New startup script setting. New dry run, check gcode switches. New system state variable. Lots of reorganizing.

(All v0.8 features installed. Still likely buggy, but now thourough
testing will need to start to squash them all. As soon as we're done,
this will be pushed to master and v0.9 development will be started.
Please report ANY issues to us so we can get this rolled out ASAP.)

- User startup script! A user can now save one (up to 5 as compile-time
option) block of g-code in EEPROM memory. This will be run everytime
Grbl resets. Mainly to be used as a way to set your preferences, like
G21, G54, etc.

- New dry run and check g-code switches. Dry run moves ALL motions at
rapids rate ignoring spindle, coolant, and dwell commands. For rapid
physical proofing of your code. The check g-code switch ignores all
motion and provides the user a way to check if there are any errors in
their program that Grbl may not like.

- Program restart! (sort of). Program restart is typically an advanced
feature that allows users to restart a program mid-stream. The check
g-code switch can perform this feature by enabling the switch at the
start of the program, and disabling it at the desired point with some
minimal changes.

- New system state variable. This state variable tracks all of the
different state processes that Grbl performs, i.e. cycle start, feed
hold, homing, etc. This is mainly for making managing of these task
easier and more clear.

- Position lost state variable. Only when homing is enabled, Grbl will
refuse to move until homing is completed and position is known. This is
mainly for safety. Otherwise, it will let users fend for themselves.

- Moved the default settings defines into config.h. The plan is to
eventually create a set of config.h's for particular as-built machines
to help users from doing it themselves.

- Moved around misc defines into .h files. And lots of other little
things.

nuts_bolts.h

@@ -66,36 +66,29 @@
 // #define                  bit(6) // bitmask 01000000
 // #define                  bit(7) // bitmask 10000000
 
-// Define bit flag masks for sys.switches. (8 flag limit)
-#define BITFLAG_BLOCK_DELETE  bit(0)
-#define BITFLAG_SINGLE_BLOCK  bit(1)
-#define BITFLAG_OPT_STOP      bit(2)
-// #define                    bit(3)
-// #define                    bit(4)
-// #define                    bit(5)
-// #define                    bit(6)
-// #define                    bit(7)
-
-// Define Grbl system states for sys.state
-
-// Define position lost in states?
-
+// Define system state bit map. The state variable primarily tracks the individual functions
+// of Grbl to manage each without overlapping. It is also used as a messaging flag for
+// critical events.
+#define STATE_IDLE   0 // Must be zero.
+#define STATE_QUEUED 1 // Indicates buffered blocks, awaiting cycle start.
+#define STATE_CYCLE  2 // Cycle is running
+#define STATE_HOLD   3 // Executing feed hold
+#define STATE_HOMING 4 // Performing homing cycle
+#define STATE_JOG    5 // Jogging mode is unique like homing.
+#define STATE_ALARM  6 // In alarm state. Locks out all but reset
+#define STATE_LOST   7 // Used to message position may be lost upon startup or event
+#define STATE_LIMIT  8 // Used to message hard limit triggered.
 
 // Define global system variables
 typedef struct {
   uint8_t abort;                 // System abort flag. Forces exit back to main loop for reset.
-  uint8_t feed_hold;             // Feed hold flag. Held true during feed hold. Released when ready to resume.
-  uint8_t auto_start;            // Planner auto-start flag. Toggled off during feed hold. Defaulted by settings.
-  uint8_t switches;              // Switches state bitflag variable. For features not governed by g-code.
-
-//   uint8_t state;                 // Tracks the current state of Grbl.
-// TODO: This may replace the functionality of the feed_hold and cycle_start variables. Need to 
-// make sure that overall processes don't change.
-
-  volatile uint8_t cycle_start;  // Cycle start flag. Set by stepper subsystem or main program. 
+  uint8_t state;                 // Tracks the current state of Grbl.
   volatile uint8_t execute;      // Global system runtime executor bitflag variable. See EXEC bitmasks.
   int32_t position[3];           // Real-time machine (aka home) position vector in steps. 
                                  // NOTE: This may need to be a volatile variable, if problems arise.   
+  uint8_t auto_start;            // Planner auto-start flag. Toggled off during feed hold. Defaulted by settings.
+//   uint8_t feed_hold;             // Feed hold flag. Held true during feed hold. Released when ready to resume.
+//   volatile uint8_t cycle_start;  // Cycle start flag. Set by stepper subsystem or main program. 
 } system_t;
 extern system_t sys;