read/write on mmc card with PIC18fxx problems!!!help me plz

farhani123 · Joined: 26 Apr 2011 Posts: 3 Location: Tunisia

Dear all,
I need very urgently to find out how to read and write on a mmc card memory. I'm running out of time and i need this to complete my project to take my engineering diploma, so can anyone please help me to get out from this problem. I'm really stuck.
I use ccs c compiler.
I find out that I should use the spi protocol. I tried to use some function such as "spi_write(value) " and "spi_read(value)", predefined on the ccs c compiler but I failed to make any results:(((

Help will be greatly appreciated.

Thank you

Ttelmah · Joined: 11 Mar 2010 Posts: 19506

Several things you need to start with:
What voltage is your PIC?. If you are using a 5v PIC device, you _need_ a 3.3v to 5v converter device between the MMC card and the PIC. Resistor divider in the other direction. This needs to be sorted out _before_ you start to talk to the card....
Then, do you want to store the data as if the mmc card is just a memory device, or do you want to use it as a file system?. If the former, you need to look at mmc_spi.c. Understand that the card needs to be talked to in 512byte blocks. This handles this for you. To talk to a file system, you then need to look at fat.c. More complex.

Best Wishes

farhani123 · Joined: 26 Apr 2011 Posts: 3 Location: Tunisia

Thanks a lot T for this clarification:)
But if you don't mind i can't honestly make difference between "file system" and "memory device" but what I'm "dreaming" to do is that i want to read data from the rs232 port and save it in the mmc card. The first part i did it but I'm stuck in the mmc part. From other side i wish that i can find data that i stuck in the mmc card in a .txt file but i think it is too difficult to reach, isn't it??

farhani123 · Joined: 26 Apr 2011 Posts: 3 Location: Tunisia

I found the "mmc_spi" and the "mmcsd" drivers and I had tried to use functions such as "mmc_write_block(address, size, *ptr)" and "mmc_read_block(address, size, *ptr)".
I made: address=0x00,size=512 and ptr="hello", in order to write "hello" in the block of 512byte wich start from the address 0x00.
The problem is when I simulate this in Proteus isis and i use the spi debugger, I see strange code that the PIC18f4520 send to the mmc card("ff ff ff ff ff ff ff ff") which have nothing to do with the word I wish to send to the mmc. In addition, I found nothing on the mmc card when I read it with the function previously declared!!!!!
Have you, please, T any idea what is wrong with this??
Thanks in advance:)

Sergeant82d · Joined: 01 Nov 2009 Posts: 55 Location: Central Oklahoma

Why not just use the example code and drivers which are included with the compiler?

in the /examples folder, ex_fat.c
and it includes two files from the /driver folder, fat.c & mmcsd.c

I am in the process of implementing an SD card into my project, and using these files it has been pretty easy to get it up and running.

Rod_O · Joined: 23 Sep 2011 Posts: 4

temtronic · Posted: Mon Sep 26, 2011 1:17 pm

Also be aware that Proteus is FULL of bugs,errors, faulty logic, bad DRCs, etc. You're better off working with real hardware and using the examples CCS supplies!

AND

be sure to use the LF version of the PIC(low voltage) OR logic level translator chips btweeen the PIC and the MMC card !

asmboy · Joined: 20 Nov 2007 Posts: 2128 Location: albany ny

Are you locked in to this idea and not other for your project????

Confession - i have had a need for exactly or almost what you want to program yourself -- but buy it off the shelf for $25 all ready to go -
ie: capture text on a MICRO SD card up to 16GB in size.
see:

http://www.sparkfun.com/products/9530

NOTE: current delivery firmware in the product is HUGELY improved and SO EZ to use now that it is just about idiot proof too.

I use it to protect high value instrument capture data from other PIC controllers - in an automated instrument environment -as a backstop against a HOST PC crash while expensive, impossible to reproduce data is being delivered.

i think perhaps the "openlog" module is exactly what you are trying to design.

Rod_O · Joined: 23 Sep 2011 Posts: 4

I did it :D
I use Suky's library (SDCard_Hard.c)... Now I can read and write directly to SD cards in Proteus (I save the SD card image in a .mmc file, from where i can see - with winhex or notepad - the changes in the sd image file. Now i have to see if it works with big (>2GB) SD Cards.
And then maybe FAT system... but i dont need it right now.
Thanks everyone XD
...
Rod_O
_________________
>Rod_O