Could the SD slot connect to the Arduino without..

Forum 2005-2010 (read only) Hardware Interfacing
1

Hello to everyone,

i have a question about the SD card slot

there are 9 pins of the SD card slot.
Could i just connect the SD card slot to the arduino without any resistors ?

Thanks a lot.

max

2

Unfortunately, no, you can't connect directly to Arduino without resistors. The logic level voltage on the SD card is 3.3 volts. The Arduino logic levels are 5 volts. I was looking into building an adapter and found one on Instructables. He talks about the voltage also. http://www.instructables.com/id/Cheap-DIY-SD-card-breadboard-socket/

3

The SD uses CMOS logic (3.3V) and most Arduino boards use 5.0V (TTL) so you'd need some kind of logic level translation for the SD/Arduino interface (and the simplest is using resistor voltage dividers), but if your Arduino runs at 3.3V, you should be able to hook up the SD interface without using any resistors.

4

i am trying to use the circuit on the above, and using the fat16write example in the fat16 library, but it told me that

Type any character to start
error: card.init
SD error: 1

what is the possible fault? i really don't know it

and it show me this

Error inside Serial.serialEvent()
java.io.IOException: Bad file descriptor in nativeavailable
      at gnu.io.RXTXPort.nativeavailable(Native Method)
      at gnu.io.RXTXPort$SerialInputStream.available(RXTXPort.java:1532)
      at processing.app.Serial.serialEvent(Serial.java:215)
      at gnu.io.RXTXPort.sendEvent(RXTXPort.java:732)
      at gnu.io.RXTXPort.eventLoop(Native Method)
      at gnu.io.RXTXPort$MonitorThread.run(RXTXPort.java:1575)

Thanks a lot, i really don't know what it is talking about.
i very appreciate it.

5

This is a common error for resistor based level shifters. Many SD cards now use edge detectors and require faster SPI rise times than the resistor level shifters provide.

Look at the readme.txt file in fat16lib for details .

Also double check your wiring/connections. About half of the time this error indicates a wiring error since it occurred on the first command to the SD card.

6

How tolerant is that 3.3 V level need for the SD card, anyway?

I mean, could you level shift by putting a couple of .7 V dropping diodes inline, giving you a voltage level approx 3.6 V? Is 3.6 V too high (8-9% diff, I think)?

Would it be any faster than a voltage divider?

7

I don't much like that this as it only has two channels when most applications need more but it's cheap.

8

The SparkFun level shifter is resistor based for 5 -> 3.3 V and won't work.

Use an IC buffer like these products.

Adafruit SD shields

SparkFun Shield:

Gravitech module http://yhst-27389313707334.stores.yahoo.net/sdcaad.html