This example code passes serial data between an Arduino's serial monitor
and a device connected to an Atmega32U4's hardware UART (pin 0 and 1).
Characters sent through the serial monitor will display it back on the
serial monitor. This code was designed to send serial data from XBees
attached to FioV3's XBee sockets. The design of the FioV3's XBee sockets
use the hardware UART pins. The Atmega32U4 Serial Passthrough will work
for other Arduinos with an Atmega32U4 such as the Pro Micro, Arduino
Leonardo, and LilyPad Arduino USB.
For assistance on configuring two XBees, check out Digi's Tutorials: