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/motion_control.c

@@ -67,10 +67,11 @@
   } while (1);
 
   // Plan and queue motion into planner buffer
+//   uint8_t plan_status; // Not used in normal operation.
   #ifdef USE_LINE_NUMBERS
-    plan_buffer_line(target, feed_rate, invert_feed_rate, line_number);
+    plan_buffer_line(target, feed_rate, invert_feed_rate, false, line_number);
   #else
-    plan_buffer_line(target, feed_rate, invert_feed_rate);
+    plan_buffer_line(target, feed_rate, invert_feed_rate, false);
   #endif
 }
 
@@ -202,17 +203,9 @@
 // Execute dwell in seconds.
 void mc_dwell(float seconds) 
 {
-   if (sys.state == STATE_CHECK_MODE) { return; }
-   
-   uint16_t i = floor(1000/DWELL_TIME_STEP*seconds);
-   protocol_buffer_synchronize();
-   delay_ms(floor(1000*seconds-i*DWELL_TIME_STEP)); // Delay millisecond remainder.
-   while (i-- > 0) {
-     // NOTE: Check and execute realtime commands during dwell every <= DWELL_TIME_STEP milliseconds.
-     protocol_execute_realtime();
-     if (sys.abort) { return; }
-     _delay_ms(DWELL_TIME_STEP); // Delay DWELL_TIME_STEP increment
-   }
+  if (sys.state == STATE_CHECK_MODE) { return; }
+  protocol_buffer_synchronize();
+  delay_sec(seconds, DELAY_MODE_DWELL);
 }
 
 
@@ -334,6 +327,32 @@ void mc_homing_cycle()
 }
 
 
+// Plans and executes the single special motion case for parking. Independent of main planner buffer.
+// NOTE: Uses the always free planner ring buffer head to store motion parameters for execution.
+void mc_parking_motion(float *parking_target, float feed_rate) 
+{
+  if (sys.abort) { return; } // Block during abort.
+  
+  uint8_t plan_status = plan_buffer_line(parking_target, feed_rate, false, true);
+  if (plan_status) {
+		bit_true(sys.step_control, STEP_CONTROL_EXECUTE_PARK); 
+		bit_false(sys.step_control, STEP_CONTROL_END_MOTION); // Allow parking motion to execute, if feed hold is active.
+    st_parking_setup_buffer(); // Setup step segment buffer for special parking motion case
+		st_prep_buffer();
+		st_wake_up();     
+		do {
+			protocol_exec_rt_system();
+			if (sys.abort) { return; }
+		} while (sys.step_control & STEP_CONTROL_EXECUTE_PARK);  
+		st_parking_restore_buffer(); // Restore step segment buffer to normal run state.
+	} else {
+    bit_false(sys.step_control, STEP_CONTROL_EXECUTE_PARK);
+		protocol_exec_rt_system();
+  }
+
+}
+
+
 // Method to ready the system to reset by setting the realtime reset command and killing any
 // active processes in the system. This also checks if a system reset is issued while Grbl
 // is in a motion state. If so, kills the steppers and sets the system alarm to flag position
@@ -353,7 +372,8 @@ void mc_reset()
     // NOTE: If steppers are kept enabled via the step idle delay setting, this also keeps
     // the steppers enabled by avoiding the go_idle call altogether, unless the motion state is
     // violated, by which, all bets are off.
-    if ((sys.state & (STATE_CYCLE | STATE_HOMING)) || (sys.suspend == SUSPEND_ENABLE_HOLD)) {
+    if ((sys.state & (STATE_CYCLE | STATE_HOMING)) || 
+    		(sys.step_control & (STEP_CONTROL_EXECUTE_HOLD | STEP_CONTROL_EXECUTE_PARK))) {
       if (sys.state == STATE_HOMING) { bit_true_atomic(sys.rt_exec_alarm, EXEC_ALARM_HOMING_FAIL); }
       else { bit_true_atomic(sys.rt_exec_alarm, EXEC_ALARM_ABORT_CYCLE); }
       st_go_idle(); // Force kill steppers. Position has likely been lost.