MMC/SD

ahbaba67 · Joined: 09 Apr 2006 Posts: 7

My thesis is a mobil meteorology station. I need to writing a data in MMC or SD card. Can you help me this problem. But I can write a data in text file(.txt or .dat) form in MMC or SD card.

Note: I use a PIC16F877A.

Thanks a lot.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Just go over to the Code Library forum and look for MMC code that's
posted there. There's a entry for a FAT file system for MMC.
Here's a link to the forum:
http://www.ccsinfo.com/forum/viewforum.php?f=2

ahbaba67 · Joined: 09 Apr 2006 Posts: 7

Do you know another MMC/SD card circuits and programs.

Thank you

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

The PIC16F877A is a bad choice to use as a processor in combination with an MMC card because of the small memory of this processor. Writing data to an MMC card can only be done in blocks of 512 bytes which is a problem with the 384 bytes of RAM in the PIC16F877A. Some people have found workarounds for the memory limitation by first storing the data in an external memory like FRAM but this will make your design more expensive, more complex and not compatible to standard available driver software.

Reading data from the MMC (MP3 players, etc.) is no problem as this can be done in block sizes from 1 byte upwards.

Save yourself a lot of problems and use a processor with more RAM memory, preferably 1k byte or more.

ahbaba67 · Joined: 09 Apr 2006 Posts: 7

then which do you choose a Pic in your project. Can you help me?

asmallri · Joined: 12 Aug 2004 Posts: 1634 Location: Perth, Australia

I suggest you look at the PIC18F4620. It is electrically pin compatible with the PIC16F877 so no hardware changes are required. I use the PIC18F2620 (28 pin version of the PIC18F4620) but also use a FRAM because I require high speed buffering of incoming data and the need to maintain multiple open files concurrently.
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Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!

SLo · Guest

Be careful with the electrically pin compatible statement, there are some differences such as the available A to D pin combinations and the removal of the open drain output pin. Generally Microchip are good at making devices pinout interchangable, but it always pays to compare the datasheets.

Steve.