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RTX USB MSC with MMC interface of FlashFS

Oliver Purschke

This is a general question:

Has anybody successfully implemented the RTX USB MSC together with the MMC interface of FlashFS on an LPC2148 having a microSD card connected to SPI1 ?

I used \Keil\ARM\Boards\Keil\MCB2300\RL\USB_FlashFS\SD_File as a starting point.

SPI data rates are 400 kBit/s and 15 MBit/s (LPC2148 operated @60 MHz).

MicroSD card access via FlashFS itself works fine. Also USB MSC enumerates correctly (windows recognizes the device and shows it as drive).

But accessing the drive in Windows leads to erroneous behavior varying from XP to 7.

Are there general performance issues with the above architecture?

I would realy appreciate some hints from the USB / RTX Guru ...

Thank you very much in advance.

Oliver

Parents
  • 0 in reply to Oliver Purschke

    I don't use this code, but with quick look on the source,

    1) USB host queries the capacity of the drive using ReadCapacity (or ReadFormatCapacity) SCSI command. This firmware processes this query in MSC_ReadCapacity or MSC_ReadFormatCapacity() (mscuser.c). In these routines, MSC_BlockCount variable holds the total number of blocks (sectors).

    2) MSC_BlockCount is set up in the main loop of main() (memory.c)
    MSC_BlockCount = mmcfg.blocknr;

    3) mmcfg.blocknr is read out from CSD registar of the SD card, as follows.

    MCI_23xx.c

BOOL mci_read_config (MMCFG *cfg) {
  ...
  ...
  /* Total Number of blocks */
  switch ((rval[0] >> 30) & 3) {        /* Bits 126..127      */
    case 0:                             /* SD card,  CSD v1.0 */
    case 2:                             /* MMC card, CSD v1.2 */
      v = ((rval[1] << 2) | (rval[2] >> 30)) & 0x0FFF;
      m =  (rval[2] >> 15) & 0x07;
      cfg->blocknr = (v + 1) << (m + 2);      // <------------
      break;
    case 1:                             /* SD card,  CSD v2.0 */
      v = ((rval[1] << 16) | (rval[2] >> 16)) & 0xFFFF;
      cfg->blocknr = (v + 1) << 10;           // <------------
      break;
    default:
      return (__FALSE);
  }

    Using debugger, trace the values of MSC_BlockCount and mmcfg.blocknr

    As of CSD register, refer this chapter of the SD card spec
    www.sdcard.org/.../
    5.3.3 CSD Register (CSD Version 2.0)

    Tsuneo

Reply
  • 0 in reply to Oliver Purschke

    I don't use this code, but with quick look on the source,

    1) USB host queries the capacity of the drive using ReadCapacity (or ReadFormatCapacity) SCSI command. This firmware processes this query in MSC_ReadCapacity or MSC_ReadFormatCapacity() (mscuser.c). In these routines, MSC_BlockCount variable holds the total number of blocks (sectors).

    2) MSC_BlockCount is set up in the main loop of main() (memory.c)
    MSC_BlockCount = mmcfg.blocknr;

    3) mmcfg.blocknr is read out from CSD registar of the SD card, as follows.

    MCI_23xx.c

BOOL mci_read_config (MMCFG *cfg) {
  ...
  ...
  /* Total Number of blocks */
  switch ((rval[0] >> 30) & 3) {        /* Bits 126..127      */
    case 0:                             /* SD card,  CSD v1.0 */
    case 2:                             /* MMC card, CSD v1.2 */
      v = ((rval[1] << 2) | (rval[2] >> 30)) & 0x0FFF;
      m =  (rval[2] >> 15) & 0x07;
      cfg->blocknr = (v + 1) << (m + 2);      // <------------
      break;
    case 1:                             /* SD card,  CSD v2.0 */
      v = ((rval[1] << 16) | (rval[2] >> 16)) & 0xFFFF;
      cfg->blocknr = (v + 1) << 10;           // <------------
      break;
    default:
      return (__FALSE);
  }

    Using debugger, trace the values of MSC_BlockCount and mmcfg.blocknr

    As of CSD register, refer this chapter of the SD card spec
    www.sdcard.org/.../
    5.3.3 CSD Register (CSD Version 2.0)

    Tsuneo

Children
  • 0 in reply to Chinzei Tsuneo

    The setup of MSC_BlockCount in the Keil example is based on a fixed block size of 512.

    This appears to be correct for SD cards up to 1GB.

    As stated in the SD card spec, particularly for a 2GB card, the value returned in mmcfg.blocknr can be related to other block sizes as reported by mmcfg.read_blen .

    Since the mmc_init() sets the block size actually used to 512 bytes, MSC-BlockCount has to be calculated as shown in my example:

    void checkMicroSdCard(void)
{
  MMCFG mmcfg;
  if (mmc_init())
  {
    mmc_read_config(&mmcfg);
    MSC_BlockCount = mmcfg.blocknr * ( mmcfg.read_blen >> 9 );
    ...
  }
}

    Now the correct capacity is shown in the Windows format dialog.