Questions re embedding MMC/SD (and digital cameras)

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?

Reply to
Lewin A.R.W. Edwards
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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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Reply to
Jocelyn

Hi Jocelyn,

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...

Reply to
Lewin A.R.W. Edwards

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
Reply to
Steve Sousa

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.

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Reply to
Manuel Abrecht

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.

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.

Reply to
Scott Bissett

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