ultrasonic-poc VS ESC

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.

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

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)

See here and here for an example from my ESC project, or this example from Teacup

In this project for example, I use timer1 for dual channel 10-bit PWM at 7.8KHz for example, although I also have a system clock and a servo pulse reader hooked to it.

It is possible to get a timer to do multiple things at once if you work out how to set it up for overlapping use cases and then poke the registers yourself - eg in this project I use timer1 to 1) read a servo PWM signal, 2) generate two channels of motor drive PWM, and 3) keep a system clock

Sure, one of my first custom PCBs was a DC motor driver - album, github

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

You can see an example of using timer input capture to read a servo PWM signal in this old project of mine

I've encountered plenty of folk that'd like to read a servo PWM signal and generate motor drive PWM at the same time in a less janky way than pulseIn (which blocks on no signal and is affected by interrupt latency) and analogWrite (which uses a super low PWM freq by default)

This ancient project of mine may give you some hints on interrupt-driven ADC readings, but it doesn't use free-running mode because I have multiple inputs to read.