File system on STR7 using SPI

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Posted on September 29, 2005 at 20:02

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tech9Author

Associate III

Posted on September 12, 2005 at 18:14

I wonder if some code is available to build a file system on my STR7. I plan to use it on a SD card, driven by the SPI bus.

I know that connecting the SD card to the SPI bus is pretty straightforward, but I am puzzled when it comes to the FS...

Anyone has seen some software to build the FS?

Any suggestion is welcome.

Regards,

Tech

nopti_albe

Associate II

Posted on September 13, 2005 at 11:04

doesn't the sd card use 4 data pins? as far as i know only mmc is really 1 data pin serial =spi. I'm looking at this kind of things too... but there seems to be quite a lot of work ;)

tech9Author

Associate III

Posted on September 13, 2005 at 13:12

The SD card uses a data IN wire, a data OUT, a clock, and a chip select.

Looking carefully at the SPI, you get Master In Slave OUT (MISO), Master Out Slave IN, (MOSI), SCLK, and /SS. (slave select)

This fits perfectly with the previously enumerated signals.

MISO: IN, MOSI: OUT, clock: SCLK, and CS: /SS

The only remaining detail, and the biggest hurdle, is the File System. Where do I get that?

This is the main issue here: we should be able to get some sample code of how to proceed with the FS, but where?

I believe this could help a lot of people working with the STR7...

Regards,

Tech

nopti_albe

Associate II

Posted on September 25, 2005 at 11:10

http://www.sandisk.com/pdf/oem/SD_SDIO_specsv1.pdf

as you can see the transfer is using 4 bits. mmc is with 1 bit interface. maybe sd works with one bit too. You would first see how you make it work with sd, filesystem is a later development problem. there are a lot of pieces of code, but it won't be easy. it's not a 2 day job.

ben2

Associate III

Posted on September 26, 2005 at 04:52

the SD cards can be put into an SPI mode. I know this as a colleague has connected an SD card to the SPI bus. Cant help for the file system though as the SD card was memory addressed.