SD/MMC Mini Board - the basics

Hi,

Has anyone used the Futurlec SD/MMC Mini Board http://www.futurlec.com/Mini_SC.shtml with an Arduino...? Could I ask how you wired the two together and which library you used to read/write to the card?

The pins available are:

  • 3.3V
  • CD
  • DAT2
  • CD/DAT3
  • CMD
  • CLK
  • DAT0
  • DAT1
  • WP
  • GND

Sorry - very basic question - thanks.

Yes, I used it with a 3.3v CortexM3. For 5v Arduino you need to drop the voltages of the 3 input lines, sclk, datain, cs. DataOut is fine. Wire this device up to the SPI port. i.e. you need to connect: Vcc, Gnd, Sclk, MISO, MOSI, CS of the arduino SPI to the card. Also I don't think you need the pullups enabled either (arduino internals are set).

Heres the pin mapping : http://www.interfacebus.com/Secure_Digital_Card_Pinout.html

Pins8-9 are NC.

Heres a short article on dropping the voltage from 5 to 3.3: http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=65

I used SDuFat library to start but its very limited and quite painful(empty file of desired size has to pre-exist on card, etc).

I then found Fat16 library. Its bigger, but easier to use, lets you open files from scratch, etc. More like a normal file lib. However, this lib does not like resistor voltage dividers, theres a note about setting the spi bus speed lower. I backed up and ordered a few 74HC4050N line buffer chips, and these work great. Instructions on using a line buffer are in Fat16 help files.

Good luck.

BTW, the best SD/MMC board I've found for 5V systems is from Gravitech: http://yhst-27389313707334.stores.yahoo.net/micaad.html

On-board 3.3 regulator and a "real" level shifter (74LCx245). Real easy to use.

Thanks for the replies folks, I will give it a whirl.... much appreciated... I didn't even know about the volatge issue !!