user33103: 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

user313: 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.

33103: <p>I have an <code>Arduino Nano 5v</code> module and I just received an Ethernet Interface Board - <code>ENC28J60</code> that runs at <code>3.3v</code>. (<a href="https://www.sparkfun.com/products/765" rel="nofollow noreferrer">https://www.sparkfun.com/products/765</a>)</p>

<p>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 <code>SPI</code> 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.</p>

<blockquote>
  <p>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?</p>
</blockquote>

<p>Thanks</p>
 313: <p>From experience with 3.3v ESP8266es with 5v Arduinos, only the signals <em>to</em> the 3.3v device need to be converted (5v high -> 3.3v high). A 3.3v level <em>to</em> 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.</p>
