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SD card proprietary modes - have these escaped into the wild?

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AFAICT the only one of the multiple SD modes which is not secret is the "SPI" serial mode, described e.g. here
It seems to be limited to about 5mbps, which is fine for writing mp3 files in say a sound recorder, but not much good for anything faster.

I did a google on whether any of the proprietary modes have been reverse engineered and documented but haven't found anything. Well, the file is called
and there are many google hits but none of them lead to a real PDF.

ST seem to have implemented it in the 32F4 but one needs proprietary software to drive it.

Have a look there:

But 4-bit mode enforces CRC, it's not optional like in SPI mode.
Not only that: Each of the 4 data lines use its own CRC, it would be a lot of processing power if done in software.

CubeMX works with 4-bit SD, you can investigate ST code and implement your own.


--- Quote from: peter-h on October 30, 2021, 07:14:47 pm ---ST seem to have implemented it in the 32F4 but one needs proprietary software to drive it.

--- End quote ---

Bullshit.  :bullshit:

//All required code is freely available even from the vendor, ST. Even the initialization command sequence for 1/4/8 bit SDIO is freely available even from the horses mouth, ( )

I have no clue what do you have a need to reverse engineer here.

OK, so it is all provided, and you just need to purchase the license from SDCARD?

I am informed that the fastest 4 bit mode is still proprietary. Is that incorrect?

Yansi - you may call it "bullshit" but what does this text mean?

Notice of SD Simplified Specifications
The following conditions apply to the release of any and all parts of the simplified specifications (‚ÄúSimplified Specifications‚ÄĚ) by the SD Card Association and the SD Group. The Simplified Specifications are a subset of the complete SD Specifications which are owned by the SD Card Association and the SD Group. These Simplified Specifications are provided on a non-confidential basis subject to the disclaimers below. Any implementation of the Simplified Specifications or any portions there of may require a license from the SD Card Association, SD Group, SD-3C, LLC or other third parties.

How do you translate "simplified" into English?

Nominal Animal:
Teensy 3.5, 3.6, and 4.1 have microSD sockets built-in using SDIO.  The relevant Teensyduino/Arduino library is SdFat, which is licensed under the MIT license.  You'll find the SDIO specifics in src/SdCard/Sdio{Card.h, Teensy.h, Teensy.cpp}.  The source for the information needed is NXP Community thread #99202, and the SDHC_K60_Baremetal.ZIP therein provided by NXP's Petr Gargulak.

As far as I know, implementing SDIO on hardware that does have the hardware support for SDIO, does not actually require access to the proprietary non-free SDIO protocol documentation.  The existing information available on the net provides enough information to implement this.

Now, whether you need an additional license, depends on whether you need to mention "SD", "SD card", associated logos, or pictograms; and your own local legal jurisdiction.  The main point of said licenses is to give you permission to use the related trademarks, logos, and possibly patents/utility patents.  As of 2021, the SD Host/Ancillary Product License Agreement is $5000 per year, but if you use a dev board, dev kit, or an MCU, you may already be covered by the manufacturer's license anyway.


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