Capacitive Touch Sensors on an AVR without QTouch (Let's Learn and Code 3)

I've received a number of requests about how I do my touch sensors. I decided to finally post the full how-to on it. This is my third in my let's learn/let's code series, and my first one where I am combining them into one video (since it was short enough).

Source code is available here: https://github.com/cnlohr/magfestbadg...

Since the schematic at 7:00 is somewhat confusing, and for explaination purposes I should have wired the capacitor to ground, the circuit still works even with it wired to 5V. It is because the voltage slope becomes shallow as the voltage across the resistor decreases:

I did a spice just to make sure: http://imgur.com/gALkRea