Serial communication between two Arduino boards
Getting two Arduino boards to talk to each other opens up projects that a single board can't handle on its own. You might have one board reading sensors in one corner of a room and another driving a display somewhere else, and the two need to share what they know. Serial communication is one of the simplest ways to make that happen, and it works with almost any Arduino model you have lying around. This article walks through connecting two Arduino Nano boards and passing data back and forth over their serial ports.