A command 'ph' is implemented to spew phonemes to the synthesizer, enabling basic experiments over the terminal.
Having gotten the SP0256 task in place, now it's time to use it. My eventual plan is to have the BluePill accept a binary stream over the serial port and directing it into the SP0256, but that will mean making a client side app (I guess I could make one quickly enough with python -- surely there is serial IO capability there).
In the short term, though, I decided I can implement a command on the command processor. This command takes a hex sequence which is the stream of phonemes. Since it's on the command processor, it's quite limited (the command processor has a hard line-length limit of 128 chars), but it's quite serviceable for interactive testing.
Because of the line length limitation, I shortened the name of the command to 'ph' and it takes a contiguous stream of hex chars. E.g., sending:
Will cause the synth to speak 'hello'.
In the strictest sense, I have now achieved what was my original motivation for doing this project: set up to cause the real synth to generate audio that I can record, but of course the project has grown beyond that motivation and now I'm off chasing geese.
Chase geese, maybe binary steaming of phonemes over the serial port (instead of the textual way here), or maybe text-to-speech.