What happened to...
...have the ability to generate test signals that are effectively ASCII characters while having control over the amplitude and pulse durations and maybe the underlying clock frequency on which the pulses ride.
Hi SL4P,
Thanks for reminding us of all that - without a doubt those are still objectives within the overall goal. Given the feedback here I'm working on all the "easy"

parts first but I'd like to get back to - or move on to - a solution that would give fuller control of the various waveform attributes. I'm open to any suggestions on how to do it all including gaining control over the amplitude and pulse durations and the underlying clock frequency (especially on a bit by bit basis in addition to a byte by byte basis).
Seems to me there should be some beginner's curriculum somewhere that covers Ohm's Law, Power Supplies, the ability to create and manage waveform voltage (amplitude), frequency, pulse durations, etc. using an oscilloscope in a way that teaches A-D, decoding, etc. - maybe with Arduino hardware and software, etc. - something that would help beginners put a few key concepts together. I'm sure there is a class out there but in the meantime it gives us all something to discuss which gives us a combination of this

, that

, and the next thing

, and sometimes this

, and hopefully this overall:

EF