refactored block buffer into separate module motion_plan pending the addition of the actual look ahead planner

motion_plan.h

@@ -0,0 +1,57 @@
+/*
+  motion_plan.h - buffers movement commands and manages the acceleration profile plan
+  Part of Grbl
+
+  Copyright (c) 2009-2011 Simen Svale Skogsrud
+
+  Grbl is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  Grbl is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef motion_plan_h
+#define motion_plan_h
+                 
+#include <inttypes.h>
+
+// Pick a suitable block-buffer size
+#ifdef __AVR_ATmega328P__
+#define BLOCK_BUFFER_SIZE 20   // Atmega 328 has one full kilobyte of extra RAM!
+#else
+#define BLOCK_BUFFER_SIZE 5
+#endif
+
+// 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.
+struct Block {
+  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)
+  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
+  // Values used for acceleration management
+  double  speed_x, speed_y, speed_z;   // Nominal mm/minute for each axis
+  uint32_t initial_rate;              // The jerk-adjusted step rate at start of block
+  int16_t rate_delta;                 // The steps/minute to add or subtract when changing speed (must be positive)
+  uint16_t accelerate_ticks;          // The number of acceleration-ticks to accelerate 
+  uint16_t plateau_ticks;             // The number of acceleration-ticks to maintain top speed
+};
+      
+extern struct Block block_buffer[BLOCK_BUFFER_SIZE]; // A ring buffer for motion instructions
+extern volatile int block_buffer_head;           // Index of the next block to be pushed
+extern volatile int block_buffer_tail;           // Index of the block to process now
+
+// Calculates trapezoid parameters so that the entry- and exit-speed is compensated by the provided factors.
+// In practice both factors must be in the range 0 ... 1.0
+void calculate_trapezoid_for_block(struct Block *block, double entry_factor, double exit_factor);
+
+#endif