If you're not an EE - a function generator is a pretty common piece of electrical engineering lab equipment.
I've got all the source files up on GitHub - feel free to take a look: https://github.com/cushychicken/bfunc
I've also been keeping a weekly project journal. I just posted the latest installment today if you'd like to see what I've gotten up to: http://cushychicken.github.io/bfunc-weekseven-log/
I'm already planning a second prototype and board spin with more functionality.
If you need or want a really bare-bones function generator for your home lab, get in touch! Instructions for how are in the post. )