Arduino Micro & Wiznet820io

I’m trying to do some troubleshooting with an ethernet device from Wiznet - the 820io. It is an Ethernet/SPI bridge. It is based on the W5200 chip, rather than the W5100, which meant I had to do this library change: GitHub - Wiznet/W5200_Arduino_Ethernet_Lib: Arduino Ethernet Library using W5200 from Wiznet

I have run the DHCP Address sketch, as well as this example for setting up a static IP:

#include <SPI.h>
#include <Ethernet.h>

// network configuration. dns server, gateway and subnet are optional.

// the media access control (ethernet hardware) address for the shield:
byte mac[] = { 
  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };  

// the dns server ip
IPAddress dnServer(192, 168, 1, 11);
// the router's gateway address:
IPAddress gateway(192, 168, 1, 36);
// the subnet:
IPAddress subnet(255, 255, 255, 0);

//the IP address is dependent on your network
IPAddress ip(192, 168, 1, 64);

void setup() {

  // initialize the ethernet device
  Ethernet.begin(mac, ip, dnServer, gateway, subnet);
  //print out the IP address
  Serial.print("IP = ");

void loop() {

I have tested both of sets of Code on the Arduino Uno, and it works fine, giving me either the static IP or an assigned DHCP IP.

However, when I run this on the Arduino Micro, I get very different results. When I open up the serial terminal for the DhcpAddressPrint example, it takes about 5-10 minutes before it will report that it was unable to get an IP. When I run the static IP example above, it immediately reports an IP of

I have tried running this code on two different Arduino Micro’s, and I see the same results. The Uno I’m testing with is using the same jumpers, ethernet connection, etc. The only difference I am making is switching the boards and specifying as such in the IDE.

Is there something different going on with the Arduino Micro/Leonardo chip setup that I need to account for? I have reviewed the documentation as much as I can, and I don’t see any specific differences about Ethernet or SPI.

A quick note on my progress:

I've found that directing pin 10 to be LOW started getting some results. Similarly, I get these same results if I tie the SS pin from the 820io to GND.

Here is where things get bizarre: the sketch I posted above to determine a static IP is supposed to always set the IP to I have found the resetting the Micro, sometimes it will think it's IP is Other times, it will have a completely different IP than I instructed it. It seems to like to be at, though I've seen it at other IPs occasionally as well.

Here is a general pattern I have observed when testing the static IP sketch: -I unplug the USB (removing all power) then plug it back in ---Opening the serial terminal, I am told the IP is -I tap the reset button on the arduino micro ---Opening the serial terminal, I am told the IP is -I press & hold the reset button on the arduino micro, or tap it multiple times ---Opening the serial terminal, I am told the IP is

The press & Hold seems key for me getting the correct result. If I simply tap it, I usually get the all zero IP, but not always. Unplugging/Replugging the USB always brings back an IP of all zeroes.