next topic »

[on:]

Wondering if anyone has used the Parallax 32312 micro-sd card adapter on an Arduino.

If so, could you provide some guidance?
- How to get from +5v out on the UNO down to the 3.3VDC the reader requires
- Any code sample to write to/read from the card

Thanks much!

Rob

[Reply #1 on:]

Got a link?
Once past the voltage level issue, the sdfat16 library should work for you.

Look at the adafruit datalogger shield, use the same chip for level conversion.
The 3.3V regulator on the Uno may provide enough current to drive a uSD chip.

[Reply #2 on:]

Thanks for the reply.

Here's a link to the adapter: http://www.parallax.com/tabid/768/ProductID/597/Default.aspx

I bought the adapter before I bought the Uno, otherwise I'd probably have gone with the shield you mentioned.

Thanks again and Happy New Year!

[Reply #3 on:]

Okay, thats a socket and unknown value pullup resistors to 3.3V.
You need to get a 74AHC125, power it from 3.3V, power the card from 3.3V, and buffer the SCK, MOSI, and SS lines going to the socket.

MISO back to the ATMega does not need buffering.

[Reply #4 on:]

I appreciate the help, and don't mean to ask too many Q's, but I'm not sure what a 74AHC125 is as I'm fairly new to microcontrollers/electronics.

However, since it requires 3.3v, I believe I can power it from the UNO's 3.3v power socket, which I didn't see prior to my OP. But if both the 74AHC125 and card adapter need 3.3v, and the UNO only has one 3.3v out, is there a shield that will provide me with two or more so I can power both? Or, is that what the 74AHC125 is? I did a search but came up with a few different electronic components.

[Reply #5 on:]

http://search.digikey.com/us/en/products/SN74AHC125N/296-4531-5-ND/375724

http://www.ladyada.net/make/logshield/design.html
Look at how IC3A,B,C,D is wired up.

Mount your adapter, the chip, and a 100nF (0.1uF) capacitor across the power & ground pins, on a little piece of perf board.

The  Uno's 3.3V & GND gets connected to both parts.
You wil also need to connect D13 (SCK), D12 (MISO), D11 (MOSI) and D10 (SS) from the Uno to the same named pins on your card.
MISO might be DataOut, and MOSI might be DataIn.

[Reply #6 on:]

Great info!