Revision:
0:8f0d870509fe
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/grbl/planner.c	Mon Sep 04 12:04:13 2017 +0000
@@ -0,0 +1,523 @@
+/*
+  planner.c - buffers movement commands and manages the acceleration profile plan
+  Part of Grbl
+
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
+  Copyright (c) 2009-2011 Simen Svale Skogsrud
+  Copyright (c) 2011 Jens Geisler
+
+  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/>.
+*/
+
+#include "grbl.h"
+
+
+static plan_block_t block_buffer[BLOCK_BUFFER_SIZE];  // A ring buffer for motion instructions
+static uint8_t block_buffer_tail;     // Index of the block to process now
+static uint8_t block_buffer_head;     // Index of the next block to be pushed
+static uint8_t next_buffer_head;      // Index of the next buffer head
+static uint8_t block_buffer_planned;  // Index of the optimally planned block
+
+// Define planner variables
+typedef struct {
+  int32_t position[N_AXIS];          // The planner position of the tool in absolute steps. Kept separate
+                                     // from g-code position for movements requiring multiple line motions,
+                                     // i.e. arcs, canned cycles, and backlash compensation.
+  float previous_unit_vec[N_AXIS];   // Unit vector of previous path line segment
+  float previous_nominal_speed;  // Nominal speed of previous path line segment
+} planner_t;
+static planner_t pl;
+
+
+// Returns the index of the next block in the ring buffer. Also called by stepper segment buffer.
+uint8_t plan_next_block_index(uint8_t block_index)
+{
+  block_index++;
+  if (block_index == BLOCK_BUFFER_SIZE) { block_index = 0; }
+  return(block_index);
+}
+
+
+// Returns the index of the previous block in the ring buffer
+static uint8_t plan_prev_block_index(uint8_t block_index)
+{
+  if (block_index == 0) { block_index = BLOCK_BUFFER_SIZE; }
+  block_index--;
+  return(block_index);
+}
+
+
+/*                            PLANNER SPEED DEFINITION
+                                     +--------+   <- current->nominal_speed
+                                    /          \
+         current->entry_speed ->   +            \
+                                   |             + <- next->entry_speed (aka exit speed)
+                                   +-------------+
+                                       time -->
+
+  Recalculates the motion plan according to the following basic guidelines:
+
+    1. Go over every feasible block sequentially in reverse order and calculate the junction speeds
+        (i.e. current->entry_speed) such that:
+      a. No junction speed exceeds the pre-computed maximum junction speed limit or nominal speeds of
+         neighboring blocks.
+      b. A block entry speed cannot exceed one reverse-computed from its exit speed (next->entry_speed)
+         with a maximum allowable deceleration over the block travel distance.
+      c. The last (or newest appended) block is planned from a complete stop (an exit speed of zero).
+    2. Go over every block in chronological (forward) order and dial down junction speed values if
+      a. The exit speed exceeds the one forward-computed from its entry speed with the maximum allowable
+         acceleration over the block travel distance.
+
+  When these stages are complete, the planner will have maximized the velocity profiles throughout the all
+  of the planner blocks, where every block is operating at its maximum allowable acceleration limits. In
+  other words, for all of the blocks in the planner, the plan is optimal and no further speed improvements
+  are possible. If a new block is added to the buffer, the plan is recomputed according to the said
+  guidelines for a new optimal plan.
+
+  To increase computational efficiency of these guidelines, a set of planner block pointers have been
+  created to indicate stop-compute points for when the planner guidelines cannot logically make any further
+  changes or improvements to the plan when in normal operation and new blocks are streamed and added to the
+  planner buffer. For example, if a subset of sequential blocks in the planner have been planned and are
+  bracketed by junction velocities at their maximums (or by the first planner block as well), no new block
+  added to the planner buffer will alter the velocity profiles within them. So we no longer have to compute
+  them. Or, if a set of sequential blocks from the first block in the planner (or a optimal stop-compute
+  point) are all accelerating, they are all optimal and can not be altered by a new block added to the
+  planner buffer, as this will only further increase the plan speed to chronological blocks until a maximum
+  junction velocity is reached. However, if the operational conditions of the plan changes from infrequently
+  used feed holds or feedrate overrides, the stop-compute pointers will be reset and the entire plan is
+  recomputed as stated in the general guidelines.
+
+  Planner buffer index mapping:
+  - block_buffer_tail: Points to the beginning of the planner buffer. First to be executed or being executed.
+  - block_buffer_head: Points to the buffer block after the last block in the buffer. Used to indicate whether
+      the buffer is full or empty. As described for standard ring buffers, this block is always empty.
+  - next_buffer_head: Points to next planner buffer block after the buffer head block. When equal to the
+      buffer tail, this indicates the buffer is full.
+  - block_buffer_planned: Points to the first buffer block after the last optimally planned block for normal
+      streaming operating conditions. Use for planning optimizations by avoiding recomputing parts of the
+      planner buffer that don't change with the addition of a new block, as describe above. In addition,
+      this block can never be less than block_buffer_tail and will always be pushed forward and maintain
+      this requirement when encountered by the plan_discard_current_block() routine during a cycle.
+
+  NOTE: Since the planner only computes on what's in the planner buffer, some motions with lots of short
+  line segments, like G2/3 arcs or complex curves, may seem to move slow. This is because there simply isn't
+  enough combined distance traveled in the entire buffer to accelerate up to the nominal speed and then
+  decelerate to a complete stop at the end of the buffer, as stated by the guidelines. If this happens and
+  becomes an annoyance, there are a few simple solutions: (1) Maximize the machine acceleration. The planner
+  will be able to compute higher velocity profiles within the same combined distance. (2) Maximize line
+  motion(s) distance per block to a desired tolerance. The more combined distance the planner has to use,
+  the faster it can go. (3) Maximize the planner buffer size. This also will increase the combined distance
+  for the planner to compute over. It also increases the number of computations the planner has to perform
+  to compute an optimal plan, so select carefully. The Arduino 328p memory is already maxed out, but future
+  ARM versions should have enough memory and speed for look-ahead blocks numbering up to a hundred or more.
+
+*/
+static void planner_recalculate()
+{
+  // Initialize block index to the last block in the planner buffer.
+  uint8_t block_index = plan_prev_block_index(block_buffer_head);
+
+  // Bail. Can't do anything with one only one plan-able block.
+  if (block_index == block_buffer_planned) { return; }
+
+  // Reverse Pass: Coarsely maximize all possible deceleration curves back-planning from the last
+  // block in buffer. Cease planning when the last optimal planned or tail pointer is reached.
+  // NOTE: Forward pass will later refine and correct the reverse pass to create an optimal plan.
+  float entry_speed_sqr;
+  plan_block_t *next;
+  plan_block_t *current = &block_buffer[block_index];
+
+  // Calculate maximum entry speed for last block in buffer, where the exit speed is always zero.
+  current->entry_speed_sqr = min( current->max_entry_speed_sqr, 2*current->acceleration*current->millimeters);
+
+  block_index = plan_prev_block_index(block_index);
+  if (block_index == block_buffer_planned) { // Only two plannable blocks in buffer. Reverse pass complete.
+    // Check if the first block is the tail. If so, notify stepper to update its current parameters.
+    if (block_index == block_buffer_tail) { st_update_plan_block_parameters(); }
+  } else { // Three or more plan-able blocks
+    while (block_index != block_buffer_planned) {
+      next = current;
+      current = &block_buffer[block_index];
+      block_index = plan_prev_block_index(block_index);
+
+      // Check if next block is the tail block(=planned block). If so, update current stepper parameters.
+      if (block_index == block_buffer_tail) { st_update_plan_block_parameters(); }
+
+      // Compute maximum entry speed decelerating over the current block from its exit speed.
+      if (current->entry_speed_sqr != current->max_entry_speed_sqr) {
+        entry_speed_sqr = next->entry_speed_sqr + 2*current->acceleration*current->millimeters;
+        if (entry_speed_sqr < current->max_entry_speed_sqr) {
+          current->entry_speed_sqr = entry_speed_sqr;
+        } else {
+          current->entry_speed_sqr = current->max_entry_speed_sqr;
+        }
+      }
+    }
+  }
+
+  // Forward Pass: Forward plan the acceleration curve from the planned pointer onward.
+  // Also scans for optimal plan breakpoints and appropriately updates the planned pointer.
+  next = &block_buffer[block_buffer_planned]; // Begin at buffer planned pointer
+  block_index = plan_next_block_index(block_buffer_planned);
+  while (block_index != block_buffer_head) {
+    current = next;
+    next = &block_buffer[block_index];
+
+    // Any acceleration detected in the forward pass automatically moves the optimal planned
+    // pointer forward, since everything before this is all optimal. In other words, nothing
+    // can improve the plan from the buffer tail to the planned pointer by logic.
+    if (current->entry_speed_sqr < next->entry_speed_sqr) {
+      entry_speed_sqr = current->entry_speed_sqr + 2*current->acceleration*current->millimeters;
+      // If true, current block is full-acceleration and we can move the planned pointer forward.
+      if (entry_speed_sqr < next->entry_speed_sqr) {
+        next->entry_speed_sqr = entry_speed_sqr; // Always <= max_entry_speed_sqr. Backward pass sets this.
+        block_buffer_planned = block_index; // Set optimal plan pointer.
+      }
+    }
+
+    // Any block set at its maximum entry speed also creates an optimal plan up to this
+    // point in the buffer. When the plan is bracketed by either the beginning of the
+    // buffer and a maximum entry speed or two maximum entry speeds, every block in between
+    // cannot logically be further improved. Hence, we don't have to recompute them anymore.
+    if (next->entry_speed_sqr == next->max_entry_speed_sqr) { block_buffer_planned = block_index; }
+    block_index = plan_next_block_index( block_index );
+  }
+}
+
+
+void plan_reset()
+{
+  memset(&pl, 0, sizeof(planner_t)); // Clear planner struct
+  plan_reset_buffer();
+}
+
+
+void plan_reset_buffer()
+{
+  block_buffer_tail = 0;
+  block_buffer_head = 0; // Empty = tail
+  next_buffer_head = 1; // plan_next_block_index(block_buffer_head)
+  block_buffer_planned = 0; // = block_buffer_tail;
+}
+
+
+void plan_discard_current_block()
+{
+  if (block_buffer_head != block_buffer_tail) { // Discard non-empty buffer.
+    uint8_t block_index = plan_next_block_index( block_buffer_tail );
+    // Push block_buffer_planned pointer, if encountered.
+    if (block_buffer_tail == block_buffer_planned) { block_buffer_planned = block_index; }
+    block_buffer_tail = block_index;
+  }
+}
+
+
+// Returns address of planner buffer block used by system motions. Called by segment generator.
+plan_block_t *plan_get_system_motion_block()
+{
+  return(&block_buffer[block_buffer_head]);
+}
+
+
+// Returns address of first planner block, if available. Called by various main program functions.
+plan_block_t *plan_get_current_block()
+{
+  if (block_buffer_head == block_buffer_tail) { return(NULL); } // Buffer empty
+  return(&block_buffer[block_buffer_tail]);
+}
+
+
+float plan_get_exec_block_exit_speed_sqr()
+{
+  uint8_t block_index = plan_next_block_index(block_buffer_tail);
+  if (block_index == block_buffer_head) { return( 0.0 ); }
+  return( block_buffer[block_index].entry_speed_sqr );
+}
+
+
+// Returns the availability status of the block ring buffer. True, if full.
+uint8_t plan_check_full_buffer()
+{
+  if (block_buffer_tail == next_buffer_head) { return(true); }
+  return(false);
+}
+
+
+// Computes and returns block nominal speed based on running condition and override values.
+// NOTE: All system motion commands, such as homing/parking, are not subject to overrides.
+float plan_compute_profile_nominal_speed(plan_block_t *block)
+{
+  float nominal_speed = block->programmed_rate;
+  if (block->condition & PL_COND_FLAG_RAPID_MOTION) { nominal_speed *= (0.01f*sys.r_override); }
+  else {
+    if (!(block->condition & PL_COND_FLAG_NO_FEED_OVERRIDE)) { nominal_speed *= (0.01f*sys.f_override); }
+    if (nominal_speed > block->rapid_rate) { nominal_speed = block->rapid_rate; }
+  }
+  if (nominal_speed > MINIMUM_FEED_RATE) { return(nominal_speed); }
+  return(MINIMUM_FEED_RATE);
+}
+
+
+// Computes and updates the max entry speed (sqr) of the block, based on the minimum of the junction's
+// previous and current nominal speeds and max junction speed.
+static void plan_compute_profile_parameters(plan_block_t *block, float nominal_speed, float prev_nominal_speed)
+{
+  // Compute the junction maximum entry based on the minimum of the junction speed and neighboring nominal speeds.
+  if (nominal_speed > prev_nominal_speed) { block->max_entry_speed_sqr = prev_nominal_speed*prev_nominal_speed; }
+  else { block->max_entry_speed_sqr = nominal_speed*nominal_speed; }
+  if (block->max_entry_speed_sqr > block->max_junction_speed_sqr) { block->max_entry_speed_sqr = block->max_junction_speed_sqr; }
+}
+
+
+// Re-calculates buffered motions profile parameters upon a motion-based override change.
+void plan_update_velocity_profile_parameters()
+{
+  uint8_t block_index = block_buffer_tail;
+  plan_block_t *block;
+  float nominal_speed;
+  float prev_nominal_speed = SOME_LARGE_VALUE; // Set high for first block nominal speed calculation.
+  while (block_index != block_buffer_head) {
+    block = &block_buffer[block_index];
+    nominal_speed = plan_compute_profile_nominal_speed(block);
+    plan_compute_profile_parameters(block, nominal_speed, prev_nominal_speed);
+    prev_nominal_speed = nominal_speed;
+    block_index = plan_next_block_index(block_index);
+  }
+  pl.previous_nominal_speed = prev_nominal_speed; // Update prev nominal speed for next incoming block.
+}
+
+
+/* Add a new linear movement to the buffer. target[N_AXIS] is the signed, absolute target position
+   in millimeters. Feed rate specifies the speed of the motion. If feed rate is inverted, the feed
+   rate is taken to mean "frequency" and would complete the operation in 1/feed_rate minutes.
+   All position data passed to the planner must be in terms of machine position to keep the planner
+   independent of any coordinate system changes and offsets, which are handled by the g-code parser.
+   NOTE: Assumes buffer is available. Buffer checks are handled at a higher level by motion_control.
+   In other words, the buffer head is never equal to the buffer tail.  Also the feed rate input value
+   is used in three ways: as a normal feed rate if invert_feed_rate is false, as inverse time if
+   invert_feed_rate is true, or as seek/rapids rate if the feed_rate value is negative (and
+   invert_feed_rate always false).
+   The system motion condition tells the planner to plan a motion in the always unused block buffer
+   head. It avoids changing the planner state and preserves the buffer to ensure subsequent gcode
+   motions are still planned correctly, while the stepper module only points to the block buffer head
+   to execute the special system motion. */
+uint8_t plan_buffer_line(float *target, plan_line_data_t *pl_data)
+{
+  // Prepare and initialize new block. Copy relevant pl_data for block execution.
+  plan_block_t *block = &block_buffer[block_buffer_head];
+  memset(block,0,sizeof(plan_block_t)); // Zero all block values.
+  block->condition = pl_data->condition;
+  #ifdef VARIABLE_SPINDLE
+    block->spindle_speed = pl_data->spindle_speed;
+  #endif
+  #ifdef USE_LINE_NUMBERS
+    block->line_number = pl_data->line_number;
+  #endif
+
+  // Compute and store initial move distance data.
+  int32_t target_steps[N_AXIS], position_steps[N_AXIS];
+  float unit_vec[N_AXIS], delta_mm;
+  uint8_t idx;
+
+  // Copy position data based on type of motion being planned.
+  if (block->condition & PL_COND_FLAG_SYSTEM_MOTION) {
+#ifdef COREXY
+    position_steps[X_AXIS] = system_convert_corexy_to_x_axis_steps(sys_position);
+    position_steps[Y_AXIS] = system_convert_corexy_to_y_axis_steps(sys_position);
+    position_steps[Z_AXIS] = sys_position[Z_AXIS];
+#else
+    memcpy(position_steps, sys_position, sizeof(sys_position));
+#endif
+  }
+  else { memcpy(position_steps, pl.position, sizeof(pl.position)); }
+
+  #ifdef COREXY
+    target_steps[A_MOTOR] = lround(target[A_MOTOR]*settings.steps_per_mm[A_MOTOR]);
+    target_steps[B_MOTOR] = lround(target[B_MOTOR]*settings.steps_per_mm[B_MOTOR]);
+    block->steps[A_MOTOR] = labs((target_steps[X_AXIS]-position_steps[X_AXIS]) + (target_steps[Y_AXIS]-position_steps[Y_AXIS]));
+    block->steps[B_MOTOR] = labs((target_steps[X_AXIS]-position_steps[X_AXIS]) - (target_steps[Y_AXIS]-position_steps[Y_AXIS]));
+  #endif
+
+  for (idx=0; idx<N_AXIS; idx++) {
+    // Calculate target position in absolute steps, number of steps for each axis, and determine max step events.
+    // Also, compute individual axes distance for move and prep unit vector calculations.
+    // NOTE: Computes true distance from converted step values.
+    #ifdef COREXY
+      if ( !(idx == A_MOTOR) && !(idx == B_MOTOR) ) {
+        target_steps[idx] = lroundf(target[idx]*settings.steps_per_mm[idx]);
+        block->steps[idx] = fabsf(target_steps[idx]-position_steps[idx]);
+      }
+      block->step_event_count = max(block->step_event_count, block->steps[idx]);
+      if (idx == A_MOTOR) {
+        delta_mm = (target_steps[X_AXIS]-position_steps[X_AXIS] + target_steps[Y_AXIS]-position_steps[Y_AXIS])/settings.steps_per_mm[idx];
+      } else if (idx == B_MOTOR) {
+        delta_mm = (target_steps[X_AXIS]-position_steps[X_AXIS] - target_steps[Y_AXIS]+position_steps[Y_AXIS])/settings.steps_per_mm[idx];
+      } else {
+        delta_mm = (target_steps[idx] - position_steps[idx])/settings.steps_per_mm[idx];
+      }
+    #else
+      target_steps[idx] = lroundf(target[idx]*settings.steps_per_mm[idx]);
+      block->steps[idx] = fabsf(target_steps[idx]-position_steps[idx]);
+      block->step_event_count = max(block->step_event_count, block->steps[idx]);
+      delta_mm = (target_steps[idx] - position_steps[idx])/settings.steps_per_mm[idx];
+	  #endif
+    unit_vec[idx] = delta_mm; // Store unit vector numerator
+
+    // Set direction bits. Bit enabled always means direction is negative.
+    if (delta_mm < 0.0f ) { block->direction_bits |= direction_pin_mask[idx]; }
+  }
+
+  // Bail if this is a zero-length block. Highly unlikely to occur.
+  if (block->step_event_count == 0) { return(PLAN_EMPTY_BLOCK); }
+
+  // Calculate the unit vector of the line move and the block maximum feed rate and acceleration scaled
+  // down such that no individual axes maximum values are exceeded with respect to the line direction.
+  // NOTE: This calculation assumes all axes are orthogonal (Cartesian) and works with ABC-axes,
+  // if they are also orthogonal/independent. Operates on the absolute value of the unit vector.
+  block->millimeters = convert_delta_vector_to_unit_vector(unit_vec);
+  block->acceleration = limit_value_by_axis_maximum(settings.acceleration, unit_vec);
+  block->rapid_rate = limit_value_by_axis_maximum(settings.max_rate, unit_vec);
+
+  // Store programmed rate.
+  if (block->condition & PL_COND_FLAG_RAPID_MOTION) { block->programmed_rate = block->rapid_rate; }
+  else { 
+    block->programmed_rate = pl_data->feed_rate;
+    if (block->condition & PL_COND_FLAG_INVERSE_TIME) { block->programmed_rate *= block->millimeters; }
+  }
+
+  // TODO: Need to check this method handling zero junction speeds when starting from rest.
+  if ((block_buffer_head == block_buffer_tail) || (block->condition & PL_COND_FLAG_SYSTEM_MOTION)) {
+
+    // Initialize block entry speed as zero. Assume it will be starting from rest. Planner will correct this later.
+    // If system motion, the system motion block always is assumed to start from rest and end at a complete stop.
+    block->entry_speed_sqr = 0.0f;
+    block->max_junction_speed_sqr = 0.0f; // Starting from rest. Enforce start from zero velocity.
+
+  } else {
+    // Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
+    // Let a circle be tangent to both previous and current path line segments, where the junction
+    // deviation is defined as the distance from the junction to the closest edge of the circle,
+    // colinear with the circle center. The circular segment joining the two paths represents the
+    // path of centripetal acceleration. Solve for max velocity based on max acceleration about the
+    // radius of the circle, defined indirectly by junction deviation. This may be also viewed as
+    // path width or max_jerk in the previous Grbl version. This approach does not actually deviate
+    // from path, but used as a robust way to compute cornering speeds, as it takes into account the
+    // nonlinearities of both the junction angle and junction velocity.
+    //
+    // NOTE: If the junction deviation value is finite, Grbl executes the motions in an exact path
+    // mode (G61). If the junction deviation value is zero, Grbl will execute the motion in an exact
+    // stop mode (G61.1) manner. In the future, if continuous mode (G64) is desired, the math here
+    // is exactly the same. Instead of motioning all the way to junction point, the machine will
+    // just follow the arc circle defined here. The Arduino doesn't have the CPU cycles to perform
+    // a continuous mode path, but ARM-based microcontrollers most certainly do.
+    //
+    // NOTE: The max junction speed is a fixed value, since machine acceleration limits cannot be
+    // changed dynamically during operation nor can the line move geometry. This must be kept in
+    // memory in the event of a feedrate override changing the nominal speeds of blocks, which can
+    // change the overall maximum entry speed conditions of all blocks.
+
+    float junction_unit_vec[N_AXIS];
+    float junction_cos_theta = 0.0f;
+    for (idx=0; idx<N_AXIS; idx++) {
+      junction_cos_theta -= pl.previous_unit_vec[idx]*unit_vec[idx];
+      junction_unit_vec[idx] = unit_vec[idx]-pl.previous_unit_vec[idx];
+    }
+
+    // NOTE: Computed without any expensive trig, sin() or acos(), by trig half angle identity of cos(theta).
+    if (junction_cos_theta > 0.999999f) {
+      //  For a 0 degree acute junction, just set minimum junction speed.
+      block->max_junction_speed_sqr = MINIMUM_JUNCTION_SPEED*MINIMUM_JUNCTION_SPEED;
+    } else {
+      if (junction_cos_theta < -0.999999f) {
+        // Junction is a straight line or 180 degrees. Junction speed is infinite.
+        block->max_junction_speed_sqr = SOME_LARGE_VALUE;
+      } else {
+        convert_delta_vector_to_unit_vector(junction_unit_vec);
+        float junction_acceleration = limit_value_by_axis_maximum(settings.acceleration, junction_unit_vec);
+        float sin_theta_d2 = sqrtf(0.5f*(1.0f-junction_cos_theta)); // Trig half angle identity. Always positive.
+        block->max_junction_speed_sqr = max( MINIMUM_JUNCTION_SPEED*MINIMUM_JUNCTION_SPEED,
+                       (junction_acceleration * settings.junction_deviation * sin_theta_d2)/(1.0f-sin_theta_d2) );
+      }
+    }
+  }
+
+  // Block system motion from updating this data to ensure next g-code motion is computed correctly.
+  if (!(block->condition & PL_COND_FLAG_SYSTEM_MOTION)) {
+    float nominal_speed = plan_compute_profile_nominal_speed(block);
+    plan_compute_profile_parameters(block, nominal_speed, pl.previous_nominal_speed);
+    pl.previous_nominal_speed = nominal_speed;
+
+    // Update previous path unit_vector and planner position.
+    memcpy(pl.previous_unit_vec, unit_vec, sizeof(unit_vec)); // pl.previous_unit_vec[] = unit_vec[]
+    memcpy(pl.position, target_steps, sizeof(target_steps)); // pl.position[] = target_steps[]
+
+    // New block is all set. Update buffer head and next buffer head indices.
+    block_buffer_head = next_buffer_head;
+    next_buffer_head = plan_next_block_index(block_buffer_head);
+
+    // Finish up by recalculating the plan with the new block.
+    planner_recalculate();
+  }
+  return(PLAN_OK);
+}
+
+
+// Reset the planner position vectors. Called by the system abort/initialization routine.
+void plan_sync_position()
+{
+  // TODO: For motor configurations not in the same coordinate frame as the machine position,
+  // this function needs to be updated to accomodate the difference.
+  uint8_t idx;
+  for (idx=0; idx<N_AXIS; idx++) {
+    #ifdef COREXY
+      if (idx==X_AXIS) {
+        pl.position[X_AXIS] = system_convert_corexy_to_x_axis_steps(sys_position);
+      } else if (idx==Y_AXIS) {
+        pl.position[Y_AXIS] = system_convert_corexy_to_y_axis_steps(sys_position);
+      } else {
+        pl.position[idx] = sys_position[idx];
+      }
+    #else
+      pl.position[idx] = sys_position[idx];
+    #endif
+  }
+}
+
+
+// Returns the number of available blocks are in the planner buffer.
+uint8_t plan_get_block_buffer_available()
+{
+  if (block_buffer_head >= block_buffer_tail) { return((BLOCK_BUFFER_SIZE-1)-(block_buffer_head-block_buffer_tail)); }
+  return((block_buffer_tail-block_buffer_head-1));
+}
+
+
+// Returns the number of active blocks are in the planner buffer.
+// NOTE: Deprecated. Not used unless classic status reports are enabled in config.h
+uint8_t plan_get_block_buffer_count()
+{
+  if (block_buffer_head >= block_buffer_tail) { return(block_buffer_head-block_buffer_tail); }
+  return(BLOCK_BUFFER_SIZE - (block_buffer_tail-block_buffer_head));
+}
+
+
+// Re-initialize buffer plan with a partially completed block, assumed to exist at the buffer tail.
+// Called after a steppers have come to a complete stop for a feed hold and the cycle is stopped.
+void plan_cycle_reinitialize()
+{
+  // Re-plan from a complete stop. Reset planner entry speeds and buffer planned pointer.
+  st_update_plan_block_parameters();
+  block_buffer_planned = block_buffer_tail;
+  planner_recalculate();
+}