Here you’ll find code (Python and AVR-flavored C) for an upcoming Make Magazine skill-builder section on using USART serial for two-way communication between the microcontroller and your desktop (for fun and/or profit).
The main.c code for the AVR and the webLauncher.py routine for your desktop
computer speak to each other using a tremendously simple protocol: sending an
"L" to the AVR tells it to toggle the LED on and off, and sending an "X" to the
desktop instructs the Python routine to open up a website. Add a button and
LED to the AVR and you can be notified when something changes on the computer
side, and react to it with a button press.
So far, so good. It was the most I could squeeze out of just a few lines of code.
Along the way, we get to learn stuff about setting up the AVR’s serial peripheral hardware: setting baud rates, enabling transmit and receive, how to queue up bytes for transmission, etc. Solid tutorial material.
From here, it only takes a little more work to flesh this out into something that you’d be willing to have on your desk.
Included are Python routines that check some websites (XKCD and Hack-a-Day respectively) to check if there’s new content, and light up the LED if so. Then, with a button press, the new material is loaded into a browser, the LED turned back off, and the Python routine waits for the next change again.
All that’s left to build up a nice project is a cool enclosure, a swanky (multi-colored?) LED, and a solid button. Have more LEDs and buttons? You can track more websites.