Z Axis Safe Homing when using Z Probe

Recommended for those who are using the Z Probe for Z Homing (as
Z-Endstop)

This feature has two changes:

1) Allow user to choose where the Z Probe will touch the bed when homing
all axis together (G28) by setting below defines:

Z_SAFE_HOMING_X_POINT
Z_SAFE_HOMING_Y_POINT

2) Prevents the user to perform Z Axis Homing when the Z Probe is
outsite bed.

Marlin/Configuration.h

 #define min_software_endstops true // If true, axis won't move to coordinates less than HOME_POS.
 #define max_software_endstops true  // If true, axis won't move to coordinates greater than the defined lengths below.
 
+// Travel limits after homing
+#define X_MAX_POS 205
+#define X_MIN_POS 0
+#define Y_MAX_POS 205
+#define Y_MIN_POS 0
+#define Z_MAX_POS 200
+#define Z_MIN_POS 0
+
+#define X_MAX_LENGTH (X_MAX_POS - X_MIN_POS)
+#define Y_MAX_LENGTH (Y_MAX_POS - Y_MIN_POS)
+#define Z_MAX_LENGTH (Z_MAX_POS - Z_MIN_POS)
 //============================= Bed Auto Leveling ===========================
 
 //#define ENABLE_AUTO_BED_LEVELING // Delete the comment to enable (remove // at the start of the line)
   // You MUST HAVE the SERVO_ENDSTOPS defined to use here a value higher than zero otherwise your code will not compile.
 
 //  #define PROBE_SERVO_DEACTIVATION_DELAY 300  
+
+
+//If you have enabled the Bed Auto Levelling and are using the same Z Probe for Z Homing, 
+//it is highly recommended you let this Z_SAFE_HOMING enabled!!!
+
+  #define Z_SAFE_HOMING   // This feature is meant to avoid Z homing with probe outside the bed area. 
+                          // When defined, it will:
+                          // - Allow Z homing only after X and Y homing AND stepper drivers still enabled
+                          // - If stepper drivers timeout, it will need X and Y homing again before Z homing
+                          // - Position the probe in a defined XY point before Z Homing when homing all axis (G28)
+                          // - Block Z homing only when the probe is outside bed area.
+  
+  #ifdef Z_SAFE_HOMING
+    
+    #define Z_SAFE_HOMING_X_POINT (X_MAX_LENGTH/2)    // X point for Z homing when homing all axis (G28)
+    #define Z_SAFE_HOMING_Y_POINT (Y_MAX_LENGTH/2)    // Y point for Z homing when homing all axis (G28)
+    
+  #endif
   
 #endif
 
-// Travel limits after homing
-#define X_MAX_POS 205
-#define X_MIN_POS 0
-#define Y_MAX_POS 205
-#define Y_MIN_POS 0
-#define Z_MAX_POS 200
-#define Z_MIN_POS 0
-
-#define X_MAX_LENGTH (X_MAX_POS - X_MIN_POS)
-#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
 //#define MANUAL_HOME_POSITIONS  // If defined, MANUAL_*_HOME_POS below will be used

Marlin/Marlin.h

 #if defined(DUAL_X_CARRIAGE) && defined(X_ENABLE_PIN) && X_ENABLE_PIN > -1 \
     && defined(X2_ENABLE_PIN) && X2_ENABLE_PIN > -1
   #define  enable_x() do { WRITE(X_ENABLE_PIN, X_ENABLE_ON); WRITE(X2_ENABLE_PIN, X_ENABLE_ON); } while (0)
-  #define disable_x() do { WRITE(X_ENABLE_PIN,!X_ENABLE_ON); WRITE(X2_ENABLE_PIN,!X_ENABLE_ON); } while (0)
+  #define disable_x() do { WRITE(X_ENABLE_PIN,!X_ENABLE_ON); WRITE(X2_ENABLE_PIN,!X_ENABLE_ON); axis_known_position[X_AXIS] = false; } while (0)
 #elif defined(X_ENABLE_PIN) && X_ENABLE_PIN > -1
   #define  enable_x() WRITE(X_ENABLE_PIN, X_ENABLE_ON)
-  #define disable_x() WRITE(X_ENABLE_PIN,!X_ENABLE_ON)
+  #define disable_x() { WRITE(X_ENABLE_PIN,!X_ENABLE_ON); axis_known_position[X_AXIS] = false; }
 #else
   #define enable_x() ;
   #define disable_x() ;
 #if defined(Y_ENABLE_PIN) && Y_ENABLE_PIN > -1
   #ifdef Y_DUAL_STEPPER_DRIVERS
     #define  enable_y() { WRITE(Y_ENABLE_PIN, Y_ENABLE_ON); WRITE(Y2_ENABLE_PIN,  Y_ENABLE_ON); }
-    #define disable_y() { WRITE(Y_ENABLE_PIN,!Y_ENABLE_ON); WRITE(Y2_ENABLE_PIN, !Y_ENABLE_ON); }
+    #define disable_y() { WRITE(Y_ENABLE_PIN,!Y_ENABLE_ON); WRITE(Y2_ENABLE_PIN, !Y_ENABLE_ON); axis_known_position[Y_AXIS] = false; }
   #else
     #define  enable_y() WRITE(Y_ENABLE_PIN, Y_ENABLE_ON)
-    #define disable_y() WRITE(Y_ENABLE_PIN,!Y_ENABLE_ON)
+    #define disable_y() { WRITE(Y_ENABLE_PIN,!Y_ENABLE_ON); axis_known_position[Y_AXIS] = false; }
   #endif
 #else
   #define enable_y() ;
 #if defined(Z_ENABLE_PIN) && Z_ENABLE_PIN > -1
   #ifdef Z_DUAL_STEPPER_DRIVERS
     #define  enable_z() { WRITE(Z_ENABLE_PIN, Z_ENABLE_ON); WRITE(Z2_ENABLE_PIN, Z_ENABLE_ON); }
-    #define disable_z() { WRITE(Z_ENABLE_PIN,!Z_ENABLE_ON); WRITE(Z2_ENABLE_PIN,!Z_ENABLE_ON); }
+    #define disable_z() { WRITE(Z_ENABLE_PIN,!Z_ENABLE_ON); WRITE(Z2_ENABLE_PIN,!Z_ENABLE_ON); axis_known_position[Z_AXIS] = false; }
   #else
     #define  enable_z() WRITE(Z_ENABLE_PIN, Z_ENABLE_ON)
-    #define disable_z() WRITE(Z_ENABLE_PIN,!Z_ENABLE_ON)
+    #define disable_z() { WRITE(Z_ENABLE_PIN,!Z_ENABLE_ON); axis_known_position[Z_AXIS] = false; }
   #endif
 #else
   #define enable_z() ;
 #endif
 extern float min_pos[3];
 extern float max_pos[3];
+extern bool axis_known_position[3];
 extern int fanSpeed;
 #ifdef BARICUDA
 extern int ValvePressure;

Marlin/Marlin_main.cpp

 #include "ConfigurationStore.h"
 #include "language.h"
 #include "pins_arduino.h"
+#include "math.h"
 
 #ifdef BLINKM
 #include "BlinkM.h"
 #endif
 float min_pos[3] = { X_MIN_POS, Y_MIN_POS, Z_MIN_POS };
 float max_pos[3] = { X_MAX_POS, Y_MAX_POS, Z_MAX_POS };
+bool axis_known_position[3] = {false, false, false};
 
 // Extruder offset
 #if EXTRUDERS > 1
     current_position[axis] = 0;
     plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
 	
+
     // Engage Servo endstop if enabled
     #ifdef SERVO_ENDSTOPS
       #if defined (ENABLE_AUTO_BED_LEVELING) && (PROBE_SERVO_DEACTIVATION_DELAY > 0)
         if (axis==Z_AXIS) {
-          #if defined (Z_RAISE_BEFORE_HOMING) && (Z_RAISE_BEFORE_HOMING > 0)
-            destination[axis] = Z_RAISE_BEFORE_HOMING * axis_home_dir * (-1);    // Set destination away from bed
-            feedrate = max_feedrate[axis];
-            plan_buffer_line(destination[X_AXIS], destination[Y_AXIS], destination[Z_AXIS], destination[E_AXIS], feedrate, active_extruder);
-            st_synchronize();
-          #endif
           engage_z_probe();
         }
 	    else
     destination[axis] = current_position[axis];
     feedrate = 0.0;
     endstops_hit_on_purpose();
+    axis_known_position[axis] = true;
 
     // Retract Servo endstop if enabled
     #ifdef SERVO_ENDSTOPS
         HOMEAXIS(Y);
       }
 
-      #if Z_HOME_DIR < 0                      // If homing towards BED do Z last
-      if((home_all_axis) || (code_seen(axis_codes[Z_AXIS]))) {
-        HOMEAXIS(Z);
-      }
-      #endif
-
       if(code_seen(axis_codes[X_AXIS]))
       {
         if(code_value_long() != 0) {
           current_position[Y_AXIS]=code_value()+add_homeing[1];
         }
       }
+      
+      #if Z_HOME_DIR < 0                      // If homing towards BED do Z last
+        #ifndef Z_SAFE_HOMING
+          if((home_all_axis) || (code_seen(axis_codes[Z_AXIS]))) {
+            #if defined (Z_RAISE_BEFORE_HOMING) && (Z_RAISE_BEFORE_HOMING > 0)
+              destination[Z_AXIS] = Z_RAISE_BEFORE_HOMING * home_dir(Z_AXIS) * (-1);    // Set destination away from bed
+              feedrate = max_feedrate[Z_AXIS];
+              plan_buffer_line(destination[X_AXIS], destination[Y_AXIS], destination[Z_AXIS], destination[E_AXIS], feedrate, active_extruder);
+              st_synchronize();
+            #endif
+            HOMEAXIS(Z);
+          }
+        #else                      // Z Safe mode activated. 
+          if(home_all_axis) {
+            destination[X_AXIS] = round(Z_SAFE_HOMING_X_POINT - X_PROBE_OFFSET_FROM_EXTRUDER);
+            destination[Y_AXIS] = round(Z_SAFE_HOMING_Y_POINT - Y_PROBE_OFFSET_FROM_EXTRUDER);
+            destination[Z_AXIS] = Z_RAISE_BEFORE_HOMING * home_dir(Z_AXIS) * (-1);    // Set destination away from bed
+            feedrate = XY_TRAVEL_SPEED;
+            current_position[Z_AXIS] = 0;
+			
+            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
+            plan_buffer_line(destination[X_AXIS], destination[Y_AXIS], destination[Z_AXIS], destination[E_AXIS], feedrate, active_extruder);
+            st_synchronize();
+            current_position[X_AXIS] = destination[X_AXIS];
+            current_position[Y_AXIS] = destination[Y_AXIS];
 
+            HOMEAXIS(Z);
+          }
+                                                // Let's see if X and Y are homed and probe is inside bed area.
+          if(code_seen(axis_codes[Z_AXIS])) {
+            if ( (axis_known_position[X_AXIS]) && (axis_known_position[Y_AXIS]) \
+              && (current_position[X_AXIS]+X_PROBE_OFFSET_FROM_EXTRUDER >= X_MIN_POS) \
+              && (current_position[X_AXIS]+X_PROBE_OFFSET_FROM_EXTRUDER <= X_MAX_POS) \
+              && (current_position[Y_AXIS]+Y_PROBE_OFFSET_FROM_EXTRUDER >= Y_MIN_POS) \
+              && (current_position[Y_AXIS]+Y_PROBE_OFFSET_FROM_EXTRUDER <= Y_MAX_POS)) {
+
+              current_position[Z_AXIS] = 0;
+              plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);			  
+              destination[Z_AXIS] = Z_RAISE_BEFORE_HOMING * home_dir(Z_AXIS) * (-1);    // Set destination away from bed
+              feedrate = max_feedrate[Z_AXIS];
+              plan_buffer_line(destination[X_AXIS], destination[Y_AXIS], destination[Z_AXIS], destination[E_AXIS], feedrate, active_extruder);
+              st_synchronize();
+
+              HOMEAXIS(Z);
+            } else if (!((axis_known_position[X_AXIS]) && (axis_known_position[Y_AXIS]))) {
+                LCD_MESSAGEPGM(MSG_POSITION_UNKNOWN);
+                SERIAL_ECHO_START;
+                SERIAL_ECHOLNPGM(MSG_POSITION_UNKNOWN);
+            } else {
+                LCD_MESSAGEPGM(MSG_ZPROBE_OUT);
+                SERIAL_ECHO_START;
+                SERIAL_ECHOLNPGM(MSG_ZPROBE_OUT);
+            }
+          }
+        #endif
+      #endif
+
+      
+     
       if(code_seen(axis_codes[Z_AXIS])) {
         if(code_value_long() != 0) {
           current_position[Z_AXIS]=code_value()+add_homeing[2];
         }
       }
       #ifdef ENABLE_AUTO_BED_LEVELING
-         current_position[Z_AXIS] -= Z_PROBE_OFFSET_FROM_EXTRUDER;  //Add Z_Probe offset (the distance is negative)
+        if((home_all_axis) || (code_seen(axis_codes[Z_AXIS]))) {
+          current_position[Z_AXIS] -= Z_PROBE_OFFSET_FROM_EXTRUDER;  //Add Z_Probe offset (the distance is negative)
+        }
       #endif
       plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
 #endif // else DELTA
             do_blocking_move_to(LEFT_PROBE_BED_POSITION - X_PROBE_OFFSET_FROM_EXTRUDER, BACK_PROBE_BED_POSITION - Y_PROBE_OFFSET_FROM_EXTRUDER, current_position[Z_AXIS]);
 
             engage_z_probe();   // Engage Z Servo endstop if available
-            
             run_z_probe();
             float z_at_xLeft_yBack = current_position[Z_AXIS];
+            retract_z_probe();
 
             SERIAL_PROTOCOLPGM("Bed x: ");
             SERIAL_PROTOCOL(LEFT_PROBE_BED_POSITION);
             // prob 2
             do_blocking_move_to(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS] + Z_RAISE_BETWEEN_PROBINGS);
             do_blocking_move_to(LEFT_PROBE_BED_POSITION - X_PROBE_OFFSET_FROM_EXTRUDER, FRONT_PROBE_BED_POSITION - Y_PROBE_OFFSET_FROM_EXTRUDER, current_position[Z_AXIS]);
+
+            engage_z_probe();   // Engage Z Servo endstop if available
             run_z_probe();
             float z_at_xLeft_yFront = current_position[Z_AXIS];
-
+            retract_z_probe();
+            
             SERIAL_PROTOCOLPGM("Bed x: ");
             SERIAL_PROTOCOL(LEFT_PROBE_BED_POSITION);
             SERIAL_PROTOCOLPGM(" y: ");
             do_blocking_move_to(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS] + Z_RAISE_BETWEEN_PROBINGS);
             // the current position will be updated by the blocking move so the head will not lower on this next call.
             do_blocking_move_to(RIGHT_PROBE_BED_POSITION - X_PROBE_OFFSET_FROM_EXTRUDER, FRONT_PROBE_BED_POSITION - Y_PROBE_OFFSET_FROM_EXTRUDER, current_position[Z_AXIS]);
+
+            engage_z_probe();   // Engage Z Servo endstop if available
             run_z_probe();
             float z_at_xRight_yFront = current_position[Z_AXIS];
-
+            retract_z_probe(); // Retract Z Servo endstop if available
+            
             SERIAL_PROTOCOLPGM("Bed x: ");
             SERIAL_PROTOCOL(RIGHT_PROBE_BED_POSITION);
             SERIAL_PROTOCOLPGM(" y: ");
 
             set_bed_level_equation(z_at_xLeft_yFront, z_at_xRight_yFront, z_at_xLeft_yBack);
 
-            retract_z_probe(); // Retract Z Servo endstop if available
-            
             st_synchronize();            
 
             // The following code correct the Z height difference from z-probe position and hotend tip position.

Marlin/language.h

 	#define MSG_FILAMENTCHANGE "Change filament"
 	#define MSG_INIT_SDCARD "Init. SD-Card"	
 	#define MSG_CNG_SDCARD "Change SD-Card"
+    #define MSG_ZPROBE_OUT "ZProbe Outside Bed"
+    #define MSG_POSITION_UNKNOWN "Home X/Y before Z"
 
 // Serial Console Messages
 
 	#define MSG_FILAMENTCHANGE "Change filament"
 	#define MSG_INIT_SDCARD "Init. SD-Card"	
 	#define MSG_CNG_SDCARD "Change SD-Card"
+    #define MSG_ZPROBE_OUT "ZProbe Outside Bed"
+    #define MSG_POSITION_UNKNOWN "Home X/Y before Z"
 
 // Serial Console Messages
 
 	#define MSG_FILAMENTCHANGE "Changer filament"
 	#define MSG_INIT_SDCARD "Init. la carte SD"	
 	#define MSG_CNG_SDCARD "Changer de carte SD"
+    #define MSG_ZPROBE_OUT "ZProbe Outside Bed"
+    #define MSG_POSITION_UNKNOWN "Home X/Y before Z"
 
 // Serial Console Messages
 
 	#define MSG_FILAMENTCHANGE "Filament wechseln"
 	#define MSG_INIT_SDCARD "Init. SD-Card"	
 	#define MSG_CNG_SDCARD "Change SD-Card"
+    #define MSG_ZPROBE_OUT "ZProbe Outside Bed"
+    #define MSG_POSITION_UNKNOWN "Home X/Y before Z"
 	
 // Serial Console Messages
 
 	#define MSG_RETRACT_ARROW "Retraer"
 	#define MSG_PART_RELEASE "Desacople Parcial"
 	#define MSG_STEPPER_RELEASED "Desacoplada."
+    #define MSG_ZPROBE_OUT "ZProbe Outside Bed"
+    #define MSG_POSITION_UNKNOWN "Home X/Y before Z"
 
 // Serial Console Messages
 
 	#define MSG_FILAMENTCHANGE "Change filament"
 	#define MSG_INIT_SDCARD "Init. SD-Card"	
 	#define MSG_CNG_SDCARD "Change SD-Card"
+    #define MSG_ZPROBE_OUT "ZProbe Outside Bed"
+    #define MSG_POSITION_UNKNOWN "Home X/Y before Z"
 
 // Serial Console Messages
 
 	#define MSG_FILAMENTCHANGE       "Cambia filamento"
 	#define MSG_INIT_SDCARD          "Iniz. SD-Card"
 	#define MSG_CNG_SDCARD           "Cambia SD-Card"
+    #define MSG_ZPROBE_OUT "ZProbe Outside Bed"
+    #define MSG_POSITION_UNKNOWN "Home X/Y before Z"
 
 	// Serial Console Messages
 
 	#define MSG_FILAMENTCHANGE "Change filament"
 	#define MSG_INIT_SDCARD "Init. SD-Card"	
 	#define MSG_CNG_SDCARD "Change SD-Card"
+    #define MSG_ZPROBE_OUT "Sonda fora da mesa"
+    #define MSG_POSITION_UNKNOWN "Home X/Y antes de Z"
 
 // Serial Console Messages
 
 	#define MSG_FILAMENTCHANGE "Change filament"
 	#define MSG_INIT_SDCARD "Init. SD-Card"	
 	#define MSG_CNG_SDCARD "Change SD-Card"
+    #define MSG_ZPROBE_OUT "ZProbe Outside Bed"
+    #define MSG_POSITION_UNKNOWN "Home X/Y before Z"
 
 // Serial Console Messages