Add rotary encoder?

[cjsha]

This came from a discussion during tech talk about mitigating twist due to sensor drift. I think Aaron was specifically referring to a rotation index (which we can use a Hall Effect sensor for), but there are also rotary encoders that fit in the back of steppers.

[cjsha]

If we do this, I think it would be worth adding a motion controller that internally takes care of closed-loop feedback motion, i.e. TMC4361. Though this IC does not replace the TMC2130 driver, it's used in addition to the TMC2130 (or TM2240 with improved "stealthchop"). Maybe TMC5271 would serve well in this situation.

This would simplify the firmware.