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Is it possible to implement SD mode on Mbed for better SD card reading performance?

Topic last updated 05 Oct 2012, by Kevin Braun. 3 replies
chaoran zhang
05 Oct 2012

I'm a beginner in Mbed. Right now I have a SD card connected with Mbed via SPI mode. The micro controller works very is slow when I load USBMSD_SD program and try to make it as a mass storage device through USB. So I guess it's probably due to the low performance of SPI. My question is, if SD mode is 4 times faster, why there is no one using it on micro controllers?

Lexington B.C.
05 Oct 2012

I belive that the 4 bit mode is propriatry,

which means it is not open source :(

I have never seen a non - OS (unix, win C?E etc with it)

do not know about other platforms, arduino ??

Cheers

Lex.

chaoran zhang
05 Oct 2012

Lexington B.C. wrote:

I belive that the 4 bit mode is propriatry,

which means it is not open source :(

I have never seen a non - OS (unix, win C?E etc with it)

do not know about other platforms, arduino ??

Cheers

Lex.

Thanks Lex, I just did some research this morning and find out only SPI is free to use.SD 4 bit mode requires license from SD association. But company like Sandisk posted their specs(very detail on SPI, not sure about SD mode) on website, can I just follow it to build a SD 4 bit mode for myself use?

Kevin Braun
05 Oct 2012

The problem is that most microcontrollers cannot support 4 bit mode in h/w. You would have to bit-bang a 4 bit mode SPI controller which in the end, would probably be much slower that what mbed can supply today.

...kevin