In USB Mass storage device class, does both side of handshaking is possible between device and host?

[PANKAJ KHARCHE]

Hi,

I am working on USB Mass Storage Device application using STM32 -F411E Discovery board . I have generated the USB Mass Storage device code using STM32 Cube Mx tool. I have created the 64Kb drive using internal RAM. The Host can write & read the data from this drive. Now my question is that, Can device also read & write the data into the same drive?

I need the both side of handshaking between device and host for my application. If is it possible then tell me the steps to write & read the data into the drive from device side?

Regards,

Pankaj

[Tesla DeLorean]

On the device you could access memory/files via FATFS.

Writing can be very problematic due to coherency issues with Windows/Linux caching, etc. Can be addressed by reporting NOT READY or MEDIA CHANGED appropriately, but complexity beyond scope of a forum response.

[PANKAJ KHARCHE]

Hi,

Thanks for the quick reply,

I am not dealing with Windows/Linux PC OS. I am testing with STM32 USB MSC Host and Device firmware, in that case i don't thing any issue should happens. What do you think? But i am getting issue when i am writing using FATFS in Device Drive, below is my code sequence to write data....

//******************************************************************************

static void MSC_Application(void)

{

 FRESULT res;           /* FatFs function common result code */

 uint32_t byteswritten, bytesread;      /* File write/read counts */

 uint8_t wtext[] = "This is STM32 working with FatFs"; /* File write buffer */

 uint8_t rtext[100];         /* File read buffer */

  

 /* Register the file system object to the FatFs module */

 if(f_mount(&USBDISKFatFs, (TCHAR const*)USBDISKPath, 0) != FR_OK)

 {

 /* FatFs Initialization Error */

 Error_Handler();

 }

 else

 {

 /* Create and Open a new text file object with write access */

 if(f_open(&MyFile, "STM32.TXT", FA_CREATE_ALWAYS | FA_WRITE) != FR_OK) 

 {

  /* 'STM32.TXT' file Open for write Error */

  Error_Handler();

 }

 else

 {

  /* Write data to the text file */

  res = f_write(&MyFile, wtext, sizeof(wtext), (void *)&byteswritten);

   

  if((byteswritten == 0) || (res != FR_OK))

  {

  /* 'STM32.TXT' file Write or EOF Error */

  Error_Handler();

  }

  else

  {

  /* Close the open text file */

  f_close(&MyFile);

   

  /* Open the text file object with read access */

  if(f_open(&MyFile, "STM32.TXT", FA_READ) != FR_OK)

  {

   /* 'STM32.TXT' file Open for read Error */

   Error_Handler();

  }

  else

  {

   /* Read data from the text file */

   res = f_read(&MyFile, rtext, sizeof(rtext), (void *)&bytesread);

    

   if((bytesread == 0) || (res != FR_OK))

   {

   /* 'STM32.TXT' file Read or EOF Error */

   Error_Handler();

   }

   else

   {

   /* Close the open text file */

   f_close(&MyFile);

    

   /* Compare read data with the expected data */

   if((bytesread != byteswritten))

   {     

    /* Read data is different from the expected data */

    Error_Handler();

   }

   else

   {

    /* Success of the demo: no error occurrence */

    BSP_LED_On(LED4);   

   }

   }

  }

  }

 }

 }

}

//*************************************************************

After USB MSD initialization i am calling MSC_Application() function to check the data can be read or write from the drive. But the code stuck after calling f_open() function.

Also i am confusing what function should i use to write data into the device drive .... STORAGE_Write_FS() ; function to write data or f_write() FATFS function as mention in above code.

Reagrds,

Pankaj