Difference between revisions of "MultiMediaCard"

Revision as of 13:38, 29 May 2008

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 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 a DevFull you can use the MMC/SD onboard connector and an adaptor for miniSD and microSD

All needed drivers are included in standard Armadeus Linux image.

Usage

Just mount the MMC like you will do on your PC, for example (FAT32 formatted card):

# mount -t vfat /dev/mmcblk0p1 /mnt/mmc

You can then access the MMC's files from /mnt/mmc directory

The MMC driver is now included inside the Linux kernel (no more a module) but if you want to use it as a module you will have to:

# modprobe imxmmc
# modprobe mmc_block

If you encounter this message or something like that

Unable to load NLS charset cp437
FAT: codepage cp437 not found

you have to change the right charset for the current file system:

make linux-menuconfig

In Device Drivers->MMC/SD Card support->iMX Support

In FileSystems->Native Language Support you can select the right charset:

ex: NLS ISO 8859-1  (Latin 1; Western European Languages)

Booting from MMC/SD

When your rootfs is too big to be put on the APF9328 FLASH, you can always use a MMC/SD like a Hard Drive and boot from it. To do that you must have MMC drivers compiled as builtin in your Linux kernel (done by default in standard Armadeus kernel)

• Format your MMC with Ext2 filesystem:

[armadeus] $ sudo mkfs.ext2 /dev/sdxx

• Mount your MMC/SD on your Host filesystem, for example in /media/mmc

[armadeus] $ sudo mkdir -p /media/mmc
[armadeus] $ sudo mount /dev/sdxx /media/mmc

• Then put your rootfs on this MMC/SD: in Buildroot configure rootfs to be tar-ed:

[armadeus] $ make menuconfig

Target filesystem options --->

[armadeus] $ make

and then:

[armadeus] $ sudo tar xvf ./buildroot/binaries/armadeus/rootfs.arm.tar -C /media/mmc
[armadeus] $ sudo umount /media/mmc

• in U-Boot then use (with MMC/SD/microSD inserted):

BIOS> run mmcboot

• if you want to automatically boot from SD at each startup then replace default bootcmd U-Boot macro:

BIOS> setenv bootcmd run mmcboot
BIOS> saveenv

(default bootcmd is run jffsboot)

Performances

• MMC/SD#Supported_Cards

Installation (obsolete now because driver is included in default Armadeus kernel)

When you build your kernel image, then modify its configuration:

[armadeus]$ make linux-menuconfig

in Device Drivers->MMC/SD Card support->iMX Support In FileSystems, don't forget to add support for the filesystem you want to use on the MMC and if you activate FAT/VFAT, don't forget to activate Native Language Support (NLS) otherwise you'll get errors like:

Unable to load NLS charset cp437
FAT: codepage cp437 not found

Save your configuration and then rebuild your kernel image:

[armadeus]$ make linux

now you should have following drivers in your kernel source tree:

drivers/mmc/

Copy mmc_core.ko, imxmmc.ko & mmc_block.ko to your target root filessytem in /lib/modules/ or reflash the generated rootfs.

If not already existing then create the MMC block devices:

# mknod /dev/mmcblk0 b 254 0
# mknod /dev/mmcblk0p1 b 254 1

If not already existing then create the mount point (/mnt/mmc):

# mkdir -p /mnt/mmc

Links

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