Ported over Johann Rocholl's improvements for delta printers:

- Nonlinear auto bed leveling code (includes G29, G30, Z_RAISE_AFTER_PROBING). Cleaned it up to be a delta-specific AUTO_BED_LEVELING_GRID code path.
- Allen key z-probe deployment and retraction code. Cleaned it up and added safety checks.

Marlin/example_configurations/delta/Configuration.h

@@ -110,6 +110,9 @@ Here are some standard links for getting your machine calibrated:
 // Effective horizontal distance bridged by diagonal push rods.
 #define DELTA_RADIUS (DELTA_SMOOTH_ROD_OFFSET-DELTA_EFFECTOR_OFFSET-DELTA_CARRIAGE_OFFSET)
 
+// Print surface diameter/2 minus unreachable space (avoid collisions with vertical towers).
+#define DELTA_PRINTABLE_RADIUS 90
+
 
 //===========================================================================
 //============================= Thermal Settings ============================
@@ -361,8 +364,7 @@ const bool X_MAX_ENDSTOP_INVERTING = true; // set to true to invert the logic of
 const bool Y_MAX_ENDSTOP_INVERTING = true; // set to true to invert the logic of the endstop.
 const bool Z_MAX_ENDSTOP_INVERTING = true; // set to true to invert the logic of the endstop.
 //#define DISABLE_MAX_ENDSTOPS
-// Deltas never have min endstops
-#define DISABLE_MIN_ENDSTOPS
+#define DISABLE_MIN_ENDSTOPS // Deltas only use min endstops for probing
 
 // For Inverting Stepper Enable Pins (Active Low) use 0, Non Inverting (Active High) use 1
 #define X_ENABLE_ON 0
@@ -413,8 +415,80 @@ const bool Z_MAX_ENDSTOP_INVERTING = true; // set to true to invert the logic of
 //============================= Bed Auto Leveling ===========================
 //===========================================================================
 
-//Bed Auto Leveling is still not compatible with Delta Kinematics
+//#define ENABLE_AUTO_BED_LEVELING // Delete the comment to enable (remove // at the start of the line)
+// Z-Probe Repeatability test is not supported in Deltas yet.
 
+#ifdef ENABLE_AUTO_BED_LEVELING
+
+  // Deltas only support grid mode
+  #define AUTO_BED_LEVELING_GRID
+
+  #define DELTA_PROBABLE_RADIUS (DELTA_PRINTABLE_RADIUS - 10)
+  #define LEFT_PROBE_BED_POSITION -DELTA_PROBABLE_RADIUS
+  #define RIGHT_PROBE_BED_POSITION DELTA_PROBABLE_RADIUS
+  #define BACK_PROBE_BED_POSITION DELTA_PROBABLE_RADIUS
+  #define FRONT_PROBE_BED_POSITION -DELTA_PROBABLE_RADIUS   
+
+  // Non-linear bed leveling will be used.
+  // Compensate by interpolating between the nearest four Z probe values for each point.
+  // Useful for deltas where the print surface may appear like a bowl or dome shape.
+  // Works best with ACCURATE_BED_LEVELING_POINTS 5 or higher.
+  #define AUTO_BED_LEVELING_GRID_POINTS 9
+
+  // Offsets to the probe relative to the extruder tip (Hotend - Probe)
+  // X and Y offsets must be integers
+  #define X_PROBE_OFFSET_FROM_EXTRUDER 0     // -left  +right
+  #define Y_PROBE_OFFSET_FROM_EXTRUDER -10   // -front +behind
+  #define Z_PROBE_OFFSET_FROM_EXTRUDER -3.5  // -below (always!)
+
+  #define Z_RAISE_BEFORE_HOMING 4       // (in mm) Raise Z before homing (G28) for Probe Clearance.
+                                        // Be sure you have this distance over your Z_MAX_POS in case
+
+  #define XY_TRAVEL_SPEED 4000         // X and Y axis travel speed between probes, in mm/min
+
+  #define Z_RAISE_BEFORE_PROBING 15   //How much the extruder will be raised before traveling to the first probing point.
+  #define Z_RAISE_BETWEEN_PROBINGS 5  //How much the extruder will be raised when traveling from between next probing points
+  #define Z_RAISE_AFTER_PROBING 50    //How much the extruder will be raised after the last probing point.
+  
+  // Allen key retractable z-probe as seen on many Kossel delta printers - http://reprap.org/wiki/Kossel#Automatic_bed_leveling_probe
+  // Deploys by touching z-axis belt. Retracts by pushing the probe down. Uses Z_MIN_PIN.
+  //#define Z_PROBE_ALLEN_KEY
+  #ifdef Z_PROBE_ALLEN_KEY
+    #define Z_PROBE_ALLEN_KEY_DEPLOY_X 30
+    #define Z_PROBE_ALLEN_KEY_DEPLOY_Y DELTA_PRINTABLE_RADIUS
+    #define Z_PROBE_ALLEN_KEY_DEPLOY_Z 100
+    
+    #define Z_PROBE_ALLEN_KEY_RETRACT_X     -64
+    #define Z_PROBE_ALLEN_KEY_RETRACT_Y     56
+    #define Z_PROBE_ALLEN_KEY_RETRACT_Z     23
+    #define Z_PROBE_ALLEN_KEY_RETRACT_DEPTH 20
+  #endif
+  
+  //If defined, the Probe servo will be turned on only during movement and then turned off to avoid jerk
+  //The value is the delay to turn the servo off after powered on - depends on the servo speed; 300ms is good value, but you can try lower it.
+  // 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 Leveling 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 // ENABLE_AUTO_BED_LEVELING
 
 
 

Marlin/example_configurations/delta/Configuration_adv.h

@@ -455,9 +455,27 @@ const unsigned int dropsegments=5; //everything with less than this number of st
 //===========================================================================
 
 #if defined (ENABLE_AUTO_BED_LEVELING) && defined (DELTA)
-  #error "Bed Auto Leveling is still not compatible with Delta Kinematics."
+
+  #if not defined(AUTO_BED_LEVELING_GRID)
+    #error "Only Grid Bed Auto Leveling is supported on Deltas."
+  #endif
+  
+  #if defined(Z_PROBE_SLED)
+    #error "You cannot use Z_PROBE_SLED together with DELTA."
+  #endif
+
+  #if defined(Z_PROBE_REPEATABILITY_TEST)
+    #error "Z-probe repeatability test is not supported on Deltas yet."
+  #endif
+
 #endif  
 
+#if defined(Z_PROBE_ALLEN_KEY)
+  #if !defined(AUTO_BED_LEVELING_GRID) || !defined(DELTA)
+    #error "Invalid use of Z_PROBE_ALLEN_KEY."
+  #endif
+#endif
+
 #if EXTRUDERS > 1 && defined TEMP_SENSOR_1_AS_REDUNDANT
   #error "You cannot use TEMP_SENSOR_1_AS_REDUNDANT if EXTRUDERS > 1"
 #endif