fixes #246

Added statements to set the limit switch positions to the maximum travel if homing in the positive direction as well as bed center at (0,0) if defined.

Marlin/Configuration.h

@@ -203,10 +203,56 @@ const bool Z_ENDSTOPS_INVERTING = true; // set to true to invert the logic of th
 #define Y_MAX_LENGTH (Y_MAX_POS - Y_MIN_POS)
 #define Z_MAX_LENGTH (Z_MAX_POS - Z_MIN_POS)
 
-// The position of the homing switches. Use MAX_LENGTH * -0.5 if the center should be 0, 0, 0
-#define X_HOME_POS 0
-#define Y_HOME_POS 0
-#define Z_HOME_POS 0
+// The position of the homing switches
+// Auto switch code by ZetaPhoenix
+//#define MANUAL_HOME_POSITIONS  //If defined, manualy programed locations will be loaded
+//#define BED_CENTER_AT_0_0
+
+#ifdef MANUAL_HOME_POSITION  //Manual limit switch locations
+  #define X_HOME_POS 0
+  #define Y_HOME_POS 0
+  #define Z_HOME_POS 0
+
+//Set min/max homing switch positions based upon direction and min/max travel limits
+#else
+  //X axis
+  #if X_HOME_DIR == -1
+    #ifdef BED_CENTER_AT_0_0
+      #define X_HOME_POS X_MAX_LENGTH * -0.5
+    #else
+      #define X_HOME_POS X_MIN_POS
+    #endif //BED_CENTER_AT_0_0
+  #else    
+    #ifdef BED_CENTER_AT_0_0
+      #define X_HOME_POS X_MAX_LENGTH * 0.5
+    #else
+      #define X_HOME_POS X_MAX_POS
+    #endif //BED_CENTER_AT_0_0
+  #endif //X_HOME_DIR == -1
+  
+  //Y axis
+  #if Y_HOME_DIR == -1
+    #ifdef BED_CENTER_AT_0_0
+      #define Y_HOME_POS Y_MAX_LENGTH * -0.5
+    #else
+      #define Y_HOME_POS Y_MIN_POS
+    #endif //BED_CENTER_AT_0_0
+  #else    
+    #ifdef BED_CENTER_AT_0_0
+      #define Y_HOME_POS Y_MAX_LENGTH * 0.5
+    #else
+      #define Y_HOME_POS Y_MAX_POS
+    #endif //BED_CENTER_AT_0_0
+  #endif //Y_HOME_DIR == -1
+  
+  // Z axis
+  #if Z_HOME_DIR == -1 //BED_CENTER_AT_0_0 not used
+    #define Z_HOME_POS Z_MIN_POS
+  #else    
+    #define Z_HOME_POS Z_MAX_POS
+  #endif //Z_HOME_DIR == -1
+#endif //End auto min/max positions
+
 
 //// MOVEMENT SETTINGS
 #define NUM_AXIS 4 // The axis order in all axis related arrays is X, Y, Z, E