Questions re embedding MMC/SD (and digital cameras)

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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?

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?

Re: Questions re embedding MMC/SD (and digital cameras)
I can't anwser for the second part of your question but for the first part,
I did it this way on our new micro board.

I use an SD card connector with MMC interface. I have not do any testing at
this time but I will do next week.

If you want, I can confirm you when I finish testing.

Jocelyn


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

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Great, thanks for the feedback. I've got Sandisk's docs and it seemed
like this was possible, but I wasn't sure.

I'm going to ask someone with an SD-supporting camera to fill a card
with images and send it to me. I can't imagine why they would want to
use crypto, but you never know...

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

Hi:

I've read some documents from sandisk etc. The main difference i found
besides encryption is that SD is faster than MMC.

Greetings
--
Steve Sousa



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

SD can be operated in MMC mode which is fully compatible in spite of
initialization which differs slightly in one command.
I do not remember the details, if needed i must check the sources.



snipped-for-privacy@larwe.com (Lewin A.R.W. Edwards) wrote in

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Re: Questions re embedding MMC/SD (and digital cameras)
snipped-for-privacy@larwe.com (Lewin A.R.W. Edwards) wrote in message
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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.

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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.

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