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MMC Cards

MultiMediaCard is a flash standard formed by the MultiMediaCard Association (MMCA). It is an open standard that defines the physical, functional and interface specifications of MultiMediaCards (MMCs), postage-stamp size, removable memory cards used in mobile phone, digital imaging and portable consumer electronics applications.

MMC is based on a open, royalty-free standard.

Formatting MMC Cards

MMC Cards can be formated in one of two ways:

  1. Superfloppy
  2. Harddisk (including MBR, and partition table)

The below examples assumes that /dev/sdd is the MMC Card on host. It is likely to be something else - depending on your host system and distribution.

Most of the commands below done on the host are done as root - either on your host, or on the target Blackfin

Superfloppy

Superfloppy is the default format under Windows (which is the reason to understand, and test it).

Formating as superfloppy is a little more work under Linux.

  1. Clear out the first sector of the disk.
    imhotep:~ # dd if=/dev/zero of=/dev/sdd bs=512 count=1
    1+0 records in
    1+0 records out
    512 bytes (512 B) copied, 0.00209127 s, 245 kB/s
    
  2. Create the file system
    imhotep:/home/rgetz/blackfin/trunk/u-boot/u-boot-2009.03 # mkfs.msdos -I -n mmc_card -F 16 -v /dev/sdd
    mkfs.msdos 2.11 (12 Mar 2005)
    /dev/sdd has 8 heads and 61 sectors per track,
    logical sector size is 512,
    using 0xf8 media descriptor, with 494080 sectors;
    file system has 2 16-bit FATs and 8 sectors per cluster.
    FAT size is 242 sectors, and provides 61695 clusters.
    Root directory contains 512 slots.
    Volume ID is 4a3554bd, volume label mmc_card   .
    
  3. check things out
    imhotep:~ # fdisk -l /dev/sdd
    Disk /dev/sdd: 252 MB, 252968960 bytes
    8 heads, 61 sectors/track, 1012 cylinders
    Units = cylinders of 488 * 512 = 249856 bytes
    
       Device Boot      Start         End      Blocks   Id  System
    
  4. mount the disk
    imhotep:/home/rgetz/blackfin/trunk/u-boot/u-boot-2009.03 # mount -t vfat /dev/sdd /media/disk/
    imhotep:/home/rgetz/blackfin/trunk/u-boot/u-boot-2009.03 # mount
    [snip]
    /dev/sdd on /media/disk type vfat (rw)
    

With Partition table