The amazing world of SD cards

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The amazing world of SD cards

Postby jonnection » Thu Jun 11, 2015 11:15 am

[geek]
I've been debugging SD cards and SDHC cards because I was trying to make a Gamebuino loader that works with SDHC cards. So far I haven't had success, it seems very difficult (impossible ?) to get a SDHC compatible bootloader to fit in 2K.

In the process I have been digging deep into the SD card format and looking at communication between the Gamebuino MCU (the atmega328) and the SD card.

Now clement had tested my Operation Fox game and was reporting that the game was laggy to the point of unplayable - where as I have had no problems at all. The only difference that I can think of is that I use different SD cards. I am amazed that such differences come to surface.

Also, I have really been wondering why the loader / bootloaders work on Rodot's SD cards, but us builders of Fakebuinos have constant problems in getting them to work reliably.

We tend to think that SD cards are similar with each other, but it is not so:
the modest looking micro SD card may be of standard size of plastic, but on the inside it is actually an amazing and a very complicated device.

Did you know, for example that with high probability, your micro SD card has an embedded ARM7 class microcontroller that runs at 100 Mhz and is way more powerful than the atmega328 of the Gamebuino ? This microcontroller performs extremely quick error correction, wear-levelling and other tasks.

Did you know, that a big chunk of your micro SD card memory is bad (even up to 80 %), and the microcontroller uses highly dedicated bad sector management and probabilistic error correction to use the flash memory at all ?

I sure didn't know that.

Very interesting talk on the topic:


[/geek]
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Re: The amazing world of SD cards

Postby rodot » Sun Jun 14, 2015 9:53 am

Thanks for sharing, very interesting indeed! :)
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Re: The amazing world of SD cards

Postby Wafflez » Tue Oct 27, 2015 11:30 pm

Deep stuff, man.
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