Thanks microfunguy.
I think you've confirmed some methods for me. And 'yes', that branching example does help... it makes a little bit of sense after I 'looped' myself to reread it.
So I think these combinations will work as Input to Arduino or Pic circuit
you said:
played with generating LED pulses from the camera to microcontroller
Sorry to mislead you. While that blue-LED communication method may come in handy for expanding set-up later, what I meant and should clarify is this: I will have keyfob buttons that will issue the '16 commands' (what should I call them?) by RF tx/rx to the Pic/Ardu.
Thanks to your help, I conclude that on the microcontroller output I will only need 8 diff pulse widths. I was unsure of the timing and limitations up to now, about the range of pulses I could use. So now I know how uBasic will branch on that information,I will use 150ms, 180, 210, 240 pulses uC output to tell SDM script that I pressed which remote button A/B/C/D as mutually exclusive 'cases'.
Then I'll use the shorter pulses (but >30ms) out of uC for executing camera settings or actions, using my 4 'numbered' RF buttons. Pressing '2' after 'A' was previously pressed... would be say 'focus' action.
But same button '2' after 'B' had been pressed... would be to increase shutter speed for example... (multiple presses probably). I'm thinking to add a timeout would set things back to Case 'A', so always ready to shoot.
See these examples using a commercial RC receiver
The R/C switches and controllers/receivers won't help me here, but I appreciate the pointer to the code and how the conditional branching is implemented. It seems the test values are stepped (mentally multiply by 10msec?).
more clever way of doing this is to send coded commands... using an ATtiny
'Yes', would be neat to send specify settings/parameters and get things executed in SDM. But that's beyond my scope to due patience, knowledge, ~ADD limitations.

All-in-all... a big thanks. I was afraid I'd have to do some fancy button-pressing, like A>>D>>B, just to set up one branch case. This is going to be much more manageable and also somewhat predictable as to what 'state' the camera gets to.
Look forward to your blinking LED in future maybe... could be good to 'hear' remotely what setting was set.