Increased the "calibration point not found" threshold from 0.5mm to 1.mm

difference from the reference value stored in the EEPROM.
Lowered the speed of lowering the Z axis during the XY calibration
from 0.5mm per zig-zag search to 0.2mm to avoid the nozzle scratching
the bed if the PINDA sensor is mounted too high.
Improved the display routine to break the interpunction from the end
of a sentence. While the result may not be typographically correct,
more fits onto the screen.

Firmware/Marlin_main.cpp

@@ -2382,7 +2382,7 @@ void process_commands()
                 st_synchronize();
                 
                 // Go down until endstop is hit
-                const float Z_CALIBRATION_THRESHOLD = 0.5f;
+                const float Z_CALIBRATION_THRESHOLD = 1.f;
                 if (! find_bed_induction_sensor_point_z((has_z && mesh_point > 0) ? z0 - Z_CALIBRATION_THRESHOLD : -10.f)) {
                     kill_message = MSG_BED_LEVELING_FAILED_POINT_LOW;
                     break;

Firmware/mesh_bed_calibration.cpp

@@ -749,7 +749,7 @@ error:
 #define FIND_BED_INDUCTION_SENSOR_POINT_X_RADIUS (8.f)
 #define FIND_BED_INDUCTION_SENSOR_POINT_Y_RADIUS (6.f)
 #define FIND_BED_INDUCTION_SENSOR_POINT_XY_STEP  (1.f)
-#define FIND_BED_INDUCTION_SENSOR_POINT_Z_STEP   (0.5f)
+#define FIND_BED_INDUCTION_SENSOR_POINT_Z_STEP   (0.2f)
 inline bool find_bed_induction_sensor_point_xy()
 {
     float feedrate = homing_feedrate[X_AXIS] / 60.f;
@@ -1039,6 +1039,7 @@ inline bool improve_bed_induction_sensor_point2(bool lift_z_on_min_y, int8_t ver
     float center_old_x = current_position[X_AXIS];
     float center_old_y = current_position[Y_AXIS];
     float a, b;
+    bool  point_small = false;
 
     enable_endstops(false);
 
@@ -1078,8 +1079,14 @@ inline bool improve_bed_induction_sensor_point2(bool lift_z_on_min_y, int8_t ver
                 SERIAL_ECHOLNPGM("");
             }
             // We force the calibration routine to move the Z axis slightly down to make the response more pronounced.
-            current_position[X_AXIS] = center_old_x;
-            goto canceled;            
+            if (b - a < 0.5f * MIN_BED_SENSOR_POINT_RESPONSE_DMR) {
+                // Don't use the new X value.
+                current_position[X_AXIS] = center_old_x;
+                goto canceled;
+            } else {
+                // Use the new value, but force the Z axis to go a bit lower.
+                point_small = true;
+            }
         }
         if (verbosity_level >= 5) {
             debug_output_point(PSTR("left" ), a, current_position[Y_AXIS], current_position[Z_AXIS]);
@@ -1142,8 +1149,14 @@ inline bool improve_bed_induction_sensor_point2(bool lift_z_on_min_y, int8_t ver
                 SERIAL_ECHO(b - a);
                 SERIAL_ECHOLNPGM("");
             }
-            current_position[Y_AXIS] = center_old_y;
-            goto canceled;
+            if (b - a < 0.5f * MIN_BED_SENSOR_POINT_RESPONSE_DMR) {
+                // Don't use the new Y value.
+                current_position[Y_AXIS] = center_old_y;
+                goto canceled;
+            } else {
+                // Use the new value, but force the Z axis to go a bit lower.
+                point_small = true;
+            }
         }
         if (verbosity_level >= 5) {
             debug_output_point(PSTR("top" ), current_position[X_AXIS], a, current_position[Z_AXIS]);
@@ -1156,7 +1169,11 @@ inline bool improve_bed_induction_sensor_point2(bool lift_z_on_min_y, int8_t ver
         go_xy(current_position[X_AXIS], current_position[Y_AXIS], homing_feedrate[X_AXIS] / 60.f);
     }
 
-    return true;
+    // If point is small but not too small, then force the Z axis to be lowered a bit,
+    // but use the new value. This is important when the initial position was off in one axis,
+    // for example if the initial calibration was shifted in the Y axis systematically.
+    // Then this first step will center.
+    return ! point_small;
 
 canceled:
     // Go back to the center.

Firmware/ultralcd.cpp

@@ -1370,12 +1370,18 @@ static inline bool pgm_is_whitespace(const char *c)
     return pgm_read_byte(c) == ' ' || pgm_read_byte(c) == '\t' || pgm_read_byte(c) == '\r' || pgm_read_byte(c) == '\n';
 }
 
-void lcd_display_message_fullscreen_P(const char *msg)
+static inline bool pgm_is_interpunction(const char *c)
+{
+    return pgm_read_byte(c) == '.' || pgm_read_byte(c) == ',' || pgm_read_byte(c) == ';' || pgm_read_byte(c) == '?' || pgm_read_byte(c) == '!';
+}
+
+const char* lcd_display_message_fullscreen_P(const char *msg)
 {
     // Disable update of the screen by the usual lcd_update() routine. 
     lcd_update_enable(false);
     lcd_implementation_clear();
     lcd.setCursor(0, 0);
+    const char *msgend = msg;
     for (int8_t row = 0; row < 4; ++ row) {
         while (pgm_is_whitespace(msg))
             ++ msg;
@@ -1384,8 +1390,8 @@ void lcd_display_message_fullscreen_P(const char *msg)
             break;
         lcd.setCursor(0, row);
         const char *msgend2 = msg + min(strlen_P(msg), 20);
-        const char *msgend = msgend2;
-        if (pgm_read_byte(msgend) != 0 && ! pgm_is_whitespace(msgend)) {
+        msgend = msgend2;
+        if (pgm_read_byte(msgend) != 0 && ! pgm_is_whitespace(msgend) && ! pgm_is_interpunction(msgend)) {
               // Splitting a word. Find the start of the current word.
             while (msgend > msg && ! pgm_is_whitespace(msgend - 1))
                  -- msgend;
@@ -1400,6 +1406,8 @@ void lcd_display_message_fullscreen_P(const char *msg)
             lcd.print(c);
         }
     }
+
+    return (pgm_read_byte(msgend) == 0) ? NULL : msgend;
 }
 
 void lcd_show_fullscreen_message_and_wait_P(const char *msg)

Firmware/ultralcd.h

@@ -40,7 +40,7 @@
   static void lcd_selftest_error(int _error_no, const char *_error_1, const char *_error_2);
   static void lcd_menu_statistics();
 
-  extern void lcd_display_message_fullscreen_P(const char *msg);
+  extern const char* lcd_display_message_fullscreen_P(const char *msg);
   extern void lcd_wait_for_click();
   extern void lcd_show_fullscreen_message_and_wait_P(const char *msg);
   // 0: no, 1: yes, -1: timeouted