mass storage class and usbd_storage.c

[mentalmenza]

Posted on September 08, 2014 at 16:25

I try to make mass storage device with stm32f4 and I don't use SD card. So i take usb device example and change usbd_storage.c

#define STORAGE_LUN_NBR                  1  

#define STORAGE_BLK_NBR                  2048  

#define STORAGE_BLK_SIZ                  1

uint8_t Memory[2048];

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int8_t STORAGE_Init(uint8_t lun)

{

   int i = 0;

   for (i = 0 ; i < 2048 ; i++)

   {

      Memory[i] = 0;

  }

  return 0;

}

int8_t STORAGE_IsReady(uint8_t lun)

{

   return 0;

}

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

{

   int i;   

   for (i = 0; i < blk_len; i++)

   {

      buf[i] = Memory[i+blk_addr];

   }

  return 0;

}

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

{   

   int i;   

   for (i = 0; i < blk_len; i++)

   {

      Memory[i+blk_addr] = buf[i];

   }

  return 0;

}

I download program to STM32, connect it to PC, new disk appears in Windows Ecplorer and I can't access it, so it doesn't work as mass storage device. I know, that with global array Memory[] it will be erase after power off, but I thought that when it connected to PC, it should work fine.So what is wrong?I also don't understand what STORAGE_BLK_NBR and STORAGE_BLK_SIZ should be exactly?

[Tesla DeLorean]

Posted on September 08, 2014 at 17:02

Having 2048 bytes (2KB) is not going to be any good for creating a mass storage device.

The block sizes should be 512 bytes, unless you plan on learning a lot more about how this works. You should perhaps try 100 blocks, which would be 50KB, and your read/write routines are not memory/byte addressed, they are block addressed, and each block should be 512 bytes. Suggest using memcpy(). Remember you are making a BLOCK STORAGE DEVICE. I posted examples of using SDRAM on the STM32F429I-DISCO (8MB) as an MSC