I learned that the Bus Pirate can be used as an AVR programmer, so if I make my own circuit with an AVR then I shouldn't need to buy a separate programmer for it. I updated the firmware on the BP to the latest community version. I also wrote functions for the waves to return a float between -1 and 1 which I can change the amplitude on and it's working great. Triangle wave was a little different than I thought because it is either rising or falling. I now have it providing around 6000 samples of data per cycle, but I think I can squeeze some more out of it if I am able to use an interrupt timer instead of a delay. I used a similar technique when I was developing the robot board that read PWM signals on 6 channels that I needed very tight timing on.