The idea behind automatic calibration and bed leveling is fairly simple. The controller uses the Z-probe to tap the print surface in a grid. The depths at each point are then fed into a couple of algorithms that know how to turn a depth-map into a useful calibration.
I'm choosing today to post this thread because I think the probe is really "done" now. It's been around since 2013, gone through a few design revs, etc., but I think this is the last upgrade that will be needed. I added two mounters, one for on top of the effector and the other for below it, that constrain the probe and stiffen it significantly, so that the probe's wiring can't bend the probe as it moves around. Additionally, the bottom mounter has extended "feet" that project just a little bit past the end of the probe. If a loose wire or a firmware crash prevents your controller from reacting to a probe hit, and tries to drive the probe into the print surface, the "feet" will transfer the load to the effector, so you don't snap the delicate mount on the probe itself.
I think I will work on FSR-based probing after this.
