Given that Due has a DAC and even DMA, it seems quite feasible and perhaps even easy to implement a simple test signal generator using direct digital synthesis (DDS). It also sounds like something that surely has been attempted before by many people, but I can't find any such projects, nothing more sophisticated than this sample on Arduino.cc which uses analogWrite().
Does someone know of such a project in a form of sketch or sample code that I can use? Or is there something I haven't realized yet that makes it impractical?
See this thread, reply #10 for an example sketch of DAC conversions with a PDC DMA:
Sinewave 100k generator, DAC + PDC + Timer. - Arduino Due - Arduino Forum reply 10

ard_newbie:
See this thread, reply #10 for an example sketch of DAC conversions with a PDC DMA:
Sinewave 100k generator, DAC + PDC + Timer. - Arduino Due - Arduino Forum reply 10
Thank you very much, your Google skill is stronger than mine. Had some frustration, but also a lot of fun experimenting with those code snippets over the weekend.
Don't know if anyone may be interested, but I'll post the source code and my thoughts when I'm done with the project, including the UI.