add missing pins to pins_CHITU3D_V9.h

[ellensp]

Description

In #22401 two pins where lost in the commit shuffle.
#define Z2_STOP_PIN PA13
#define Z_MIN_PROBE_PIN PG9

This adds them back

Support for Z2_STOP_PIN, Z3_STOP_PIN and Z4_STOP_PIN was also missing. Added this also

Requirements

#define MOTHERBOARD BOARD_CHITU3D_V9

Benefits

Z2_STOP_PIN and Z_MIN_PROBE_PIN work as expected

Related Issues

#22401

[ellensp]

I notice that Z2_STOP_PIN is not in Marlin (apart from two pins files)
I suspect this is not a supported pin as of yet.

[thisiskeithb]

I notice that Z2_STOP_PIN is not in Marlin

I always thought “stop” pins were used when there was only a single endstop for a given axis or if both min and max endstops shared the same pin.

[ellensp]

@thisiskeithb that is correct
For Z with multiple Z motors and endstops, each is a separate axis (almost, at least from my point of view)

[thinkyhead]

Maybe this PR should be the start of a consolidation for endstop pins. The Conditionals_post.h file provides handling that works like this…

    #ifndef Z2_MIN_PIN
      #if Z2_USE_ENDSTOP == _XMIN_
        #define Z2_MIN_PIN X_MIN_PIN
      #elif Z2_USE_ENDSTOP == _XMAX_
        #define Z2_MIN_PIN X_MAX_PIN
      #elif Z2_USE_ENDSTOP == _YMIN_
        . . .
      #endif
    #endif

The "XX_USE_ENDSTOP with board-based endstop shorthand" approach is currently used to avoid assumptions (and entanglements), as, for one thing we didn't have E-axis endstops until recently so we were never auto-assigning the X2 endstop to the E endstop corresponding to the next free E stepper. (That would be a possibility to make extra-endstop auto-assignment predictable for those cases, but is a whole other slice of code.)

The original reasons for XX_USE_ENDSTOP are lost to obscurity, but these options are meant to avoid users directly setting XYZ extra-endstop pins in configurations, so that if you change boards the same configuration can be applied. That whole complex can be re-examined with a look at where it is now applied in the examples, and see whether such care is needed since we encourage direct assignment of a lot of pins. Endstops are fundamental, so maybe they deserve the extra care taken in how they are configured.