MultiMediaCard

2009-08-03T14:04:26Z

BrunoLe: /* Card insertion */

Instructions to use the MultiMediaCard (MMC/SD) on your Armadeus board

==Introduction==

You can use standard MMC/SD/miniSD/microSD cards with your Armadeus board:
* with a DevLight V1, you must have [[MMC/SD | the corresponding connector attached to your development board.]] and use an adaptor for miniSD and microSD
* with a DevLight V2, you can use the onboard microSD connector
* with an [[APF9328DevFull]], you can use the MMC/SD onboard connector and an adaptor for miniSD and microSD
* with an [[APF27Dev]], you can use the onboard microSD connector

All needed drivers are included in the standard Armadeus Linux image.

==Card insertion==
You should something like that on the Linux console:
<pre class="apf">
# imx-mmc imx-mmc.0: card inserted
mmc0: host does not support reading read-only switch. assuming write-enable.
mmc0: new SD card at address 01b0
mmcblk0: mmc0:01b0 SD512 500224KiB
mmcblk0: p1
</pre>

Note :
If the special files /dev/mmcblk0, /dev/mmcblk0p1 /dev/mmcblk0p2 ... /dev/mmcblk0p7 are NOT present on your filesystem,
create them by hand :
# mknod /dev/mmcblk0 b 179 0
# mknod /dev/mmcblk0p1 b 179 1
# mknod /dev/mmcblk0p2 b 179 2
...
# mknod /dev/mmcblk0p7 b 179 7

(It happened to me after upgrading an APF9328+DevLight from version 2.3 to 3.1)

==Mounting the MMC/SD==

* Just mount the MMC like you will do on your PC, for example (FAT32 formatted card):
<pre class="apf">
# mount -t vfat /dev/mmcblk0p1 /mnt/mmc
</pre>
* Then, you can access the MMC's files from the ''/mnt/mmc'' directory

If you have problems with vfat code page [http://www.armadeus.com/wiki/index.php?title=MultiMediaCard#VFAT_Code_Page click here]

==Booting from MMC/SD==
When your rootfs is too big to be put on the APF Flash, you can always use a MMC/SD like a Hard Drive and boot from it (this is possible because standard Armadeus kernel is compiled with the MMC driver built in).

===Prepare your card===
* On your APF board (to avoid to crash your Host HD), create a good partition table:
<pre class="apf">
# /sbin/fdisk /dev/mmcblk0
Delete all existing partion with 'd'
Create a primary partion: 'n' then 'p' then '1'
Change bootflag to Linux: 't' then '83'
Save partition table: 'w'
(To quit without saving: 'm')
</pre>
* Then, on your PC, format your MMC with Ext2 filesystem (booting on FAT is bad :-) ):
<pre class="host">
$ sudo mkfs.ext2 /dev/sdX1 (replace X with your MMC reader drive letter, if your Laptop has an integrated
MMC reader then use mmcblk0p1 instead of sdX1)
</pre>
* If not automatically detected/mounted by your distribution, mount your MMC/SD on your Host filesystem (for example in ''/media/mmc''):
<pre class="host">
$ sudo mkdir -p /media/mmc
$ sudo mount /dev/sdX1 /media/mmc (replace X with your MMC reader drive letter, if your Laptop has an integrated
MMC reader then use mmcblk0p1 instead of sdX1)
</pre>

===Put your rootfs on the MMC/SD===
* Buildroot should be configured to generate a tar-ed rootfs '''(now done by default)'''.
[armadeus] $ make menuconfig
<pre class="config">
Target filesystem options --->
</pre>
[[Image:Menuconfig_tar_rootfs.png]]
<pre class="host">
[armadeus] $ make
</pre>
* and then uncompress the rootfs to the SD card:
<pre class="host">
$ make shell_env
$ source armadeus_env.sh
$ sudo tar xvf $ARMADEUS_ROOTFS_TAR -C /media/mmc
$ sudo umount /media/mmc
</pre>

===Boot===
* Insert the MMC/SD/microSD in the corresponding slot of your Armadeus board and then under U-Boot do:
<pre class="apf">
BIOS> run mmcboot
</pre>
* if you want to automatically boot from SD at each startup, modify the ''bootcmd'' U-Boot macro:
<pre class="apf">
BIOS> setenv bootcmd run mmcboot
BIOS> saveenv
</pre>
(default bootcmd when you receive your board is ''run jffsboot'' = boot from FLASH)

==Performances==
* [[MMC/SD#Supported_Cards| Show tested cards performances]]

==Troubleshots==
===VFAT Code Page===
If you encounter this message (or something similar):
Unable to load NLS charset cp437
FAT: codepage cp437 not found
you have to add the charset to the supported kernel ones:
$ make linux26-menuconfig
<pre class="config">
File systems --->
-*- Native language support --->
<*> Codepage 437 (United States, Canada)
...
<*> NLS ISO 8859-1 (Latin 1; Western European Languages)
...
</pre>

==Links==

* http://en.wikipedia.org/wiki/MultiMedia_Card

{{LanguageBar|MultiMediaCard|MultiMediaCard|MultiMediaCard}}

[[Category:MassStorage]]

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MultiMediaCard