Once you learn how to read Morse code, you might want to teach your Arduino to understand it, too. Or, you can check out some other Morse-based projects.

This project uses two Arduino to communicate with each other using light by means of Morse Code. As a more advanced project, it has some complex array usage and investigates converting switch inputs ...

It’s thus a surprisingly simple project, and the write-up spends far more time proselytizing the art of the carrier wave than it does on Arduino code.