Ethernet shield question regarding voltage levels

Hi guys,

I have an Arduino Duemilanove board with the Atmega 328p MCU. This board operates at 5 volts.

Now the ethernet shield with Wiznet's W5100 operates at 3.3 volts.

So my question is how do these two guys communicate over SPI as both of them have different voltage levels? Do they use a level shifter for this purpose?


The w5100 is a 3.3v device, but it's I/O is 5v tolerant. I use the ethernet shield on my Mega2560 no problem.

thanks a lot for your reply mate!!

I'm trying to build a PCB with the w5100 and atmega328 on a single board.

using two regulators for 5v and you know any way i can operate the 328 at 3.3v?

also I have two separate resets for the w5100 and 328 with 10k pull this the right way to do it? Because i had read that w5100 and arduino had problems with reset before.