While I'm working on my own arduino based oscilloscope (someday, someday...), I would like to share one really helpful tool to analyse your generated audio signals in case you don't have a real oscilloscope by hand.
Its called iSpectrum, and you can find further info and download it on its website
Unfortunately, its only available for Mac, but for sure there are thousands of applications like this one for other platforms. I've been using this one for a while and it is pretty nice since it includes a real time oscilloscope with some basic configuration parameters and a really useful real time FFT calculator to get a nice home-made spectrum analyzer.
Probably many of you already knew about these kind of tools, but I think that anybody working at home with the pedalSHIELD should know about this!
Do you know of any other better than iSpectrum, or at least capable to run on other platforms?