New boards entry for the A20M

Marlin/Makefile

 else ifeq ($(HARDWARE_MOTHERBOARD),310)
 # abee Scoovo X9H
 else ifeq ($(HARDWARE_MOTHERBOARD),321)
+# Geeetech GT2560 Rev B for Mecreator2
+else ifeq ($(HARDWARE_MOTHERBOARD),73)
 # Geeetech GT2560 Rev. A
 else ifeq ($(HARDWARE_MOTHERBOARD),74)
 # Geeetech GT2560 Rev. A+ (with auto level probe)
 else ifeq ($(HARDWARE_MOTHERBOARD),75)
+# Geeetech GT2560 Rev B for A10(M/D)
+else ifeq ($(HARDWARE_MOTHERBOARD),76)
+# Geeetech GT2560 Rev B for A20(M/D)
+else ifeq ($(HARDWARE_MOTHERBOARD),86)
 
 #
 # ATmega1281, ATmega2561

Marlin/src/core/boards.h

 #define BOARD_GT2560_REV_A_PLUS 75    // Geeetech GT2560 Rev. A+ (with auto level probe)
 #define BOARD_GT2560_V3         76    // Geeetech GT2560 Rev B for A10(M/D)
 #define BOARD_GT2560_V3_MC2     73    // Geeetech GT2560 Rev B for Mecreator2
+#define BOARD_GT2560_V3_A20     86    // Geeetech GT2560 Rev B for A20(M/D)
 #define BOARD_EINSTART_S        666   // Einstart retrofit
 
 //

Marlin/src/pins/pins.h

   #include "pins_GT2560_V3.h"         // ATmega2560                                 env:megaatmega2560
 #elif MB(GT2560_V3_MC2)
   #include "pins_GT2560_V3_MC2.h"     // ATmega2560                                 env:megaatmega2560
+#elif MB(GT2560_V3_A20)
+  #include "pins_GT2560_V3_A20.h"     // ATmega2560                                 env:megaatmega2560
 #elif MB(EINSTART_S)
   #include "pins_EINSTART-S.h"        // ATmega1280, ATmega2560                     env:megaatmega1280 env:megaatmega2560
 

Marlin/src/pins/pins_GT2560_V3.h

 #endif
 
 //
+// Servos
+//
+#define SERVO0_PIN         11   //13 untested  3Dtouch
+
+//
 // Limit Switches
 //
 #define X_MIN_PIN          24
 #define LED_PIN             6
 #define PS_ON_PIN          12
 #define SUICIDE_PIN        54   //PIN that has to be turned on right after start, to keep power flowing.
-#define SERVO0_PIN         11   //13 untested  3Dtouch
 
 #ifndef CASE_LIGHT_PIN
   //#define CASE_LIGHT_PIN 21

Marlin/src/pins/pins_GT2560_V3_A20.h

+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Based on Sprinter and grbl.
+ * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/**
+ * Geeetech A20M pin assignment
+ */
+
+#include "pins_GT2560_V3.h"
+
+#undef LCD_PINS_RS
+#undef LCD_PINS_ENABLE
+#undef LCD_PINS_D4
+#undef LCD_PINS_D7
+#define LCD_PINS_RS       5
+#define LCD_PINS_ENABLE  36
+#define LCD_PINS_D4      21
+#define LCD_PINS_D7       6
+
+#if ENABLED(NEWPANEL)
+  #undef BTN_EN1
+  #undef BTN_EN2
+  #undef BTN_ENC
+  #define BTN_EN1        16
+  #define BTN_EN2        17
+  #define BTN_ENC        19
+#endif