sled improvements

- create sled pin definition
- G28 Works with sled

Marlin/Conditionals.h

@@ -276,6 +276,13 @@
     #define MAX_PROBE_Y (min(Y_MAX_POS, Y_MAX_POS + Y_PROBE_OFFSET_FROM_EXTRUDER))
   #endif
 
+   /**
+    * Sled Options
+    */ 
+  #ifdef Z_PROBE_SLED
+    #define Z_SAFE_HOMING
+  #endif
+  
   /**
    * MAX_STEP_FREQUENCY differs for TOSHIBA
    */

Marlin/Marlin_main.cpp

@@ -650,8 +650,8 @@ void setup() {
   #endif
 
   #ifdef Z_PROBE_SLED
-    pinMode(SERVO0_PIN, OUTPUT);
+    pinMode(SLED_PIN, OUTPUT);
-    digitalWrite(SERVO0_PIN, LOW); // turn it off
+    digitalWrite(SLED_PIN, LOW); // turn it off
   #endif // Z_PROBE_SLED
 
   setup_homepin();
@@ -1516,6 +1516,48 @@ inline void set_destination_to_current() { memcpy(destination, current_position,
 
 #endif // ENABLE_AUTO_BED_LEVELING
 
+
+#ifdef Z_PROBE_SLED
+
+  #ifndef SLED_DOCKING_OFFSET
+    #define SLED_DOCKING_OFFSET 0
+  #endif
+
+  /**
+   * Method to dock/undock a sled designed by Charles Bell.
+   *
+   * dock[in]     If true, move to MAX_X and engage the electromagnet
+   * offset[in]   The additional distance to move to adjust docking location
+   */
+  static void dock_sled(bool dock, int offset=0) {
+    if (!axis_known_position[X_AXIS] || !axis_known_position[Y_AXIS]) {
+      LCD_MESSAGEPGM(MSG_POSITION_UNKNOWN);
+      SERIAL_ECHO_START;
+      SERIAL_ECHOLNPGM(MSG_POSITION_UNKNOWN);
+      return;
+    }
+
+    if (dock) {
+      float oldXpos = current_position[X_AXIS]; // save x position
+      do_blocking_move_to(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS] + Z_RAISE_AFTER_PROBING); // rise Z   
+      do_blocking_move_to(X_MAX_POS + SLED_DOCKING_OFFSET + offset - 1, current_position[Y_AXIS], current_position[Z_AXIS]);  // Dock sled a bit closer to ensure proper capturing                                                                                                                           
+      digitalWrite(SLED_PIN, LOW); // turn off magnet
+      do_blocking_move_to(oldXpos, current_position[Y_AXIS], current_position[Z_AXIS]); // return to position before docking
+      do_blocking_move_to(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS] - Z_RAISE_AFTER_PROBING);
+    } else {
+      float oldXpos = current_position[X_AXIS]; // save x position
+      float z_loc = current_position[Z_AXIS];
+      if (z_loc < Z_RAISE_BEFORE_PROBING + 5) z_loc = Z_RAISE_BEFORE_PROBING;
+      do_blocking_move_to(X_MAX_POS + SLED_DOCKING_OFFSET + offset, current_position[Y_AXIS], z_loc); // this also updates current_position
+      digitalWrite(SLED_PIN, HIGH); // turn on magnet
+      do_blocking_move_to(oldXpos, current_position[Y_AXIS], current_position[Z_AXIS]); // return to position before docking
+    }
+  }
+
+#endif // Z_PROBE_SLED
+
+
+
 /**
  * Home an individual axis
  */
@@ -1538,6 +1580,13 @@ static void homeaxis(AxisEnum axis) {
     current_position[axis] = 0;
     sync_plan_position();
 
+    #ifdef Z_PROBE_SLED
+      // Get Probe
+      if (axis == Z_AXIS) {
+        if (axis_home_dir < 0) dock_sled(false);
+      }
+    #endif
+    
     #if SERVO_LEVELING && !defined(Z_PROBE_SLED)
 
       // Deploy a probe if there is one, and homing towards the bed
@@ -1634,6 +1683,13 @@ static void homeaxis(AxisEnum axis) {
     endstops_hit_on_purpose(); // clear endstop hit flags
     axis_known_position[axis] = true;
 
+    #ifdef Z_PROBE_SLED
+    // bring probe back
+      if (axis == Z_AXIS) {
+        if (axis_home_dir < 0) dock_sled(true);
+      } 
+    #endif
+
     #if SERVO_LEVELING && !defined(Z_PROBE_SLED)
 
       // Deploy a probe if there is one, and homing towards the bed
@@ -1708,39 +1764,6 @@ static void homeaxis(AxisEnum axis) {
 
 #endif // FWRETRACT
 
-#ifdef Z_PROBE_SLED
-
-  #ifndef SLED_DOCKING_OFFSET
-    #define SLED_DOCKING_OFFSET 0
-  #endif
-
-  /**
-   * Method to dock/undock a sled designed by Charles Bell.
-   *
-   * dock[in]     If true, move to MAX_X and engage the electromagnet
-   * offset[in]   The additional distance to move to adjust docking location
-   */
-  static void dock_sled(bool dock, int offset=0) {
-    if (!axis_known_position[X_AXIS] || !axis_known_position[Y_AXIS]) {
-      LCD_MESSAGEPGM(MSG_POSITION_UNKNOWN);
-      SERIAL_ECHO_START;
-      SERIAL_ECHOLNPGM(MSG_POSITION_UNKNOWN);
-      return;
-    }
-
-    if (dock) {
-      do_blocking_move_to(X_MAX_POS + SLED_DOCKING_OFFSET + offset, current_position[Y_AXIS], current_position[Z_AXIS]); // this also updates current_position
-      digitalWrite(SERVO0_PIN, LOW); // turn off magnet
-    } else {
-      float z_loc = current_position[Z_AXIS];
-      if (z_loc < Z_RAISE_BEFORE_PROBING + 5) z_loc = Z_RAISE_BEFORE_PROBING;
-      do_blocking_move_to(X_MAX_POS + SLED_DOCKING_OFFSET + offset, Y_PROBE_OFFSET_FROM_EXTRUDER, z_loc); // this also updates current_position
-      digitalWrite(SERVO0_PIN, HIGH); // turn on magnet
-    }
-  }
-
-#endif // Z_PROBE_SLED
-
 /**
  *
  * G-Code Handler functions
@@ -2586,7 +2609,7 @@ inline void gcode_G28() {
     #endif // !DELTA
 
     #ifdef Z_PROBE_SLED
-      dock_sled(true, -SLED_DOCKING_OFFSET); // dock the probe, correcting for over-travel
+      dock_sled(true); // dock the probe
     #elif defined(Z_PROBE_ALLEN_KEY) //|| defined(SERVO_LEVELING)
       stow_z_probe();
     #endif

Marlin/pins_SANGUINOLOLU_11.h

@@ -44,6 +44,10 @@
   #define FAN_PIN            4
 #endif
 
+#ifdef Z_PROBE_SLED
+  #define SLED_PIN         27
+#endif
+
 #ifdef NUM_SERVOS
   #define SERVO0_PIN          -1