init max endstop pins if corresponding flag USE_MAX is enabled

[Le0Michine]

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Description

Added init max endstops for scenario when user wants to use USE_XMAX_PLUG, USE_YMAX_PLUG or USE_ZMAX_PLUG and doesn't have SENSORLESS_HOMING enabled (ie STALL_SENSITIVITY is undefined).

Benefits

The use case is dual Z motors which require usage of one of those MAX plugs for the second Z_MIN endstop. If neither of MAX_PIN parameters defined compilation fails with a simiilar error

#error "Z2_USE_ENDSTOP has been assigned to a nonexistent endstop!"

Configurations

Here is the related parameters

Configuration_adv.h

// #define SENSORLESS_HOMING // StallGuard capable drivers only
...
#define NUM_Z_STEPPER_DRIVERS 2
....
#define Z2_USE_ENDSTOP          _YMAX_

Configuration.h

#define USE_YMAX_PLUG

Related Issues

I didn't see any related open issues.

[ellensp]

SKR 1.4 does not have max plugs
It has x,y and Y endstop plugs plugs and e0-det, e1-det and pwr-det and if you try an use anything else in these plug the diag pins from e0 and e1 stepper drivers will interfere with it.

[Le0Michine]

According to BTT docs diag pins are supposed to be cut to avoid that in case sensorless homing is not used as it would interfere with x, y and z min. It seems for E0, E1 one would also need to cut diag pins to be able to use filament runout sensors.

Besides in the code E0_DET E1_DET and PWR_DET were already assigned as X_MAX_PIN, Y_MAX_PIN and Z_MAX_PIN in lines 59, 70 and 81 respectively.

Do you see any particular reason why not to set X_MAX_PIN, Y_MAX_PIN and Z_MAX_PIN in case when STALL_SENSITIVITY is not defined?

[thinkyhead]

Do you see any particular reason why not to set X_MAX_PIN, Y_MAX_PIN and Z_MAX_PIN in case when STALL_SENSITIVITY is not defined?

For one thing, they can't serve that function. If the X axis homes to max then the X_STOP_PIN is the X max endstop. I don't see the value of forcing the X endstop of all machines that use this board to connect to the E0_DIAG_PIN when homing to max. Each axis only needs a single endstop plug. The existing exposure of the "other" pin as the "other endstop" pin was provided by request, and is exactly opposite of the effect of this PR.

[Le0Michine]

@thinkyhead for some configurations it is required to have multiple endstops for a single axis, a good example of that is dual Z motors. In Configuration_adv.h it is possible to use MAX pins as extra endstops however that won't work unless they are initialized which is currently happening only when sensorless homing is enabled. I find it unclear why those pins can serve the purpose of X_MAX plugs when stallguard is enabled and can't when it is not, would appreciate it if you could clarify that to me. My understanding is that it won't be used as MAX plug unless user explicitly enables it, same goes for filament runout, so user still can use those ports for either of functions. But not having them defined in the pins files essentially blocks user from using dual Z axis without sensorless homing and fails compilation with an unclear error.

I also wanted to bring your attention to the fact that in SKR 1.3 has exact same plugs set for the endstop the only difference is the labels, please refer the links below to see the exact same assignment of pins as in this PR (same pin assigned to x_max and filament runout). Would that resolve your concern regarding my change?

https://github.com/MarlinFirmware/Marlin/blob/2.0.x/Marlin/src/pins/lpc1768/pins_BTT_SKR_V1_3.h#L47
https://github.com/MarlinFirmware/Marlin/blob/2.0.x/Marlin/src/pins/lpc1768/pins_BTT_SKR_V1_3.h#L94