* Correct over optimization of pre-initialized variables
NEAR_ZERO() works most of the time... But it leaves corner cases
uncovered. We need to explicitly check if these variables are +/-
infinity.
* Correct over optimization of pre-initialized variables
The Configuration.h file entries for BL-Touch have been updated to:
```cpp
//#define BLTOUCH
//#define BLTOUCH_DELAY 375 // (ms) Enable and increase if needed
//#define BLTOUCH_HEATERS_OFF // if defined the printer's heaters are
turned off during probe event
```
The electro-magnetic interference from the bed and nozzle are affecting
the BL-Touch repeatability for some users. This problem can be helped
by shutting down the heaters during the actual probe event and then
quickly turning them back on.
Because this code is messing with the heaters, it is written in a
paranoid manner. It only turns the heaters back on if everything is
EXACTLY as it expects things to be. The BL-Touch probe must have been
put into a deployed state less than 20 seconds prior, or the stow()
function will NOT turn the heaters on.
This code has been tested and works for both G28 and probing functions.
These are my two 'Nice' machines. Both are good example machines. The
FolgerTech i3-2020 is probably the best value kit on the market right
now. And it has developed a 'Cult Following' of hobbiests. I'll always
have an up to date Configuration.h file set for it, so it may as well be
an example configuration.
And the gCreate gMax 1.5+ is the best printer I've ever seen that runs
Marlin. For sure, I'll always have up to the minute Configuration.h
files for this printer also. I've moved over to using the gMax as my
primary development machine for Marlin. So... Besides being a good
machine, it is a nice convienience for me to have this Configuration.h
file as an 'Example'.
Also... The memory corruption issue may be fixed. The GCC compiler
was inlining static functions and this caused the G29() stack frame to
become much larger than the AVR could handle.
* relocated ubl state to config. store:
* removed a number of ubl state variables and padding which were largely unused - saved 58 bytes of both SRAM and EEPROM;
* modified ubl sanity_check - no longer checks removed state variables that were otherwise unused, where checking didn't seem to accomplish anything, ultimately;
* removed pre_initialized state, saving 64 bytes of SRAM;
* removed automatic saving of UBL state after UBL activation/deactivation;
* consolidated multiple GRID_MAX_POINTS_X/Y to 'Global Leveling' section of EEPROM;
* minor update to G29 Sx notes/instructions;
* renamed mesh load and save parameter to 'slot' from 'm' for clarity;
