ultrasonic-poc VS QingStation

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.

I've been inspired by this github to attempt to recreate an ultrasonic anemometer using HC-SR04 (or RCWL-1601 for 3.3V microcontrollers - ie PI PICO). My biggest issue right now is getting accurate pulse widths less than 4us - which is a limitation of micros(). I know that perpendicular wind can affect these sensors ( see conference article). I want to be able to get the pulse widths from echo pin at resolutions of at least 1 - 2 cpu clocks.