What does it happen if I wanna use the digital pins 10, 11, 12, 13 as a output/input in my project with the ethernet shield plugged onto the UNO but without using the ethernet functions? I meant I wanna avoid plugging and unplugging the ethernet shield every time I don't wanna use it.
If you don't include the Ethernet library in your sketch, and don't initialize the Ethernet class, then those pins are available for other uses. Just don't use the SD card, either.
Ok... But is there any risk to damage the ethernet shield? Thanks paulS for your support! :)
But is there any risk to damage the ethernet shield?
If you don't do anything that would also damage your Arduino (like applying over voltage to one of the pins), your Ethernet shield is not in risk.
Careful on that! With the ethernet shield connected, and if D10 is LOW, the MISO (D12) line on the w5100 will go to OUTPUT. If you have an OUTPUT device on that pin expecting all on D12 to be high impedance, that would be incorrect, and possibly damaging to one of them.