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/system.h

@@ -59,12 +59,23 @@
 #define STATE_SAFETY_DOOR   bit(5) // Safety door is ajar. Feed holds and de-energizes system.
 #define STATE_MOTION_CANCEL bit(6) // Motion cancel by feed hold and return to idle. 
 
-// Define system suspend states.
-#define SUSPEND_DISABLE       0      // Must be zero.
-#define SUSPEND_ENABLE_HOLD   bit(0) // Enabled. Indicates the cycle is active and currently undergoing a hold.
-#define SUSPEND_ENABLE_READY  bit(1) // Ready to resume with a cycle start command.
-#define SUSPEND_ENERGIZE      bit(2) // Re-energizes output before resume.
-#define SUSPEND_MOTION_CANCEL bit(3) // Cancels resume motion. Used by probing routine.
+// Define system suspend flags. Used in various ways to manage suspend states and procedures.
+#define SUSPEND_DISABLE           0      // Must be zero.
+#define SUSPEND_HOLD_COMPLETE     bit(0) // Indicates initial feed hold is complete.
+#define SUSPEND_RESTART_RETRACT   bit(1) // Flag to indicate a retract from a restore parking motion.
+#define SUSPEND_RETRACT_COMPLETE  bit(2) // (Safety door only) Indicates retraction and de-energizing is complete.
+#define SUSPEND_INITIATE_RESTORE  bit(3) // (Safety door only) Flag to initiate resume procedures from a cycle start.
+#define SUSPEND_RESTORE_COMPLETE  bit(4) // (Safety door only) Indicates ready to resume normal operation.
+#define SUSPEND_SAFETY_DOOR_AJAR  bit(5) // Indicates suspend was initiated by a safety door state.
+#define SUSPEND_MOTION_CANCEL     bit(6) // Indicates a canceled resume motion. Currently used by probing routine.
+
+
+#define STEP_CONTROL_NORMAL_OP              0
+// #define STEP_CONTROL_RECOMPUTE_ACTIVE_BLOCK bit(0)
+#define STEP_CONTROL_END_MOTION             bit(1)
+#define STEP_CONTROL_EXECUTE_HOLD           bit(2)
+#define STEP_CONTROL_EXECUTE_PARK           bit(3)
+
 
 
 // Define global system variables
@@ -72,6 +83,7 @@ typedef struct {
   uint8_t abort;                 // System abort flag. Forces exit back to main loop for reset.
   uint8_t state;                 // Tracks the current state of Grbl.
   uint8_t suspend;               // System suspend bitflag variable that manages holds, cancels, and safety door.
+  uint8_t step_control;
 
   volatile uint8_t rt_exec_state;  // Global realtime executor bitflag variable for state management. See EXEC bitmasks.
   volatile uint8_t rt_exec_alarm;  // Global realtime executor bitflag variable for setting various alarms.