Overall, I work hard to segregate things out into their individual constituant components. Very much like Object Oriented programming, things should all be self contained inside their own entity. This makes it (in theory) very easy to remove something from your system and ONLY comment out that include file. If you can not, then you have something wrong in your hierachy thinking. I've done a LOT to try to enable this to function and NOT refer to other MCU pins that are NOT defined in your section. It could be argued that some macros belong in more generalized areas, but if it deals with movement of the heads or moving the table/bed up/down, I believe THAT particular function belongs in motion.cfg.
All of the pin definitions for a given MCU should be in that area. For example, there is an EBB36 MCU on the XOL toolhead. All of the fans connected to that toolhead should be defined in there, of another file included from there like xol_fans.cfg.
You could argue that putting toolhead fans in the xol.cfg breaks the idea of a "universal" fans location in the fans.cfg and probalby you'd be right (and even toolhead led's are in the xol.cfg, but the chamber led's are in their own led.cfg). Technically, I should have made a manta.cfg under hardware.cfg and then put motion.cfg and fans.cfg and bed.cfg all below that, and you could then have fans and led below XOL as well to be more clear. Here, each item in 🔴red🔴 has it's own MCU on the canbus.
To that end, I have moved all my configs toward this later approach:
But as it stands now, to swap between StealthBurner and XOL toolhead, even with all the different toolhead MCU boards, IOs, different fans and pin defs and stuff, it is as simple as comment OUT XOL.cfg and uncomment stealthburner.cfg in hardware.cfg include list. Or really, to power up the printer and have it functional, without the TOOLHEAD MCU connected or even on the printer. And all of the [input shapper] and hotend PID heater tunes go in each toolhead config. NOT in printer.cfg.
I also have managed to REDEFINE sections (like x endstop_pin:) that will change once you get to the toolhead include, but the motion.cfg needs a valid PIN before (or if there is no) toolhead.cfg. For example, I define a dummy entry for x endstop_pin: PF4 in the manta board before it even knows about a toolhead MCU that the REAL x endstop_pin: THB:PB6 will be connected to, and then REDEFINE this in the xol.cfg IF it is included.
Caution
This REQUIRES that I'm VERY careful not to HOME and only issue SET_KINEMATIC_POSITION to allow manual movements to be unlocked but does allow me to move my bed up/down and gantry around even without the XOL toolhead plugged in or on.
Example motion.cfg
[stepper_x]
step_pin: PE6 # X-axis motor pulse pin setting
dir_pin: !PE5 # X-axis motor direction pin setting
enable_pin: !PC14 # X-axis motor enable pin setting
microsteps: 32 # Motor microsteps setting
rotation_distance: 40 # Active pulley circumference mm (2GT-20T pulley 40, 2GT-16T pulley 32)
full_steps_per_rotation: 200 # Number of pulses required for a single motor revolution (1.8 degree motor: 200, 0.9 degree motor: 400)
endstop_pin: PF4 # Use Manta Endstop 0 dummy for now when no TH plugged in
...
xol.cfg
[extruder]
step_pin: THB:PD0 # Step pin
dir_pin: !THB:PD1 # Direction pin, "!" indicates logic inversion
enable_pin: !THB:PD2 # Enable pin, "!" indicates logic inversion
full_steps_per_rotation: 200 # Number of pulses required for a single motor revolution (1.8 degree motor: 200, 0.9 degree motor: 400)
microsteps: 16 # Microsteps setting
gear_ratio: 9:1 # Gear ratio
...
# Redefine the X-motion endstop_pin!
[stepper_x]
endstop_pin: THB:PB6 # Limit switch PIN setting (X-)