Booya! Proof of concept successful. LEDs dim and brighten as expected. Still not sure what the actual implication is that the PWM signal is 3.3V vs. 5V, especially given that the circuit is not treating the PWM as a digital signal but as some analog tweak to the feedback loop.
@twopoint718 @josecastillo@adafruit Check around the GitHub for Adafruit’s free license PTC code too. The contributors there like @PaintYourDragon might have pointers.
@twopoint718 @josecastillo@adafruit I never got around to a write up of how I did it. If I recall correctly ladyada of @adafruit herself did a video of walkthrough of her approach to cracking the same code on YouTube. My methods were slightly different but hers clearly worked well.