Use a BLDC motor as an encoder. Almost *Exactly* as I'd imagined. Combine this with anaQuad, and yer all set!
Note that anaQuad *also* works with two sources that are 120 degrees out of phase, so only two windings of the three in a typical BLDC should be necessary. Also, his technique could probably also be applied to stepper motors.
I dunno how i never seem to come up with this simple concept, myself...
"how can I measure capacitance? Drive with an AC signal, measure phase/magnitude..."
Had to learn this one by example... Simple capacitive touch switches charge the cap, then measure the time it takes to discharge...
Friggin' simple method to apply multiple pushbuttons on a single pin is exactly the same, tie them to different resistor values, charge a cap, measure the discharge time, simple ADC. Bam. I even have a well-developed project based on that (anaButtons, as I recall).
No phase/mag necessary. So, why, then, couldn't I come up with the same for inductors? Duh.
Nice goin' @besenyeim!
I'mma linking this one here so's I can come back to it when the time is right-er.