Add BLTouch support

Adds BLTouch support to the configuration with Z-homing DISABLED. This
Configuration should be roughly identical to the firmware-bltouch.bin
image provided in BIGTREETECH's repo for the SKR Mini E3.

Marlin/Configuration.h

@@ -1275,10 +1275,10 @@
  * The probe replaces the Z-MIN endstop and is used for Z homing.
  * (Automatically enables USE_PROBE_FOR_Z_HOMING.)
  */
-#define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN
+// #define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN
 
 // Force the use of the probe for Z-axis homing
-//#define USE_PROBE_FOR_Z_HOMING
+// #define USE_PROBE_FOR_Z_HOMING
 
 /**
  * Z_MIN_PROBE_PIN
@@ -1332,7 +1332,7 @@
 /**
  * The BLTouch probe uses a Hall effect sensor and emulates a servo.
  */
-//#define BLTOUCH
+#define BLTOUCH
 
 /**
  * MagLev V4 probe by MDD
@@ -1484,7 +1484,7 @@
  *     |    [-]    |
  *     O-- FRONT --+
  */
-#define NOZZLE_TO_PROBE_OFFSET { 10, 10, 0 }
+#define NOZZLE_TO_PROBE_OFFSET { -42, -5, -3.25 }
 
 // Most probes should stay away from the edges of the bed, but
 // with NOZZLE_AS_PROBE this can be negative for a wider probing area.
@@ -1874,17 +1874,17 @@
  */
 //#define AUTO_BED_LEVELING_3POINT
 //#define AUTO_BED_LEVELING_LINEAR
-//#define AUTO_BED_LEVELING_BILINEAR
+#define AUTO_BED_LEVELING_BILINEAR
 //#define AUTO_BED_LEVELING_UBL
-#define MESH_BED_LEVELING
+// #define MESH_BED_LEVELING
 
 /**
  * Normally G28 leaves leveling disabled on completion. Enable one of
  * these options to restore the prior leveling state or to always enable
  * leveling immediately after G28.
  */
 //#define RESTORE_LEVELING_AFTER_G28
-//#define ENABLE_LEVELING_AFTER_G28
+#define ENABLE_LEVELING_AFTER_G28
 
 /**
  * Auto-leveling needs preheating
@@ -2091,7 +2091,7 @@
  * - Allows Z homing only when XY positions are known and trusted.
  * - If stepper drivers sleep, XY homing may be required again before Z homing.
  */
-//#define Z_SAFE_HOMING
+// #define Z_SAFE_HOMING
 
 #if ENABLED(Z_SAFE_HOMING)
   #define Z_SAFE_HOMING_X_POINT X_CENTER  // X point for Z homing

Marlin/Configuration_adv.h

@@ -1613,7 +1613,7 @@
    *  - SDSORT_CACHE_NAMES will retain the sorted file listing in RAM. (Expensive!)
    *  - SDSORT_DYNAMIC_RAM only uses RAM when the SD menu is visible. (Use with caution!)
    */
-  #define SDCARD_SORT_ALPHA
+  // #define SDCARD_SORT_ALPHA
 
   // SD Card Sorting options
   #if ENABLED(SDCARD_SORT_ALPHA)

platformio.ini

@@ -13,7 +13,7 @@
 [platformio]
 src_dir      = Marlin
 boards_dir   = buildroot/share/PlatformIO/boards
-default_envs = mega2560
+default_envs = STM32F103RC_btt
 include_dir  = Marlin
 extra_configs =
     Marlin/config.ini