The Ethernet FeatherWing plugs into any Feather and adds hard-wired networking. To make it as cross-platform compatible as possible, we use only SPI plus one extra, configurable pin. It's not going to be gigabit (or even multi-megabit) speeds but it will work!
The WIZ5500 Ethernet chip (and really any ethernet chip) are fairly high current devices, requring about 150mA whether or not actively transmitting. The chip is powered from the 3.3V and GND pins indicated and does not have an internal regulator.
Configuration, setup, and data is received/transmitted over SPI. All Feathers have the default SPI port on the same pins, so we use MOSI/MISO/SCK in this location. They are 3.3V logic, 5V tolerant.
A Chip Select pin is also required. By default we use this pin:
Which is connected to pin #10 on Feather Teensy 3, 32u4, 328p, M4 and M0, pin #15 on ESP8266, and PB4 on WICED.
You can also get to the CS pin from the left group of breakouts. To change CS pin, solder this pad to a different pin and cut this jumper:
You can also connect to and use the IRQ and WIZ ReSeT pins. These are not used in the library and are there for advanced usage. They are 3.3V logic, 5V tolerant.