I have already installed the Arduino Mega in our party room to control the lights and air conditioning and it works fine.
Now I have done another project (internet-enabled alarm clock) and since I don't need it anymore (unless someone here wants to by it for 100€ ? :P) I want to use the Ethernet shield to enable us to control the lights using our smartphones like I did when presenting my alarm clock. So I connect the Ethernet shield to an old WiFi router and this broadcasts the settings menu throughout the air to the smartphones.
My question is: Do I need any additional I/O pins for the Ethernet shield when NOT using (and of course not having one plugged in ) the SD card?
I read I need the Pins 4, 10, 11, 12 and 13 for the Ethernet shield thing but only when using the SD card? Since the wiring is already there and stuff I would just want to plug the ethernet shield on, upload the sketch, plug in the ethernet cable and all done.
"Arduino communicates with both the W5100 and SD card using the SPI bus (through the ICSP header). This is on digital pins 11, 12, and 13 on the Duemilanove and pins 50, 51, and 52 on the Mega. On both boards, pin 10 is used to select the W5100 and pin 4 for the SD card. These pins cannot be used for general i/o. On the Mega, the hardware SS pin, 53, is not used to select either the W5100 or the SD card, but it must be kept as an output or the SPI interface won't work.
Note that because the W5100 and SD card share the SPI bus, only one can be active at a time. If you are using both peripherals in your program, this should be taken care of by the corresponding libraries. If you're not using one of the peripherals in your program, however, you'll need to explicitly deselect it. To do this with the SD card, set pin 4 as an output and write a high to it. For the W5100, set digital pin 10 as a high output."
) the SD card?