🩹 Fix Chitu3D V6 default probe pin (MarlinFirmware#25552)

Author: ellensp

Marlin/src/pins/stm32f1/pins_CHITU3D_V6.h

@@ -33,4 +33,55 @@
   #define FIL_RUNOUT2_PIN                   PF13
 #endif
 
+#ifndef Z_MIN_PROBE_PIN
+  #define Z_MIN_PROBE_PIN                   PG9
+#endif
+
 #include "pins_CHITU3D_common.h"
+
+/*
+ * Circuit diagram https://github.com/MarlinFirmware/Marlin/files/3401484/x5sa-main_board-2.pdf
+ *
+ * Details on the 30 pin ribbon pins. From: https://3dtoday.ru/blogs/artem-sr/tronxy-x5sa-pro-ustanovka-bfp-touch-na-board-chitu3d-v6-cxy-v6-191017
+ *
+ * JP2 Ribbon 30 on CXY-V6-191017
+ * ----------------------------------------------
+ * | 2  4  6  8 10 12 14 16 18 20 22 24 26 28 30|
+ * | 1  3  5  7  9 11 13 15 17 19 21 23 25 27 29|
+ * ----------------------  ----------------------
+ *
+ *  --------------------------------------------------------------------------------------
+ *  | Pin | Label     | Function & Notes                                                 |
+ *  --------------------------------------------------------------------------------------
+ *  |   1 | Hotend    | Hotend driver Q6 HY1403 via MCU Pin127 PG12                      |
+ *  |   2 | Hotend    | Hotend driver Q6 HY1403 via MCU Pin127 PG12                      |
+ *  |   3 | Hotend    | Hotend driver Q6 HY1403 via MCU Pin127 PG12                      |
+ *  |   4 | Hotend    | Hotend driver Q6 HY1403 via MCU Pin127 PG12                      |
+ *  |   5 | +24v      | Hotend +24v                                                      |
+ *  |   6 | +24v      | Hotend +24v                                                      |
+ *  |   7 | +24v      | Hotend +24v                                                      |
+ *  |   8 | +24v      | Hotend +24v                                                      |
+ *  |   9 | F_2       | Extruder Fan2 driver Q8 AO3400A X07S via MCU Pin129 PG14         |
+ *  |  10 | +24v      | Extruder cooling Fan2 +24v                                       |
+ *  |  11 | F_1       | Part Fan1 driver Q7 AO3400A X07S via MCU Pin128 PG13             |
+ *  |  12 | +24v      | Part cooling Fanl +24v                                           |
+ *  |  13 | 1B        | X-MOTOR Winding Drive                                            |
+ *  |  14 | 1A        | X-MOTOR Winding Drive                                            |
+ *  |  15 | 2B        | X-MOTOR Winding Drive                                            |
+ *  |  16 | 2A        | X-MOTOR Winding Drive                                            |
+ *  |  17 | lA        | El-Motor Winding Drive                                           |
+ *  |  18 | 1B        | El-Motor Winding Drive                                           |
+ *  |  19 | 2B        | El-Motor Winding Drive                                           |
+ *  |  20 | 2A        | El-Motor Winding Drive                                           |
+ *  |  21 | PROXIMITY | 10kΩ Pullup to +5V and 100nF to GND, then 20kΩ to MCU Pin124 PG9 |
+ *  |  22 | +24v      | Proximity sensor +24v                                            |
+ *  |  23 | +5V       | Filament sensor +5V XSTOP sensor +5V                             |
+ *  |  24 | GND       | Proximity sensor GND                                             |
+ *  |  25 | FILAMENT1 | 10kΩ Pullup to +5V and 100nF to GND, then 47kΩ to MCU Pin110 PA15|
+ *  |  26 | GND       | Filament Sensor GND                                              |
+ *  |  27 | XSTOP     | 10kΩ Pullup to +5V and 100nF to GND, then 47kΩ to MCU Pin125 PG10|
+ *  |  28 | GND       | XSTOP sensor GND                                                 |
+ *  |  29 | GND       | Extruder temperature NTC sensor return GND                       |
+ *  |  30 | ETEMP     | 4k7Ω Pullup to +3V3 and 100nF to GND, then 4k7Ω to MCU Pin35 PA1 |
+ *  --------------------------------------------------------------------------------------
+ */