIN 6 */

 if(lun == 0)

 {

    memcpy(buf,(u8 *)(FLASH_START_ADDR + blk_addr*FLASH_PAGE_SIZE),blk_len*FLASH_PAGE_SIZE);

    return USBD_OK;

  }

  return USBD_FAIL;

  /* USER CODE END 6 */

}

int8_t STORAGE_Write_FS(uint8_t lun, uint8_t *buf, uint32_t blk_addr, uint16_t blk_len)

{

  /* USER CODE BEGIN 7 */

  if(lun == 0)

  {

    uint16_t i;

HAL_FLASH_Unlock();

FLASH_EraseInitTypeDef f;

f.TypeErase = FLASH_TYPEERASE_PAGES;

f.PageAddress = FLASH_START_ADDR + blk_addr*FLASH_PAGE_SIZE ;

f.NbPages = blk_len;

uint32_t PageError = 0;

HAL_FLASHEx_Erase(&f, &PageError);

  for(i=0;i

HAL_FLASH_Program(FLASH_TYPEPROGRAM_WORD,FLASH_START_ADDR + blk_addr*FLASH_PAGE_SIZE + i , *(u32 *)(&buf[i]));

HAL_FLASH_Lock();

    return USBD_OK;

   }

   return USBD_FAIL;

  /* USER CODE END 7 */

}

对于USB D+有上拉电阻控制的方案，要USB初始化中加入控制