The Wiznet devices... three to decide between... say...
"3.3V internal operation and 5V tolerant I/Os"
... but I see nothing to indicate that 5v can be used to power the modules.
Also, all of them connect to external units via two DOUBLE rows of pins... hard to accomodate on any breadboard I ever saw.
The http://iteadstudio.com/ device says explicitly that there is an on-board regulation, so you can use 5-12V VCC input. It goes on to confirm that the other pins are happy with either 3.3V or 5V operation level.
Obviously, there are certain advantages to dealing with "the source" of the W5100... but the secondary market players can be "hungrier". I couldn't (easily) find a link to datasheet or scematic for the Wiznet units for instance. I was wondering why they "need" 20 pins when the iStore product makes do with 10.
In my ignorance, I prefer the simplified interconnect scheme of the iStore product, and I would like to reward their initiative... but I am not experienced in ethernet interface issues... hence my "what am I missing?" post here!
Hmmm... that lead to an "interesting" hour... I finally took a close look at the Ethernet Shield (v5) scehmatic.
If I'm not mistaken, it shows the following in use by the ethernet interface.
Where I say "D10", I am referring to the line which would be affected by the Arduino command "digitalWrite(10,HIGH); (Pin names and numbers will haunt you before you go to far into Arduino hardware!) And An0 is my way of referring to what would be sampled by analogRead(0);
The point of this? Call me a coward, but I'd rather not use these pins/ signals in my software when I am also using an ethernet shield and the ethernet library!
(D13... see below)
(In addition, an LED + resistor is provided with a route to ground from the pin for D13, but this doesn't connect to the ethernet hardware anywhere. So I'd only use D13 as an output to the on-shield LED, or taking that into acount in any other use.)
Oh, hell. Wouldn't you know it? When I build my ArduServers and the ArduSimpSrv, I didn't know the shield was using these pins... and I used them to. My devices to seem to work... but more luck than design... and while they have worked for weeks, I'll be more comfortable when I've re-arranged things.
The first ArduServer, the one built around a NuElectronics ENC28J60, may be okay, and it may be using fewer signals.
Sigh. But I guess it wouldn't be "fun" if it were easy!