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SD(IO) vs SPI for reading SD cards


#1

Was wondering if anyone had experience with this matter. I’m working on testing some SD card stuff, and noticed that the Netduino 3 actually has the SD card hooked up to read the SD off SPI3, not the SDIO channels. Since I’m wanting to stream audio from the SD card I do want it fast, and the 4-bit SDIO seems that it could achieve a lot faster transfer speeds. However, I"m going to be using Fat32 since I need the files to be read by the computer as well.

From what I’ve read, due to the way the SD card is organized you actually won’t get too much more performance by using SDIO since you are limited by the time reading sectors and cannot utilize the speed.

Also, it seems that SPI is a lot easier to wire as it’s only 4 wires with one pullup, vs 6 wires all with pullups on the SDIO, and space is a concern with this board.

Was just curious if anyone has experience with both and has any potential advice.


#2

@thechipguy take a look at this doc, may help to understand under the hood …
https://yannik520.github.io/sdio.html

Note: to achieve better speed transfers SDIO is the way, but you need also DMA help. ST has good demo programs for STM32F4/F7 chip reading SD & Usb MSD music MP3 play.