Beaglebone: Add 2. SD Card

Hi

is there a simple way to add a second SD card to BeagleBone without using the USB port?

Regards

Peter

MMC1 is conencted to the expansion header. You should be able to wire a conenctor into it via a Cape protoyping board. Make sure you add the capacitors and the pullup resistors.

Gerald

Gerald,

Thanks very much for your answer.

Well, I have found the MMC1 but did not think that this easy to use it. Will the kernel detect the second SD automatically or have I to change settings or so?

Regards

Peter

The Kernel will need some help! It currently does not look for it. As it is connected on the expansion header, that would fall under the Cape area, requiring a EEPROM as well. But it should be possible to change the kernel to access it, depending on how you choose to implement it.

Gerald

What would it take for the kernel to recognize and use an SD card connected via SPI rather than MMC. would that be much more difficult?

Eric

The kernel driver starts with one bit data to scan the SD card. So, I guess MMC_CMD, MMC_CLK, MMC_DAT0 plus one GPIO for CARD_INSERT will be the minimum requirement. If you need Write-Protect, you need another GPIO. After the hand-shaking, the kernel driver will figure out that the SD card can be accessed with one bit serial data mode.

Eric

Hi Eric

will this work with BeagleBone (without a EEPROM on a cape) as well?

Peter

Gerald,

thanks a lot for your reply.

So is an EEPROM mandatory if you connect something to the expansion header?

Peter

I do not have a Beaglebone. However, I have designed a MMC daughter card for the Beagleboard. I also modified the beagleboard specific source code to enable the 2nd mmc slot. I remember I did not modify the mmc driver source code though I added printk to print debug message to stdout. So, technically, you do not need the EEPROM.

-Eric

EEPROM is required if you plan to sell the board as a Cape. If this is just for your use, then it is not required.

Gerald

Eric,

thanks for this information.

Where did you do the changes?

Peter

Eric,

thanks a lot.

Peter

It is in the file “arm/mach-omap2/board-omap3beagle.c”. You look for mmc and learn how to create the 2nd mmc.

-Eric

It is in the file "arm/mach-omap2/board-omap3beagle.c". You look for mmc
and learn how to create the 2nd mmc.

As a reference, You can also refer to the file arch/arm/mach-omap2/board-am3517evm.c; where 2 mmc instances are already created.

Search for "omap2_hsmmc_info".

Thanks,
Vaibhav

Hi Vaibhav and Eric,

thanks a lot for your replies. This will help.

Peter