Support SMART RAMPS 1.4 with Mega2560 (#21059)

Marlin/src/pins/sam/pins_RAMPS_SMART.h

@@ -60,8 +60,8 @@
  * (Search the web for "Arduino DUE Board Pinout" to see the correct header.)
  */
 
-#if NOT_TARGET(__SAM3X8E__)
-  #error "Oops! Select 'Arduino Due' in 'Tools > Board.'"
+#if NOT_TARGET(__SAM3X8E__, __AVR_ATmega2560__)
+  #error "Oops! Select 'Arduino Due' or 'Mega 2560' in 'Tools > Board.'"
 #endif
 
 #define BOARD_INFO_NAME "RAMPS-SMART"
@@ -72,6 +72,18 @@
 #define I2C_EEPROM
 #define MARLIN_EEPROM_SIZE                0x1000
 
+#define SDA_PIN                               20
+#define SCL_PIN                               21
+
+// See EEPROM device datasheet for the following values. These are for 24xx256
+#define EEPROM_SERIAL_ADDR                  0x50  // 7 bit i2c address (without R/W bit)
+#define EEPROM_PAGE_SIZE                      64  // page write buffer size
+#define EEPROM_PAGE_WRITE_TIME                 7  // page write time in milliseconds (docs say 5ms but that is too short)
+
+#define TWI_CLOCK_FREQ                    400000
+#define EEPROM_ADDRSZ_BYTES TWI_MMR_IADRSZ_2_BYTE // TWI_MMR_IADRSZ_1_BYTE for 1 byte, or TWI_MMR_IADRSZ_2_BYTE for 2 byte
+#define EEPROM_AVAILABLE              EEPROM_I2C
+
 #define RESET_PIN                             42  // Resets the board if the jumper is attached
 
 //
@@ -97,6 +109,7 @@
 //
 // LCD / Controller
 //
+
 // Support for AZSMZ 12864 LCD with SD Card 3D printer smart controller control panel
 #if ENABLED(AZSMZ_12864)
   #define BEEPER_PIN                          66  // Smart RAMPS 1.42 pinout diagram on RepRap WIKI erroneously says this should be pin 65