An R-2R resistor ladder is a nice little method of doing digital to analog conversion.
The one I made is 8-bit, so it can output 256 different voltages from 0V to 3.3V. Here are some pics:


You can see on my oscilloscope that I'm generating a saw wave. All I'm doing is counting from 0 to 255 really fast over and over again, and putting the number onto the 8 pins of the PIC that are connected to the resistor ladder. You can also see on the oscilloscope that the wave isn't perfectly straight, and that's because of the resistors' tolerance that is differing the resistance slightly. There's nothing I can do to fix that, except use resistors with smaller tolerance.

Here's a close up pic of the ladder:


If you want to learn more about this take a look at the wikipedia page here.
Nice job! What oscilloscope is that? I'm glad to see you're messing around with some electronics development, and learning how D-A conversion actually works, at least on a crude level, is superb.
Kerm: The oscilloscope is a Velleman Instruments HPS-10.

I'm also thinking of making sound with this. The only things I'd need to put on the outside of this would be a transistor and a speaker, and I could be making some 8-bit music Very Happy
  
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