Initial v0.8 ALPHA commit. Features multi-tasking run-time command execution (feed hold, cycle start, reset, status query). Extensive re-structuring of code for future features.

- ALPHA status. - Multitasking ability with run-time command executions
for real-time control and feedback. - Decelerating feed hold and resume
during operation. - System abort/reset, which immediately kills all
movement and re-initializes grbl. - Re-structured grbl to easily allow
for new features: Status reporting, jogging, backlash compensation. (To
be completed in the following releases.) - Resized TX/RX serial buffers
(32/128 bytes) - Increased planner buffer size to 20 blocks. - Updated
documentation.

planner.h

@@ -27,12 +27,12 @@
 // This struct is used when buffering the setup for each linear movement "nominal" values are as specified in 
 // the source g-code and may never actually be reached if acceleration management is active.
 typedef struct {
+
   // Fields used by the bresenham algorithm for tracing the line
-  uint32_t steps_x, steps_y, steps_z; // Step count along each axis
   uint8_t  direction_bits;            // The direction bit set for this block (refers to *_DIRECTION_BIT in config.h)
+  uint32_t steps_x, steps_y, steps_z; // Step count along each axis
   int32_t  step_event_count;          // The number of step events required to complete this block
-  uint32_t nominal_rate;              // The nominal step rate for this block in step_events/minute
-  
+
   // Fields used by the motion planner to manage acceleration
   double nominal_speed;               // The nominal speed for this block in mm/min  
   double entry_speed;                 // Entry speed at previous-current junction in mm/min
@@ -42,12 +42,13 @@ typedef struct {
   uint8_t nominal_length_flag;        // Planner flag for nominal speed always reached
 
   // Settings for the trapezoid generator
-  uint32_t initial_rate;              // The jerk-adjusted step rate at start of block  
-  uint32_t final_rate;                // The minimal rate at exit
+  uint32_t initial_rate;              // The step rate at start of block  
+  uint32_t final_rate;                // The step rate at end of block
   int32_t rate_delta;                 // The steps/minute to add or subtract when changing speed (must be positive)
   uint32_t accelerate_until;          // The index of the step event on which to stop acceleration
   uint32_t decelerate_after;          // The index of the step event on which to start decelerating
-  
+  uint32_t nominal_rate;              // The nominal step rate for this block in step_events/minute
+
 } block_t;
       
 // Initialize the motion plan subsystem      
@@ -65,13 +66,19 @@ void plan_discard_current_block();
 // Gets the current block. Returns NULL if buffer empty
 block_t *plan_get_current_block();
 
-// Enables or disables acceleration-management for upcoming blocks
-void plan_set_acceleration_manager_enabled(uint8_t enabled);
-
-// Is acceleration-management currently enabled?
-int plan_is_acceleration_manager_enabled();
-
 // Reset the position vector
-void plan_set_current_position(double x, double y, double z); 
+void plan_set_current_position(double x, double y, double z);
+
+// Reinitialize plan with a partially completed block
+void plan_cycle_reinitialize(int32_t step_events_remaining);
+
+// Reset buffer
+void plan_reset_buffer();
+
+// Returns the status of the block ring buffer. True, if buffer is full.
+uint8_t plan_check_full_buffer();
+
+// Block until all buffered steps are executed
+void plan_synchronize();
 
 #endif