Yes, nice find Michael! One less component is always good. Those tiny X4Rs are great, full range with replaceable antennas, and full telemetry.
Norbert, you can get any Tx channel to send any PWM range you want by adjusting end points. E.g. you could use a toggle switch just as well. Even on the X4R with only first 3 channels as PWM this shouldn't be a problem.
This has nothing to do with AQ at all, except that you want to match the same range as configured for Motor Minimum and Maximum PWM settings. Which, BTW, is very conservative -- you could easily go to 900-2100 and get higher overall resolution.
I'm confused by the OP -- inverting the S-Bus signal shouldn't affect the actual channel values at all. Regardless, to calibrate ESCs you just plug the ESC into the Rx directly (or all of them at once with a splitter). No AQ involved.
I was using a Hitec HPP-21 servo programmer the other day and realized it has a test mode which outputs precise PWM pulses (via a GUI on a computer). With a variety of modes and user-defined positions and end-points. Would be perfect to calibrate ESCs or even do motor thrust calculations. < $30.
My point is that any precise servo tester with a digital pulse display should work, or any other device capable of outputting a defined PWM pulse (fairly common in the RC world
).
-Max