Thanks for the prompt reply.
Everything is working correctly now. Feel free to skip over my ramblings below.
Anyway, thanks for all the awesome gadgets you all create & sell, your patience with my verbose narratives, and most importantly, providing excellent and timely support to your customers and the community. Your time, skills, and passion are very valuable, and I appreciate your willingness to share them with all of us.Details:
Turns out I made quite the rookie mistake, but your reply prompted me to verify that I was using a pullup resistor.
I was actually configured using a pulldown resistor, which appeared to be working, but didn't make sense the more I thought about it (as the breakout board clearly states that SEL shorts to GND when pressed).
I was trying to get one component working, and then incrementally add each additional component in turn.
I had the RGB LCD working (with its own sketch), and I added the wiring for the Thumbstick, and was only using the Debounce code example before integrating it into the other sketch.
However, when I added the wiring for the Thumbstick to the already wired LCD, I wasn't consistant with my color choices.
I'm using 4-wire intercom wiring from RadioShack for my longer runs, and its wires are Green-Red-Black-White.
On the RGB LCD (with i2c backpack), I have Red=Vcc, Black=GND, Green=DAT, White=CLK.
A second length of wire uses Red-Green-Black, and they are connected directly to the last 3 pins on the RGB LCD for Red-Green-Blue (backlight) control.
When I added the Thumbstick, I cut a section of Red-Green to wire into the breakout board as Red=Vcc, Green=GND (and unrelated, but a section of Black/White and a single White, where Black=SEL, White1=X, White2=Y).
So when I went to tie in a short run from the Thumbstick's Vcc/GND to the RGB LCD (which has the longer run), I connected Red to Red (okay), and Green to Green (which was the DAT connection, not GND). So whatever I was connecting to, certainly wasn't GND, and was probably a floating input (undefined in the debounce sketch), and it was reading HIGH, and my pulldown resistor configuration appeared to be working.
A continuity test on the Thumbstick breakout showed some resistance between Vcc & Ground when SEL was open, and full continuity when closed, so I'm sure my Arduino probably didn't appreciate that.
After getting your reply, I had to figure this out before going to bed, as I wouldn't be able to sleep knowing I couldn't get the simple button example working.
Tomorrow I'll redo the button wiring with Red/Black so I'm not totally confused when I have to make a change 6 months from now!