v1.0 Beta Release.

- Tons of new stuff in this release, which is fairly stable and well
tested. However, much more is coming soon!

- Real-time parking motion with safety door. When this compile option
is enabled, an opened safety door will cause Grbl to automatically feed
hold, retract, de-energize the spindle/coolant, and parks near Z max.
After the door is closed and resume is commanded, this reverses and the
program continues as if nothing happened. This is also highly
configurable. See config.h for details.

- New spindle max and min rpm ‘$’ settings! This has been requested
often. Grbl will output 5V when commanded to turn on the spindle at its
max rpm, and 0.02V with min rpm. The voltage and the rpm range are
linear to each other. This should help users tweak their settings to
get close to true rpm’s.

- If the new max rpm ‘$’ setting is set = 0 or less than min rpm, the
spindle speed PWM pin will act like a regular on/off spindle enable
pin. On pin D11.

- BEWARE: Your old EEPROM settings will be wiped! The new spindle rpm
settings require a new settings version, so Grbl will automatically
wipe and restore the EEPROM with the new defaults.

- Control pin can now be inverted individually with a
CONTROL_INVERT_MASK in the cpu_map header file. Not typical for users
to need this, but handy to have.

- Fixed bug when Grbl receive too many characters in a line and
overflows. Previously it would respond with an error per overflow
character and another acknowledge upon an EOL character. This broke the
streaming protocol. Now fixed to only respond with an error after an
EOL character.

- Fixed a bug with the safety door during an ALARM mode. You now can’t
home or unlock the axes until the safety door has been closed. This is
for safety reasons (obviously.)

- Tweaked some the Mega2560 cpu_map settings . Increased segment buffer
size and fixed the spindle PWM settings to output at a higher PWM
frequency.

- Generalized the delay function used by G4 delay for use by parking
motion. Allows non-blocking status reports and real-time control during
re-energizing of the spindle and coolant.

- Added spindle rpm max and min defaults to default.h files.

- Added a new print float for rpm values.

grbl/config.h

@@ -102,6 +102,7 @@
 #define N_DECIMAL_RATEVALUE_INCH  1 // Rate or velocity value in in/min
 #define N_DECIMAL_RATEVALUE_MM    0 // Rate or velocity value in mm/min
 #define N_DECIMAL_SETTINGVALUE    3 // Decimals for floating point setting values
+#define N_DECIMAL_RPMVALUE        0 // RPM value in rotations per min.
 
 // If your machine has two limits switches wired in parallel to one axis, you will need to enable
 // this feature. Since the two switches are sharing a single pin, there is no way for Grbl to tell
@@ -138,9 +139,8 @@
 
 // After the safety door switch has been toggled and restored, this setting sets the power-up delay
 // between restoring the spindle and coolant and resuming the cycle.
-// NOTE: Delay value is defined in milliseconds from zero to 65,535. 
-#define SAFETY_DOOR_SPINDLE_DELAY 4000
-#define SAFETY_DOOR_COOLANT_DELAY 1000
+#define SAFETY_DOOR_SPINDLE_DELAY 4.0 // Float (seconds)
+#define SAFETY_DOOR_COOLANT_DELAY 1.0 // Float (seconds)
 
 // Enable CoreXY kinematics. Use ONLY with CoreXY machines. 
 // IMPORTANT: If homing is enabled, you must reconfigure the homing cycle #defines above to 
@@ -238,19 +238,14 @@
 // The hardware PWM output on pin D11 is required for variable spindle output voltages.
 #define VARIABLE_SPINDLE // Default enabled. Comment to disable.
 
-// Used by the variable spindle output only. These parameters set the maximum and minimum spindle speed
-// "S" g-code values to correspond to the maximum and minimum pin voltages. There are 256 discrete and 
-// equally divided voltage bins between the maximum and minimum spindle speeds. So for a 5V pin, 1000
-// max rpm, and 250 min rpm, the spindle output voltage would be set for the following "S" commands: 
-// "S1000" @ 5V, "S250" @ 0.02V, and "S625" @ 2.5V (mid-range). The pin outputs 0V when disabled.
-#define SPINDLE_MAX_RPM 1000.0 // Max spindle RPM. This value is equal to 100% duty cycle on the PWM.
-#define SPINDLE_MIN_RPM 0.0    // Min spindle RPM. This value is equal to (1/256) duty cycle on the PWM.
 
 // Used by variable spindle output only. This forces the PWM output to a minimum duty cycle when enabled.
-// When disabled, the PWM pin will still read 0V. Most users will not need this option, but it may be 
-// useful in certain scenarios. This setting does not update the minimum spindle RPM calculations. Any
-// spindle RPM output lower than this value will be set to this value.
-// #define MINIMUM_SPINDLE_PWM 5 // Default disabled. Uncomment to enable. Integer (0-255)
+// The PWM pin will still read 0V when the spindle is disabled. Most users will not need this option, but
+// it may be useful in certain scenarios. This minimum PWM settings coincides with the spindle rpm minimum
+// setting, like rpm max to max PWM. So the variable spindle pin will not output the voltage range between 
+// 0V for disabled and the voltage set by the minimum PWM for minimum rpm.
+// NOTE: Compute duty cycle at the minimum PWM by this equation: (% duty cycle)=(SPINDLE_MINIMUM_PWM/256)*100
+// #define SPINDLE_MINIMUM_PWM 5 // Default disabled. Uncomment to enable. Integer (0-255)
 
 // By default on a 328p(Uno), Grbl combines the variable spindle PWM and the enable into one pin to help 
 // preserve I/O pins. For certain setups, these may need to be separate pins. This configure option uses
@@ -383,6 +378,40 @@
 // NOTE: This option has no effect if SOFTWARE_DEBOUNCE is enabled.
 // #define HARD_LIMIT_FORCE_STATE_CHECK // Default disabled. Uncomment to enable.
 
+// Adjusts homing cycle search and locate scalars. These are the multipliers used by Grbl's
+// homing cycle to ensure the limit switches are engaged and cleared through each phase of 
+// the cycle. The search phase uses the axes max-travel setting times the SEARCH_SCALAR to
+// determine distance to look for the limit switch. Once found, the locate phase begins and
+// uses the homing pull-off distance setting times the LOCATE_SCALAR to pull-off and re-engage
+// the limit switch.
+// NOTE: Both of these values must be greater than 1.0 to ensure proper function.
+// #define HOMING_AXIS_SEARCH_SCALAR  1.5 // Uncomment to override defaults in limits.c.
+// #define HOMING_AXIS_LOCATE_SCALAR  10.0 // Uncomment to override defaults in limits.c.
+
+
+// Enables and configures parking motion methods upon a safety door state. Primarily for OEMs
+// that desire this feature for their integrated machines. At the moment, Grbl assumes that 
+// the parking motion only involves one axis, although the parking implementation was written
+// to be easily refactored for any number of motions on different axes by altering the parking 
+// source code. At this time, Grbl only supports parking one axis (typically the Z-axis) that 
+// moves in the positive direction upon retracting and negative direction upon restoring position.
+// The motion executes with a slow pull-out retraction motion, power-down, and a fast park. 
+// Restoring to the resume position follows these set motions in reverse: fast restore to 
+// pull-out position, power-up with a time-out, and plunge back to the original position at the
+// slower pull-out rate.
+// NOTE: Still a work-in-progress. Machine coordinates must be in all negative space and 
+// does not work with HOMING_FORCE_SET_ORIGIN enabled. Parking motion also moves only in 
+// positive direction.
+// #define PARKING_ENABLE  // Default disabled. Uncomment to enable
+
+// Configure options for the parking motion, if enabled.
+#define PARKING_AXIS Z_AXIS // Define which axis that performs the parking motion
+#define PARKING_TARGET -5.0 // Parking axis target. In mm, as machine coordinate [-max_travel,0].
+#define PARKING_RATE -1.0 // Parking fast rate after pull-out. In mm/min or (-1.0) for seek rate.
+#define PARKING_PULLOUT_RATE 250.0 // Pull-out/plunge slow feed rate in mm/min.
+#define PARKING_PULLOUT_INCREMENT 5.0 // Spindle pull-out and plunge distance in mm. Incremental distance.
+                                      // Must be positive value or equal to zero.
+
 
 // ---------------------------------------------------------------------------------------
 // COMPILE-TIME ERROR CHECKING OF DEFINE VALUES:
@@ -399,6 +428,12 @@
   #error "USE_SPINDLE_DIR_AS_ENABLE_PIN may only be used with a 328p processor"
 #endif
 
+#if defined(PARKING_ENABLE)
+  #if defined(HOMING_FORCE_SET_ORIGIN)
+    #error "HOMING_FORCE_SET_ORIGIN is not supported with PARKING_ENABLE at this time."
+  #endif
+#endif
+
 // ---------------------------------------------------------------------------------------