Voltage divider arduino 5v and Ethernet board 3.3 I have an Arduino Nano 5v module and I just received an Ethernet Interface Board - ENC28J60 that runs at 3.3v. (https://www.sparkfun.com/products/765)

Might sound a dumb question but I will power the Ethernet board from a Voltage regulator that can deliver 3.3v but then I have to connect via SPI to my Arduino controller. I guess I can't connect my Arduino pins directly to the Ethernet board right? because HIGH in the pin will be 5v instead of 3.3v.


  Do I need to add a Voltage divider for those pins connections? And in case I need to what resistance values are the right ones to use?


Thanks
From experience with 3.3v ESP8266es with 5v Arduinos, only the signals to the 3.3v device need to be converted (5v high -> 3.3v high). A 3.3v level to the Arduino is high enough for 5v logic to still read it as HIGH. That means you can get away with just a voltage divider on each of the Arduino -> ENC28J60 pins.