On May 17, 2006, at 9:55 AM, Harold Mills wrote:

I'm considering using gumstix for a project that would need as much storage as possible, and have some questions about MMC/SD/CF cards that I hope people can answer.

1. Will SD cards fit physically into the MMC slots on the Basix and netMMC boards? I've read (see, for example,  http://en.wikipedia.org/wiki/Secure_Digital) that SD cards are slightly thicker than MMC cards and won't fit into MMC slots. However, I see some messages in the archives of this mailing list that suggest that some people are using SD cards with gumstix. Do some SD cards fit but not others?

The gumstix slots are SD slots.  Both SD and MMC cards will fit in there.  Actually, physically there's SDIO slots, but there is no open-source SDIO driver.

2. Is there a driver available for SD cards?

Yup, it's in the linux distro which is on the 'stix.

3. Are there size limitations for MMC/SD cards that can be used with the Basix boards? David Farrell's message of December 24 of last year suggested that only cards of up to 1 GB can be used with gumstix due to a PXA255 limitation.

The upshot from the arm-linux mailing list thread which David points to is that the PXA255 MMC controller can apparently not write 1024-byte blocks, which the 2GB cards (at least the ones described in that thread) seem to require.  The cards do support 512-byte reads, so in theory you could read from those 2GB cards on a PXA255, but not write to them.

1GB cards (at least the ones people have seen so far) seem to use 512-byte blocks, and so should work just fine.  There could well be some 1024-byte block 1GB cards out there I imagine.

4. Are there size limitations for CF cards that can be used with netCF and cfstix?

None that I know of; CF basically just provides a bus to carry IDE-type stuff over, so the limits would be those of the linux IDE system, which are higher than you're likely to encouter.

C