Re: Questions re embedding MMC/SD (and digital cameras)

[EMAIL PROTECTED] (Lewin A.R.W. Edwards) wrote in message news:<[EMAIL PROTECTED]>...
> Hi all,
> 
> Quick question: I am only briefly familiar with MMC and SD, but my
> understanding is that SD is a superset of MMC, and it is possible to
> use SD cards as unprotected MMC devices without needing to acquire the
> full SD spec. Is this true? So, can I use an SD card connector, only
> use the MMC pins of it, and successfully read/write unencrypted
> content on the device?

Yes. That's exactly what I'm doing on a project I'm wrapping up right
now. Our hardware uses a SD connector (the connector has a card detect
switch, and it senses the SD's write protect switch too), and I can
read/write MMC and SD cards in SPI mode.

> Related question: Do digital cameras, in general, use the SD
> protection features, or can I read camera-formatted cards using the
> MMC-only interface above?

I wish I could answer your question.  On my project, I could only read
the contents of cards that I formatted in my embedded project. We
couldn't read from cards directly out of the package, or when
formatted as "FAT" (not FAT32) in Windows XP.  I wish I had more time
to investigate the problem.  I am using the uC/FS filesystem from
Micrium to access the cards.  It took me quite awhile to finally be
able to read from or write to the card, but it was not the fault of
the uC/FS code, which is well-written and highly portable C code.

- Scott B.