If ENDSTOP_INTERRUPTS_FEATURE is enabled this tries to set up interrupt routines
for all used endstop pins. If this worked without errors, `endstops.update()` is called
only if one of the endstops changed its state.
The new interrupt routines do not really check the endstops and react upon them. All what they
do, is to set a flag if it makes sense to call the endstop test we are used to.
This can be used on:
* ARM (DUE) based boards - all pins can raise interrupts,
* RAMPS - all 6 endstop pins plus some other on EXT-2 can raise interrupts,
* RAMPS based boards - as long the designers did not change the pins for the endstops or at least left enough,
* all boards, if there are enough pins that can raise interrupts, and you are willing/able to swap with pins dedicated to other purpose.
About Configuration.h:
・Fix the PR #4899 (ABL: Enable by type. Bilinear for all.)
Remove Duplicated contents
・Fix the PR #4305 (Custom boot screen feature improvement)
Revert from "during boot" to "during bootup" in all the example
Configuration.h
・Fix the PR #4207 (Clean up, simplify and generalize the Allen-key-probe
code.)
Resolve and relocate the duplicated definitions in Z_PROBE_ALLEN_KEY
section
・Follow-up the PR #4805 (Additional documentation of Configuration.h)
Add forgotten changes to all the example Configuration.h
Adjust spacing
About Configuration_adv.h:
Add missing description of SLOWDOWN for DELTA
Adjust spacing
Why double touch probing is not a good thing.
It's widely believed we can get better __probing__ results when using a double touch when probing.
Let's compare to double touch __homing__.
Or better let's begin with single touch __homing__.
We home to find out out position, so our position is unknown.
To find the endstop we have to move into the direction of the endstop.
The maximum way we have to move is a bit longer than the axis length.
When we arrive at the endstop - when it triggers, the stepper pulses are stopped immediately.
It's a sudden stop. No smooth deacceleration is possible.
Depending on the speed and the moving mass we lose steps here.
Only if we approached slow enough (below jerk speed?) we will not lose steps.
Moving a complete axis length, that slow, takes for ever.
To speed up homing, we now make the first approach faster, get a guess about our position,
back up a bit and make a second slower approach to get a exact result without losing steps.
What we do in double touch probing is the same. But the difference here is:
a. we already know where we are
b. if the first approach is to fast we will lose steps here to.
But this time there is no second approach to set the position to 0. We are measuring only.
The lost steps are permanent until we home the next time.
So if you experienced permanently rising values in M48 you now know why. (Too fast, suddenly stopped, first approach)
What can we do to improve probing?
We can use the information about our current position.
We can make a really fast, but deaccelerated, move to a place we know it is a bit before the trigger point.
And then move the rest of the way really slow.
