The sensor forms an image and OpenCV detects the actual touch configuration. It appears you can use the raw data from the Arduino, too, but it might be a little harder.

Instead of using mechanical paddles, [Sebastian] brought his iambic key into the 21st century by using a touch sensor. An ATtiny45 measures the time it takes for a single metal plate to fully charge.

Another day, another Arduino project. This time it's something called SuperDuino, a tiny touchscreen powered by a coin cell battery and backed up by a tiny Arduino-Like processor. The kit can be ...