What pins does the ethernet shield really use? According to the schematic...
D2 - Ethernet interrupt (optional with solder bridge "INT")
D4 - SD SPI CS
D10 - Ethernet SPI CS
D11 - Not connected (but should be SPI MOSI)
D12 - Not connected (but should be SPI MISO)
D13 - SPI SCK
A0 - SD Write Protect
A1 - SD Detect
So can I use A0 and A1 even though they appear to be connected to the SD card?
Is there a better resource to see what pins shields are using?
Sorry, I was talking about the ethernet shield from the arduino team http://arduino.cc/en/Main/ArduinoEthernetShield
And by better I meant a matrix that you could see shields along the left and pins along the top and see which pins are used by which shields.
there may be only ONE "Arduino Ethernet Shield" board
There are at least 3 that I know of using the Wiznet chip: Adafruit and NKC have their own variants of the "official" design. I have two of the Adafruit boards, and am happy with them.
I've also seen at least one shield for the Microchip Ethernet chip (ENC28J60??), and I'm pretty sure I've seen mention of others.
So it's really important to identify which shield you're using when asking questions.
I made a start on such a list a couple of weeks ago, see this thread
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1285946134/3#3
or for direct links to the table
www.robgray.com/temp/Arduino-shield-pins-used.xls
If you don't trust an XLS file here's a screen shot
www.robgray.com/temp/Arduino-shield-pins-used.png
The table details many shiilds and the pins they use.
I spent hours looking at schematics (where available) and also used info from Mowcius' site and the Arduino site, but don't treat the list as gospel, many schematics are confusing plus I got a bit cross-eyed after a while. Also some schematics were in a version of Eagle I coudn't read.
Hopefully one day we can build on this to provide a comprehensive resource.
Rob