[En-Nut-Discussion] FAT filesystem and SD/MMC cards

[Harald Kipp]

Hello Arnfinn,

Bad news. There is a simple FS for serial dataflash chips
http://www.ethernut.de/en/projects.html
contributed by Dusan Ferbas. It doesn't take care of wear out and
the code is a bit old. No idea if it will still work with the
latest Nut/OS.

PNUT is optimized (better say simplified) for RAM. It may be
too difficult to make it work on Flash Cards.

As far as I understood, MMC/SD Cards contain a patented algorithm
to avoid flash wear out, even if the FAT is written to the same
block over and over again. Anyone with more insight?

In general I'd prefer a journaling FS, because it would be useful
for all kind of flash memory, not just patented FAT. My interest
in the area is enormous, but the required effort...well.

The ecos JFFS2 doesn't look bad. Unfortunately it's GPL'ed and
won't fit to Ethernut's BSD licence.

Harald

At 16:40 23.06.2005 +0200, you wrote:
>Hello!
>
>I'm trying to find out how I can read and write files to a SD/MMC card 
>using a newly acquired Ethernut 2.1b.
>
>I have made a mount for a SD/MMC card reader, a voltage divider for the 
>output from the microcontroller, and connected it to the SPI bus. I have 
>downloaded the "nutmmc" example from http://usbdip.de/en/nutmmc/ and it 
>seems to run without problems on the hardware.
>
>Now, I noticed that it is not possible to write files with the FAT code 
>that I have found, and I wonder if there has been some development here 
>lately. Is there somebody I can ask for some help if I have to write the 
>functions myself? You can have whatever code I manage to come up with, if 
>it would be of any interest. :)
>
>Is there perhaps an alternative to the FAT file system when it comes to 
>reading and writing the memory card? I noticed something called PNUT; is 
>it usable for this kind of application? I don't need to read or write to 
>the card from any other device than the Ethernut card, so I just need 
>(wish for) an easy and simple way to handle files really...
>
>Any help is appreciated!
>
>Cheers,
>Arnfinn Aas Eielsen