Difference between revisions of "MultiMediaCard"

Revision as of 23:01, 2 March 2009

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 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:

# 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

Mounting the MMC/SD

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

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

• Then, you can access the MMC's files from the /mnt/mmc directory

If you have problems with vfat code page click here

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)

Prepare your card

• On your APF board (to avoid to crash your Host HD), create a good partition table:

# /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')

• Then, on your PC, format your MMC with Ext2 filesystem (booting on FAT is bad :-) ):

[armadeus] $ 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)

• Mount your MMC/SD on your Host filesystem (for example in /media/mmc):

[armadeus] $ sudo mkdir -p /media/mmc
[armadeus] $ 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)

Put it your rootfs

• Then put your rootfs on this MMC/SD: in Buildroot configure rootfs to be tar-ed (should be done by default).

[armadeus] $ make menuconfig

Target filesystem options --->

[armadeus] $ make

• and then uncompress the rootfs to the SD card:

[armadeus] $ sudo tar xvf ./buildroot/binaries/apf9328/apf9328-rootfs.arm.tar -C /media/mmc
[armadeus] $ sudo umount /media/mmc

Boot

• insert the MMC/SD/microSD on your Armadeus board and then in U-Boot use:

BIOS> run mmcboot

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

BIOS> setenv bootcmd run mmcboot
BIOS> saveenv

(default bootcmd is run jffsboot)

Performances

• MMC/SD#Supported_Cards

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

In File systems ---> -*- Native language support ---> you can select the right charset:

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

Installation (now obsolete because MMC driver is statically built in default Armadeus kernel)

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

[armadeus]$ make linux26-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 linux26

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

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

Links

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