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?


  • Yep, you need Bi-directional logic voltage converter learn.sparkfun.com/tutorials/…
    – Martynas
    May 17, 2017 at 15:28
  • @martynas those are more geared towards I2C, since I2C has a bidirectional data line.
    – Gerben
    May 17, 2017 at 15:33
  • Wooow nice!!! yes I have seen those Bi directional logic voltage converters now I know whats that for. Appreciat it
    – VAAA
    May 17, 2017 at 15:39
  • And I guess that logic voltage converters are only used for the Pins right... for powering the module then is right to use a voltage regulator such as the LM3940 IC.
    – VAAA
    May 17, 2017 at 15:40
  • Yup you are correct. May 17, 2017 at 16:02

1 Answer 1


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.

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