SD carding with SX

Lord Steve

Has anyone worked with SD or MMC cards?· SD and MMC cards don't tolerate +5 volts.· Is there a DIP package IC that does 5-to-3 volts interfacing?· I want to be able to debug this but the SX·Tech board has 5V of course.· The alternative is to breadboard it and move the SX to the board after every programming and also set up debug output blah blah.· What to do...?
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Jon Williams

I haven't, but I'm interested for a few projects.· Here's a PIC-based project I found that I'm using as a guide to get started.

http://www.captain.at/electronics/pic-mmc/

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Jon Williams
Applications Engineer, Parallax

Stephen

Here's all the files that were used to create a MMC demo some time ago... Schematics and board files are for Eagle. The SX code is for SX52. I saw it working, playing back some audio from a MMC. Pretty cool!

Cheers,
Stephen

David B

I did get a minimal card logger working a while ago, but I quit after the card developed errors; possibly from my incorrectly using it as a learning device.

But it did in fact successfully log about a half-hour of GPS data of about 80 bytes per second.

My project used discrete transistor circuits to shift 5v to 3v and used a Schmidt TTL to convert 3v out to 5v.

The program is able to distinguish between SD and MMC cards, determine the memory size of the card and write data to sectors. I used a separate Windows program to read the data from the card., so this version does not read the card.

I stopped working on this after the card read errors showed up; static RAM was for my purposes, a better match, so I continued developing my data logger in that direction.

David