FYI, Klipper has an infrastructure for precision timing of adxl345 measurements.
At a high-level, the adxl345.py code works with the sensor_adxl345.c code to read measurements from the adxl345’s buffer in such a way that we can estimate the sample time with very good precision. The “motan” tool ( Debugging - Klipper documentation ) demonstrates how one can then correlate these measurement times with past stepper positions.
We’ve used this system in various accelerometer tests and there is good confidence that the timing correlation works well.
I’ve also implemented similar functionality for high-precision timing of magnetic angle sensors ( Experiment with hall effect angle sensors ).
Separately, I agree your probing branch is interesting, and I do hope to get time to review it.
Cheers,
-Kevin