Hi JD123,

I am also trying to use a MMC card as a large data store that MUST be PC readable. I bought some development hardware from Ron Diol at Compsys a year back but the project got pushed aside by the urgent driving out the important. Ron was very helpful and there are some good links there.

http://www.compsys1.com/workbench/On...c_project.html

http://elm-chan.org/docs/mmc/mmc_e.html


I am thinking along the lines of preformatting the SD/MMC card in FAT 16 or 32 and loading two files of known names on the card. The SPI mode does not require any CRC calculations (I think) and is plenty fast enough for my needs.

The PIC code would open one file and append the latest data. It would close that file and open the second file, write the same code a second time and close. The two file are so if the card is removed while a file is still open, the data should be recoverable from the other file. No doubt there are better ways.

I want to keep the PIC side code as lean as possible and I can always preformat the cards but the final data must be directly readable by a PC.


Please keep this going in any forum as I think it will be a pretty interesting thread as you get it all going.

Cheers
BrianT