ultrasonic-poc VS SunriseLight

That's why I don't use them for anything fancy

Heh, ultrasonic phase offset can be done with an Arduino's analog comparator (NOT the ADC which is too slow) - here's one I prepared earlier

hackaday.com has a zillion links to examples; here's one two three four of mine and I've also got a laundry list of companies I've helped but whose technical details I can't legally publish (note that I've assisted many but not all of the companies in that link)

HC-SR04 can't, but the transducers on it can - here's a proof-of-concept I threw together a while ago to play with them, although you may want a capacitor in series with R6 if you want it to work over longer distances than ~10cm or so

PS: https://github.com/triffid/ultrasonic-poc may interest you ;)

If you're curious here's a couple of my AVR projects (not using Arduino libraries at all), and here's an NRF52 one

ChatGPT often gets stuff wrong and likely can't handle more advanced programming techniques (eg this sort of thing), so it's only going to be useful for basic stuff and shouldn't be used beyond your ability to critically analyze or debug code.

Does this proof of concept where I get absurd precision (at short range) from a couple ultrasonic transducers salvaged from a HC-SR04 and a few resistors count?

Here's a random proof-of-concept I threw together a while ago for super precise ultrasonic wind speed measurement (or very short distances) - it uses the analog comparator plugged into timer input compare for phase analysis, which is where the precision comes from.

Redshift has code to calculate that locally which I use in my sunrise light project

Since then I've made lots of things like audio amplifiers and effects, motor controllers, 3d printer controllers and firmware (and subsequently smoothieboard), muscle stimulators, bluetooth LED strip controllers, etc

Here's a bluetooth RGB strip controller I made a couple years ago if you want an example.

hackaday.com has a zillion links to examples; here's one two three four of mine and I've also got a laundry list of companies I've helped but whose technical details I can't legally publish (note that I've assisted many but not all of the companies in that link)

eg for this project my available inputs were intermittent 12v power, bluetooth, and the current time and location; and the desired output was 3× high current low-side switches that produced 12v RGB PWM corresponding to the colour temperature and brightness of the sky - so we need a bluetooth microcontroller, battery backup to keep time when 12v is absent, some battery management which wanted 5v in, a 12v buck to feed it, some MOSFETs, and redshift or similar code to plug into things.

Here's one I made earlier although it targets NRF52 and doesn't use Arduino libraries.

I've got a similar project here, and most of the complication is for battery management - the actual LED strip drive is even simpler than yours because I chose MOSFETs that work nicely with 3v3 gate voltage :P

If you're curious here's a couple of my AVR projects (not using Arduino libraries at all), and here's an NRF52 one

I guess my Sunrise Light project could have been built on Arduino's libraries since an NRF52 core exists, but I didn't do that…

For example, this old project of mine uses an NRF52832 (which is substantially similar to the '840, just missing USB) and it offers several services and characteristics including a battery level service, a DFU service, and a custom service for actually controlling it.