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Pushed limits active high option. Updated defaults.h. Misc bug fixes. Cleaned up codebase.

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- Pushed limit switch active high option (i.e. NC switches).

- Updated defaults.h to be in-line with the new settings.

- Refactored feed hold handling and step segment buffer to be more
generalized in effort to make adding feedrate overrides easier in the
future. Also made it a little more clean.

- Fixed G18 plane select issue. Now ZX-plane, rather than XZ-plane, per
right hand rule.

- Cleaned some of the system settings by more accurately renaming some
of the variables and removing old obsolete ones.

- Declared serial.c rx_buffer_tail to be volatile. No effect, since
avr-gcc automatically does this during compilation. Helps with porting
when using other compilers.

- Updated version number to v0.9b.

- Updates to README.md
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Sonny Jeon 2013-12-07 08:40:25 -07:00
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commit a87f25773c
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10
README.md
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@ -5,22 +5,24 @@ This branch serves only as a developmental platform for working on new ideas tha
------------
Grbl is a no-compromise, high performance, low cost alternative to parallel-port-based motion control for CNC milling. It will run on a vanilla Arduino (Duemillanove/Uno) as long as it sports an Atmega 328.
Grbl is a no-compromise, high performance, low cost alternative to parallel-port-based motion control for CNC milling. It will run on a vanilla Arduino (Duemillanove/Uno) as long as it sports an Atmega 328. (Other AVR CPUs are unofficially supported as well.)
The controller is written in highly optimized C utilizing every clever feature of the AVR-chips to achieve precise timing and asynchronous operation. It is able to m aintain more than 30kHz of stable, jitter free control pulses.
The controller is written in highly optimized C utilizing every clever feature of the AVR-chips to achieve precise timing and asynchronous operation. It is able to maintain up to 30kHz of stable, jitter free control pulses.
It accepts standards-compliant G-code and has been tested with the output of several CAM tools with no problems. Arcs, circles and helical motion are fully supported, as well as, other basic functional g-code commands. Functions and variables are not currently supported, but may be included in future releases in a form of a pre-processor.
It accepts standards-compliant G-code and has been tested with the output of several CAM tools with no problems. Arcs, circles and helical motion are fully supported, as well as, other basic functional g-code commands. Although canned cycles, functions, and variables are not currently supported (may in the future), GUIs can be built or modified easily to translate to straight g-code for Grbl.
Grbl includes full acceleration management with look ahead. That means the controller will look up to 18 motions into the future and plan its velocities ahead to deliver smooth acceleration and jerk-free cornering.
##Changelog for v0.9 from v0.8
- **ALPHA status: Under heavy development.**
- New stepper algorithm: Based on an inverse time algorithm, but modified to ensure steps are executed exactly. This algorithm performs a constant timer tick and has a hard limit of 30kHz maximum step frequency. It is also highly tuneable and should be very easy to port to other microcontroller architectures. Overall, a much better, smoother stepper algorithm with the capability of very high speeds.
- Planner optimizations: Multiple changes to increase planner execution speed and removed redundant variables.
- Planner optimizations: Planning computations improved four-fold or more. Changes include streaming optimizations by ignoring already optimized blocks and removing redundant variables and computations and offloading them to the stepper algorithm on an ad-hoc basis.
- Planner stability: Previous Grbl planners have all had a corruption issue in rare circumstances that becomes particularly problematic at high step frequencies and when jogging. The new planner is robust and incorruptible, meaning that we can fearlessly drive Grbl to it's highest limits. Combined with the new stepper algorithm and planner optimizations, this means 5x to 10x performance increases in our testing! This is all achieved through the introduction of an intermediary step segment buffer that "checks-out" steps from the planner buffer in real-time.
- Acceleration independence: Each axes may be defined with different acceleration parameters and Grbl will automagically calculate the maximum acceleration through a path depending on the direction traveled. This is very useful for machine that have very different axes properties, like the ShapeOko z-axis.
- Maximum velocity independence: As with acceleration, the maximum velocity of individual axes may be defined. All seek/rapids motions will move at these maximum rates, but never exceed any one axes. So, when two or more axes move, the limiting axis will move at its maximum rate, while the other axes are scaled down.
- Significantly improved arc performance: Arcs are now defined in terms of chordal tolerance, rather than segment length. Chordal tolerance will automatically scale all arc line segments depending on arc radius, such that the error does not exceed the tolerance value (default: 0.005 mm.) So, for larger radii arcs, Grbl can move faster through them, because the segments are always longer and the planner has more distance to plan with.
- Soft limits: Checks if any motion command exceeds workspace limits. Alarms out when found. Another safety feature, but, unlike hard limits, position does not get lost, as it forces a feed hold before erroring out.
- Pin mapping: In an effort for Grbl to be compatible with other AVR architectures, such as the 1280 or 2560, a new pin_map.h configuration file has been created to allow Grbl to be compiled for them. This is currently user supported, so your mileage may vary. If you run across a bug, please let us know or better send us a fix! Thanks in advance!
- New Grbl SIMULATOR by @jgeisler: A completely independent wrapper of the Grbl main source code that may be compiled as an executable on a computer. No Arduino required. Simply simulates the responses of Grbl as if it was on an Arduino. May be used for many things: checking out how Grbl works, pre-process moves for GUI graphics, debugging of new features, etc. Much left to do, but potentially very powerful, as the dummy AVR variables can be written to output anything you need.
- Homing routine updated: Sets workspace volume in all negative space regardless of limit switch position. Common on pro CNCs. Also reduces soft limits CPU overhead.
- Feedrate overrides: In the works, but planner has begun to be re-factored for this feature.

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/*
planner.c - buffers movement commands and manages the acceleration profile plan
Part of Grbl
Copyright (c) 2011-2013 Sungeun K. Jeon
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/>.
*/
/* The ring buffer implementation gleaned from the wiring_serial library by David A. Mellis. */
#include <inttypes.h>
#include <stdlib.h>
#include "planner.h"
#include "nuts_bolts.h"
#include "stepper.h"
#include "settings.h"
#include "config.h"
#include "protocol.h"
#define SOME_LARGE_VALUE 1.0E+38 // Used by rapids and acceleration maximization calculations. Just needs
// to be larger than any feasible (mm/min)^2 or mm/sec^2 value.
static plan_block_t block_buffer[BLOCK_BUFFER_SIZE]; // A ring buffer for motion instructions
static volatile 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_sqr; // 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.
// NOTE: Removed modulo (%) operator, which uses an expensive divide and multiplication.
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);
}
// Update the entry speed and millimeters remaining to execute for a partially completed block. Called only
// when the planner knows it will be changing the conditions of this block.
// TODO: Set up to be called from planner calculations. Need supporting code framework still, i.e. checking
// and executing this only when necessary, combine with the block_buffer_safe pointer.
// TODO: This is very similar to the planner reinitialize after a feed hold. Could make this do double duty.
void plan_update_partial_block(uint8_t block_index, float exit_speed_sqr)
{
// TODO: Need to make a condition to check if we need make these calculations. We don't if nothing has
// been executed or placed into segment buffer. This happens with the first block upon startup or if
// the segment buffer is exactly in between two blocks. Just check if the step_events_remaining is equal
// the total step_event_count in the block. If so, we don't have to do anything.
// !!! block index is the same as block_buffer_safe.
// See if we can reduce this down to just requesting the millimeters remaining..
uint8_t is_decelerating;
float millimeters_remaining = 0.0;
st_fetch_partial_block_parameters(block_index, &millimeters_remaining, &is_decelerating);
if (millimeters_remaining != 0.0) {
// Point to current block partially executed by stepper algorithm
plan_block_t *partial_block = plan_get_block_by_index(block_index);
// Compute the midway speed of the partially completely block at the end of the segment buffer.
if (is_decelerating) { // Block is decelerating
partial_block->entry_speed_sqr = exit_speed_sqr - 2*partial_block->acceleration*millimeters_remaining;
} else { // Block is accelerating or cruising
partial_block->entry_speed_sqr += 2*partial_block->acceleration*(partial_block->millimeters-millimeters_remaining);
partial_block->entry_speed_sqr = min(partial_block->entry_speed_sqr, partial_block->nominal_speed_sqr);
}
// Update only the relevant planner block information so the planner can plan correctly.
partial_block->millimeters = millimeters_remaining;
partial_block->max_entry_speed_sqr = partial_block->entry_speed_sqr; // Not sure if this needs to be updated.
}
}
/* 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_safe: Points to the first sequential planner block for which it is safe to recompute, which
is defined to be where the stepper's step segment buffer ends. This may or may not be the buffer tail,
since the step segment buffer queues steps which may have not finished executing and could span a few
blocks, if the block moves are very short.
- 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.
NOTE: All planner computations are performed in floating point to minimize numerical round-off errors.
When a planner block is executed, the floating point values are converted to fast integers by the stepper
algorithm segment buffer. See the stepper module for details.
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
segment(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);
// Query stepper module for safe planner block index to recalculate to, which corresponds to the end
// of the step segment buffer.
uint8_t block_buffer_safe = st_get_prep_block_index();
// TODO: Make sure that we don't have to check for the block_buffer_tail condition, if the stepper module
// returns a NULL pointer or something. This could happen when the segment buffer is empty. Although,
// this call won't return a NULL, only an index.. I have to make sure that this index is synced with the
// planner at all times.
// Recompute plan only when there is more than one planner block in the buffer. Can't do anything with one.
// NOTE: block_buffer_safe can be the last planner block if the segment buffer has completely queued up the
// remainder of the planner buffer. In this case, a new planner block will be treated as a single block.
if (block_index == block_buffer_safe) { // Also catches (head-1) = tail
// Just set block_buffer_planned pointer.
block_buffer_planned = block_index;
// TODO: Feedrate override of one block needs to update the partial block with an exit speed of zero. For
// a single added block and recalculate after a feed hold, we don't need to compute this, since we already
// know that the velocity starts and ends at zero. With an override, we can be traveling at some midblock
// rate, and we have to calculate the new velocity profile from it.
// plan_update_partial_block(block_index,0.0);
} else {
// TODO: If the nominal speeds change during a feedrate override, we need to recompute the max entry speeds for
// all junctions before proceeding.
// Initialize planner buffer pointers and indexing.
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);
// Reverse Pass: Coarsely maximize all possible deceleration curves back-planning from the last
// block in buffer. Cease planning when: (1) the last optimal planned pointer is reached.
// (2) the safe block pointer is reached, whereby the planned pointer is updated.
// NOTE: Forward pass will later refine and correct the reverse pass to create an optimal plan.
// NOTE: If the safe block is encountered before the planned block pointer, we know the safe block
// will be recomputed within the plan. So, we need to update it if it is partially completed.
float entry_speed_sqr;
plan_block_t *next;
block_index = plan_prev_block_index(block_index);
if (block_index == block_buffer_safe) { // !! OR plan pointer? Yes I think so.
// Only two plannable blocks in buffer. Compute previous block based on
// !!! May only work if a new block is being added. Not for an override. The exit speed isn't zero.
// !!! Need to make the current entry speed calculation after this.
plan_update_partial_block(block_index, 0.0);
block_buffer_planned = block_index;
} else {
// Three or more plan-able
while (block_index != block_buffer_planned) {
next = current;
current = &block_buffer[block_index];
// Increment block index early to check if the safe block is before the current block. If encountered,
// this is an exit condition as we can't go further than this block in the reverse pass.
block_index = plan_prev_block_index(block_index);
if (block_index == block_buffer_safe) {
// Check if the safe block is partially completed. If so, update it before its exit speed
// (=current->entry speed) is over-written.
// TODO: The update breaks with feedrate overrides, because the replanning process no longer has
// the previous nominal speed to update this block with. There will need to be something along the
// lines of a nominal speed change check and send the correct value to this function.
plan_update_partial_block(block_index,current->entry_speed_sqr);
// Set planned pointer at safe block and for loop exit after following computation is done.
block_buffer_planned = block_index;
}
// 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.
// TODO: Need to check if the planned flag logic is correct for all scenarios. It may not
// be for certain conditions. However, if the block reaches nominal speed, it can be a valid
// breakpoint substitute.
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; // Set optimal plan pointer
}
block_index = plan_next_block_index( block_index );
}
}
}
void plan_reset_buffer()
{
block_buffer_planned = block_buffer_tail;
}
void plan_init()
{
block_buffer_tail = 0;
block_buffer_head = 0; // Empty = tail
next_buffer_head = 1; // plan_next_block_index(block_buffer_head)
plan_reset_buffer();
memset(&pl, 0, sizeof(pl)); // Clear planner struct
}
void plan_discard_current_block()
{
if (block_buffer_head != block_buffer_tail) { // Discard non-empty buffer.
block_buffer_tail = plan_next_block_index( block_buffer_tail );
}
}
plan_block_t *plan_get_current_block()
{
if (block_buffer_head == block_buffer_tail) { // Buffer empty
plan_reset_buffer();
return(NULL);
}
return(&block_buffer[block_buffer_tail]);
}
plan_block_t *plan_get_block_by_index(uint8_t block_index)
{
if (block_buffer_head == block_index) { return(NULL); }
return(&block_buffer[block_index]);
}
// 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);
}
// Block until all buffered steps are executed or in a cycle state. Works with feed hold
// during a synchronize call, if it should happen. Also, waits for clean cycle end.
void plan_synchronize()
{
while (plan_get_current_block() || sys.state == STATE_CYCLE) {
protocol_execute_runtime(); // Check and execute run-time commands
if (sys.abort) { return; } // Check for system abort
}
}
/* 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). */
void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate)
{
// Prepare and initialize new block
plan_block_t *block = &block_buffer[block_buffer_head];
block->step_event_count = 0;
block->millimeters = 0;
block->direction_bits = 0;
block->acceleration = SOME_LARGE_VALUE; // Scaled down to maximum acceleration later
// Compute and store initial move distance data.
// TODO: After this for-loop, we don't touch the stepper algorithm data. Might be a good idea
// to try to keep these types of things completely separate from the planner for portability.
int32_t target_steps[N_AXIS];
float unit_vec[N_AXIS], delta_mm;
uint8_t idx;
for (idx=0; idx<N_AXIS; idx++) {
// Calculate target position in absolute steps. This conversion should be consistent throughout.
target_steps[idx] = lround(target[idx]*settings.steps_per_mm[idx]);
// Number of steps for each axis and determine max step events
block->steps[idx] = labs(target_steps[idx]-pl.position[idx]);
block->step_event_count = max(block->step_event_count, block->steps[idx]);
// Compute individual axes distance for move and prep unit vector calculations.
// NOTE: Computes true distance from converted step values.
delta_mm = (target_steps[idx] - pl.position[idx])/settings.steps_per_mm[idx];
unit_vec[idx] = delta_mm; // Store unit vector numerator. Denominator computed later.
// Set direction bits. Bit enabled always means direction is negative.
if (delta_mm < 0 ) { block->direction_bits |= get_direction_mask(idx); }
// Incrementally compute total move distance by Euclidean norm. First add square of each term.
block->millimeters += delta_mm*delta_mm;
}
block->millimeters = sqrt(block->millimeters); // Complete millimeters calculation with sqrt()
// Bail if this is a zero-length block. Highly unlikely to occur.
if (block->step_event_count == 0) { return; }
// Adjust feed_rate value to mm/min depending on type of rate input (normal, inverse time, or rapids)
// TODO: Need to distinguish a rapids vs feed move for overrides. Some flag of some sort.
if (feed_rate < 0) { feed_rate = SOME_LARGE_VALUE; } // Scaled down to absolute max/rapids rate later
else if (invert_feed_rate) { feed_rate = block->millimeters/feed_rate; }
// 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.
float inverse_unit_vec_value;
float inverse_millimeters = 1.0/block->millimeters; // Inverse millimeters to remove multiple float divides
float junction_cos_theta = 0;
for (idx=0; idx<N_AXIS; idx++) {
if (unit_vec[idx] != 0) { // Avoid divide by zero.
unit_vec[idx] *= inverse_millimeters; // Complete unit vector calculation
inverse_unit_vec_value = abs(1.0/unit_vec[idx]); // Inverse to remove multiple float divides.
// Check and limit feed rate against max individual axis velocities and accelerations
feed_rate = min(feed_rate,settings.max_velocity[idx]*inverse_unit_vec_value);
block->acceleration = min(block->acceleration,settings.acceleration[idx]*inverse_unit_vec_value);
// Incrementally compute cosine of angle between previous and current path. Cos(theta) of the junction
// between the current move and the previous move is simply the dot product of the two unit vectors,
// where prev_unit_vec is negative. Used later to compute maximum junction speed.
junction_cos_theta -= pl.previous_unit_vec[idx] * unit_vec[idx];
}
}
// TODO: Need to check this method handling zero junction speeds when starting from rest.
if (block_buffer_head == block_buffer_tail) {
// Initialize block entry speed as zero. Assume it will be starting from rest. Planner will correct this later.
block->entry_speed_sqr = 0.0;
block->max_junction_speed_sqr = 0.0; // 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.
*/
// NOTE: Computed without any expensive trig, sin() or acos(), by trig half angle identity of cos(theta).
float sin_theta_d2 = sqrt(0.5*(1.0-junction_cos_theta)); // Trig half angle identity. Always positive.
// TODO: Acceleration used in calculation needs to be limited by the minimum of the two junctions.
block->max_junction_speed_sqr = max( MINIMUM_JUNCTION_SPEED*MINIMUM_JUNCTION_SPEED,
(block->acceleration * settings.junction_deviation * sin_theta_d2)/(1.0-sin_theta_d2) );
}
// Store block nominal speed
block->nominal_speed_sqr = feed_rate*feed_rate; // (mm/min). Always > 0
// Compute the junction maximum entry based on the minimum of the junction speed and neighboring nominal speeds.
block->max_entry_speed_sqr = min(block->max_junction_speed_sqr,
min(block->nominal_speed_sqr,pl.previous_nominal_speed_sqr));
// Update previous path unit_vector and nominal speed (squared)
memcpy(pl.previous_unit_vec, unit_vec, sizeof(unit_vec)); // pl.previous_unit_vec[] = unit_vec[]
pl.previous_nominal_speed_sqr = block->nominal_speed_sqr;
// Update planner position
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();
// int32_t blength = block_buffer_head - block_buffer_tail;
// if (blength < 0) { blength += BLOCK_BUFFER_SIZE; }
// printInteger(blength);
}
// Reset the planner position vectors. Called by the system abort/initialization routine.
void plan_sync_position()
{
uint8_t idx;
for (idx=0; idx<N_AXIS; idx++) {
pl.position[idx] = sys.position[idx];
}
}
/* STEPPER VELOCITY PROFILE DEFINITION
less than nominal speed-> +
+--------+ <- nominal_speed /|\
/ \ / | \
entry_speed -> + \ / | + <- next->entry_speed
| + <- next->entry_speed / | |
+-------------+ entry_speed -> +----+--+
time --> ^ ^ ^ ^
| | | |
decelerate distance decelerate distance
Calculates the type of velocity profile for a given planner block and provides the deceleration
distance for the stepper algorithm to use to accurately trace the profile exactly. The planner
computes the entry and exit speeds of each block, but does not bother to determine the details of
the velocity profiles within them, as they aren't needed for computing an optimal plan. When the
stepper algorithm begins to execute a block, the block velocity profiles are computed ad hoc.
Each block velocity profiles can be described as either a trapezoidal or a triangular shape. The
trapezoid occurs when the block reaches the nominal speed of the block and cruises for a period of
time. A triangle occurs when the nominal speed is not reached within the block. Both of these
velocity profiles may also be truncated on either end with no acceleration or deceleration ramps,
as they can be influenced by the conditions of neighboring blocks, where the acceleration ramps
are defined by constant acceleration equal to the maximum allowable acceleration of a block.
Since the stepper algorithm already assumes to begin executing a planner block by accelerating
from the planner entry speed and cruise if the nominal speed is reached, we only need to know
when to begin deceleration to the end of the block. Hence, only the distance from the end of the
block to begin a deceleration ramp is computed for the stepper algorithm when requested.
*/
float plan_calculate_velocity_profile(uint8_t block_index)
{
plan_block_t *current_block = &block_buffer[block_index];
// Determine current block exit speed
float exit_speed_sqr = 0.0; // Initialize for end of planner buffer. Zero speed.
plan_block_t *next_block = plan_get_block_by_index(plan_next_block_index(block_index));
if (next_block != NULL) { exit_speed_sqr = next_block->entry_speed_sqr; } // Exit speed is the entry speed of next buffer block
// First determine intersection distance (in steps) from the exit point for a triangular profile.
// Computes: d_intersect = distance/2 + (v_entry^2-v_exit^2)/(4*acceleration)
float intersect_distance = 0.5*( current_block->millimeters + (current_block->entry_speed_sqr-exit_speed_sqr)/(2*current_block->acceleration) );
// Check if this is a pure acceleration block by a intersection distance less than zero. Also
// prevents signed and unsigned integer conversion errors.
if (intersect_distance > 0 ) {
float decelerate_distance;
// Determine deceleration distance (in steps) from nominal speed to exit speed for a trapezoidal profile.
// Value is never negative. Nominal speed is always greater than or equal to the exit speed.
// Computes: d_decelerate = (v_nominal^2 - v_exit^2)/(2*acceleration)
decelerate_distance = (current_block->nominal_speed_sqr - exit_speed_sqr)/(2*current_block->acceleration);
// The lesser of the two triangle and trapezoid distances always defines the velocity profile.
if (decelerate_distance > intersect_distance) { decelerate_distance = intersect_distance; }
// Finally, check if this is a pure deceleration block.
if (decelerate_distance > current_block->millimeters) { return(0.0); }
else { return( (current_block->millimeters-decelerate_distance) ); }
}
return( current_block->millimeters ); // No deceleration in velocity profile.
}
// 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(int32_t step_events_remaining)
{
plan_block_t *block = &block_buffer[block_buffer_tail]; // Point to partially completed block
// Only remaining millimeters and step_event_count need to be updated for planner recalculate.
// Other variables (step_x, step_y, step_z, rate_delta, etc.) all need to remain the same to
// ensure the original planned motion is resumed exactly.
block->millimeters = (block->millimeters*step_events_remaining)/block->step_event_count;
block->step_event_count = step_events_remaining;
// Re-plan from a complete stop. Reset planner entry speeds and buffer planned pointer.
block->entry_speed_sqr = 0.0;
block->max_entry_speed_sqr = 0.0;
block_buffer_planned = block_buffer_tail;
planner_recalculate();
}
/*
TODO:
When a feed hold or feedrate override is reduced, the velocity profile must execute a
deceleration over the existing plan. By logic, since the plan already decelerates to zero
at the end of the buffer, any replanned deceleration mid-way will never exceed this. It
will only asymptotically approach this in the worst case scenario.
- For a feed hold, we simply need to plan and compute the stopping point within a block
when velocity decelerates to zero. We then can recompute the plan with the already
existing partial block planning code and set the system to a QUEUED state.
- When a feed hold is initiated, the main program should be able to continue doing what
it has been, i.e. arcs, parsing, but needs to be able to reinitialize the plan after
it has come to a stop.
- For a feed rate override (reduce-only), we need to enforce a deceleration until we
intersect the reduced nominal speed of a block after it's been planned with the new
overrides and the newly planned block is accelerating or cruising only. If the new plan
block is decelerating at the intersection point, we keep decelerating until we find a
valid intersection point. Once we find this point, we can then resume onto the new plan,
but we may need to adjust the deceleration point in the intersection block since the
feedrate override could have intersected at an acceleration ramp. This would change the
acceleration ramp to a cruising, so the deceleration point will have changed, but the
plan will have not. It should still be valid for the rest of the buffer. Coding this
can get complicated, but it should be doable. One issue could be is in how to handle
scenarios when a user issues several feedrate overrides and inundates this code. Does
this method still work and is robust enough to compute all of this on the fly? This is
the critical question. However, we could block user input until the planner has time to
catch to solve this as well.
- When the feed rate override increases, we don't have to do anything special. We just
replan the entire buffer with the new nominal speeds and adjust the maximum junction
speeds accordingly.
void plan_compute_deceleration() {
}
void plan_recompute_max_junction_velocity() {
// Assumes the nominal_speed_sqr values have been updated. May need to just multiply
// override values here.
// PROBLEM: Axes-limiting velocities get screwed up. May need to store an int8 value for the
// max override value possible for each block when the line is added. So the nominal_speed
// is computed with that ceiling, but still retained if the rates change again.
uint8_t block_index = block_buffer_tail;
plan_block_t *block = &block_buffer[block_index];
pl.previous_nominal_speed_sqr = block->nominal_speed_sqr;
block_index = plan_next_block_index(block_index);
while (block_index != block_buffer_head) {
block = &block_buffer[block_index];
block->max_entry_speed_sqr = min(block->max_junction_speed_sqr,
min(block->nominal_speed_sqr,pl.previous_nominal_speed_sqr));
pl.previous_nominal_speed_sqr = block->nominal_speed_sqr;
block_index = plan_next_block_index(block_index);
}
}
*/

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@ -1,459 +0,0 @@
/*
planner.c - buffers movement commands and manages the acceleration profile plan
Part of Grbl
Copyright (c) 2011-2013 Sungeun K. Jeon
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/>.
*/
/* The ring buffer implementation gleaned from the wiring_serial library by David A. Mellis. */
#include <inttypes.h>
#include <stdlib.h>
#include "planner.h"
#include "nuts_bolts.h"
#include "stepper.h"
#include "settings.h"
#include "config.h"
#include "protocol.h"
#define SOME_LARGE_VALUE 1.0E+38 // Used by rapids and acceleration maximization calculations. Just needs
// to be larger than any feasible (mm/min)^2 or mm/sec^2 value.
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_sqr; // 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.
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
segment(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);
// Recompute plan only when there is more than one planner block in the buffer. Can't do anything with one.
if (block_index == block_buffer_tail) {
// Just set block_buffer_planned pointer.
block_buffer_planned = block_buffer_tail;
return;
}
// Initialize planner buffer pointers and indexing.
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);
// Reverse Pass: Coarsely maximize all possible deceleration curves back-planning from the last
// block in buffer. Cease planning when: (1) the last optimal planned pointer is reached.
// (2) the safe block pointer is reached, whereby the planned pointer is updated.
// NOTE: Forward pass will later refine and correct the reverse pass to create an optimal plan.
// NOTE: If the safe block is encountered before the planned block pointer, we know the safe block
// will be recomputed within the plan. So, we need to update it if it is partially completed.
float entry_speed_sqr;
plan_block_t *next;
block_index = plan_prev_block_index(block_index);
if (block_index == block_buffer_tail) { // !! OR plan pointer? Yes I think so.
// Only two plannable blocks in buffer. Compute previous block based on
// !!! May only work if a new block is being added. Not for an override. The exit speed isn't zero.
// !!! Need to make the current entry speed calculation after this.
st_update_plan_block_parameters();
block_buffer_planned = block_buffer_tail;
} else {
// Three or more plan-able blocks
while (block_index != block_buffer_planned) {
next = current;
current = &block_buffer[block_index];
// Increment block index early to check if the safe block is before the current block. If encountered,
// this is an exit condition as we can't go further than this block in the reverse pass.
block_index = plan_prev_block_index(block_index);
if (block_index == block_buffer_tail) {
// Check if the safe block is partially completed. If so, update it before its exit speed
// (=current->entry speed) is over-written.
// TODO: The update breaks with feedrate overrides, because the replanning process no longer has
// the previous nominal speed to update this block with. There will need to be something along the
// lines of a nominal speed change check and send the correct value to this function.
st_update_plan_block_parameters();
// Set planned pointer at safe block and for loop exit after following computation is done.
block_buffer_planned = block_buffer_tail;
}
// 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.
// TODO: Need to check if the planned flag logic is correct for all scenarios. It may not
// be for certain conditions. However, if the block reaches nominal speed, it can be a valid
// breakpoint substitute.
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; // Set optimal plan pointer
}
block_index = plan_next_block_index( block_index );
}
}
void plan_init()
{
memset(&pl, 0, sizeof(pl)); // Clear planner struct
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.
block_buffer_tail = plan_next_block_index( block_buffer_tail );
}
}
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()
{
uint8_t block_index = plan_next_block_index(block_buffer_tail);
if (block_index == block_buffer_head) { return( 0.0 ); }
return( sqrt( 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);
}
// Block until all buffered steps are executed or in a cycle state. Works with feed hold
// during a synchronize call, if it should happen. Also, waits for clean cycle end.
void plan_synchronize()
{
while (plan_get_current_block() || sys.state == STATE_CYCLE) {
protocol_execute_runtime(); // Check and execute run-time commands
if (sys.abort) { return; } // Check for system abort
}
}
/* 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). */
void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate)
{
// Prepare and initialize new block
plan_block_t *block = &block_buffer[block_buffer_head];
block->step_event_count = 0;
block->millimeters = 0;
block->direction_bits = 0;
block->acceleration = SOME_LARGE_VALUE; // Scaled down to maximum acceleration later
// Compute and store initial move distance data.
// TODO: After this for-loop, we don't touch the stepper algorithm data. Might be a good idea
// to try to keep these types of things completely separate from the planner for portability.
int32_t target_steps[N_AXIS];
float unit_vec[N_AXIS], delta_mm;
uint8_t idx;
for (idx=0; idx<N_AXIS; idx++) {
// Calculate target position in absolute steps. This conversion should be consistent throughout.
target_steps[idx] = lround(target[idx]*settings.steps_per_mm[idx]);
// Number of steps for each axis and determine max step events
block->steps[idx] = labs(target_steps[idx]-pl.position[idx]);
block->step_event_count = max(block->step_event_count, block->steps[idx]);
// Compute individual axes distance for move and prep unit vector calculations.
// NOTE: Computes true distance from converted step values.
delta_mm = (target_steps[idx] - pl.position[idx])/settings.steps_per_mm[idx];
unit_vec[idx] = delta_mm; // Store unit vector numerator. Denominator computed later.
// Set direction bits. Bit enabled always means direction is negative.
if (delta_mm < 0 ) { block->direction_bits |= get_direction_mask(idx); }
// Incrementally compute total move distance by Euclidean norm. First add square of each term.
block->millimeters += delta_mm*delta_mm;
}
block->millimeters = sqrt(block->millimeters); // Complete millimeters calculation with sqrt()
// Bail if this is a zero-length block. Highly unlikely to occur.
if (block->step_event_count == 0) { return; }
// Adjust feed_rate value to mm/min depending on type of rate input (normal, inverse time, or rapids)
// TODO: Need to distinguish a rapids vs feed move for overrides. Some flag of some sort.
if (feed_rate < 0) { feed_rate = SOME_LARGE_VALUE; } // Scaled down to absolute max/rapids rate later
else if (invert_feed_rate) { feed_rate = block->millimeters/feed_rate; }
// 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.
float inverse_unit_vec_value;
float inverse_millimeters = 1.0/block->millimeters; // Inverse millimeters to remove multiple float divides
float junction_cos_theta = 0;
for (idx=0; idx<N_AXIS; idx++) {
if (unit_vec[idx] != 0) { // Avoid divide by zero.
unit_vec[idx] *= inverse_millimeters; // Complete unit vector calculation
inverse_unit_vec_value = abs(1.0/unit_vec[idx]); // Inverse to remove multiple float divides.
// Check and limit feed rate against max individual axis velocities and accelerations
feed_rate = min(feed_rate,settings.max_velocity[idx]*inverse_unit_vec_value);
block->acceleration = min(block->acceleration,settings.acceleration[idx]*inverse_unit_vec_value);
// Incrementally compute cosine of angle between previous and current path. Cos(theta) of the junction
// between the current move and the previous move is simply the dot product of the two unit vectors,
// where prev_unit_vec is negative. Used later to compute maximum junction speed.
junction_cos_theta -= pl.previous_unit_vec[idx] * unit_vec[idx];
}
}
// TODO: Need to check this method handling zero junction speeds when starting from rest.
if (block_buffer_head == block_buffer_tail) {
// Initialize block entry speed as zero. Assume it will be starting from rest. Planner will correct this later.
block->entry_speed_sqr = 0.0;
block->max_junction_speed_sqr = 0.0; // 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.
*/
// NOTE: Computed without any expensive trig, sin() or acos(), by trig half angle identity of cos(theta).
float sin_theta_d2 = sqrt(0.5*(1.0-junction_cos_theta)); // Trig half angle identity. Always positive.
// TODO: Acceleration used in calculation needs to be limited by the minimum of the two junctions.
block->max_junction_speed_sqr = max( MINIMUM_JUNCTION_SPEED*MINIMUM_JUNCTION_SPEED,
(block->acceleration * settings.junction_deviation * sin_theta_d2)/(1.0-sin_theta_d2) );
}
// Store block nominal speed
block->nominal_speed_sqr = feed_rate*feed_rate; // (mm/min). Always > 0
// Compute the junction maximum entry based on the minimum of the junction speed and neighboring nominal speeds.
block->max_entry_speed_sqr = min(block->max_junction_speed_sqr,
min(block->nominal_speed_sqr,pl.previous_nominal_speed_sqr));
// Update previous path unit_vector and nominal speed (squared)
memcpy(pl.previous_unit_vec, unit_vec, sizeof(unit_vec)); // pl.previous_unit_vec[] = unit_vec[]
pl.previous_nominal_speed_sqr = block->nominal_speed_sqr;
// Update planner position
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();
// int32_t blength = block_buffer_head - block_buffer_tail;
// if (blength < 0) { blength += BLOCK_BUFFER_SIZE; }
// printInteger(blength);
}
// Reset the planner position vectors. Called by the system abort/initialization routine.
void plan_sync_position()
{
uint8_t idx;
for (idx=0; idx<N_AXIS; idx++) {
pl.position[idx] = sys.position[idx];
}
}
// 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(int32_t step_events_remaining)
{
plan_block_t *block = &block_buffer[block_buffer_tail]; // Point to partially completed block
// Only remaining millimeters and step_event_count need to be updated for planner recalculate.
// Other variables (step_x, step_y, step_z, rate_delta, etc.) all need to remain the same to
// ensure the original planned motion is resumed exactly.
block->millimeters = (block->millimeters*step_events_remaining)/block->step_event_count;
block->step_event_count = step_events_remaining;
// Re-plan from a complete stop. Reset planner entry speeds and buffer planned pointer.
block->entry_speed_sqr = 0.0;
block->max_entry_speed_sqr = 0.0;
block_buffer_planned = block_buffer_tail;
planner_recalculate();
}

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archive/planner_v0_9.c
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@ -1,476 +0,0 @@
/*
planner.c - buffers movement commands and manages the acceleration profile plan
Part of Grbl
Copyright (c) 2011-2013 Sungeun K. Jeon
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/>.
*/
/* The ring buffer implementation gleaned from the wiring_serial library by David A. Mellis. */
#include <inttypes.h>
#include <stdlib.h>
#include "planner.h"
#include "nuts_bolts.h"
#include "stepper.h"
#include "settings.h"
#include "config.h"
#include "protocol.h"
#define SOME_LARGE_VALUE 1.0E+38 // Used by rapids and acceleration maximization calculations. Just needs
// to be larger than any feasible (mm/min)^2 or mm/sec^2 value.
static block_t block_buffer[BLOCK_BUFFER_SIZE]; // A ring buffer for motion instructions
static volatile 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_sqr; // Nominal speed of previous path line segment
float last_target[N_AXIS]; // Target position of previous path line segment
} planner_t;
static planner_t pl;
// Returns the index of the next block in the ring buffer
// NOTE: Removed modulo (%) operator, which uses an expensive divide and multiplication.
static uint8_t 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 prev_block_index(uint8_t block_index)
{
if (block_index == 0) { block_index = BLOCK_BUFFER_SIZE; }
block_index--;
return(block_index);
}
/* STEPPER VELOCITY PROFILE DEFINITION
less than nominal rate-> +
+--------+ <- nominal_rate /|\
/ \ / | \
initial_rate -> + \ / | + <- next->initial_rate
| + <- next->initial_rate / | |
+-------------+ initial_rate -> +----+--+
time --> ^ ^ ^ ^
| | | |
decelerate distance decelerate distance
Calculates trapezoid parameters for stepper algorithm. Each block velocity profiles can be
described as either a trapezoidal or a triangular shape. The trapezoid occurs when the block
reaches the nominal speed of the block and cruises for a period of time. A triangle occurs
when the nominal speed is not reached within the block. Some other special cases exist,
such as pure ac/de-celeration velocity profiles from beginning to end or a trapezoid that
has no deceleration period when the next block resumes acceleration.
The following function determines the type of velocity profile and stores the minimum required
information for the stepper algorithm to execute the calculated profiles. In this case, only
the new initial rate and n_steps until deceleration are computed, since the stepper algorithm
already handles acceleration and cruising and just needs to know when to start decelerating.
*/
static void calculate_trapezoid_for_block(block_t *block, float entry_speed_sqr, float exit_speed_sqr)
{
// Compute new initial rate for stepper algorithm
block->initial_rate = ceil(sqrt(entry_speed_sqr)*(INV_TIME_MULTIPLIER/(60*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
// TODO: Compute new nominal rate if a feedrate override occurs.
// block->nominal_rate = ceil(feed_rate*(RANADE_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
// Compute efficiency variable for following calculations. Removes a float divide and multiply.
// TODO: If memory allows, this can be kept in the block buffer since it doesn't change, even after feed holds.
float steps_per_mm_div_2_acc = block->step_event_count/(2*block->acceleration*block->millimeters);
// First determine intersection distance (in steps) from the exit point for a triangular profile.
// Computes: steps_intersect = steps/mm * ( distance/2 + (v_entry^2-v_exit^2)/(4*acceleration) )
int32_t intersect_distance = ceil( 0.5*(block->step_event_count + steps_per_mm_div_2_acc*(entry_speed_sqr-exit_speed_sqr)) );
// Check if this is a pure acceleration block by a intersection distance less than zero. Also
// prevents signed and unsigned integer conversion errors.
if (intersect_distance <= 0) {
block->decelerate_after = 0;
} else {
// Determine deceleration distance (in steps) from nominal speed to exit speed for a trapezoidal profile.
// Value is never negative. Nominal speed is always greater than or equal to the exit speed.
// Computes: steps_decelerate = steps/mm * ( (v_nominal^2 - v_exit^2)/(2*acceleration) )
block->decelerate_after = ceil(steps_per_mm_div_2_acc * (block->nominal_speed_sqr - exit_speed_sqr));
// The lesser of the two triangle and trapezoid distances always defines the velocity profile.
if (block->decelerate_after > intersect_distance) { block->decelerate_after = intersect_distance; }
// Finally, check if this is a pure deceleration block.
if (block->decelerate_after > block->step_event_count) { block->decelerate_after = block->step_event_count; }
}
}
/* PLANNER SPEED DEFINITION
+--------+ <- current->nominal_speed
/ \
current->entry_speed -> + \
| + <- next->entry_speed
+-------------+
time -->
Recalculates the motion plan according to the following algorithm:
1. Go over every block in reverse order and calculate a junction speed reduction (i.e. block_t.entry_speed)
so that:
a. The junction speed is equal to or less than the maximum junction speed limit
b. No speed reduction within one block requires faster deceleration than the acceleration limits.
c. The last (or newest appended) block is planned from a complete stop.
2. Go over every block in chronological (forward) order and dial down junction speed values if
a. The speed increase within one block would require faster acceleration than the acceleration limits.
When these stages are complete, all blocks have a junction entry speed that will allow all speed changes
to be performed using the overall limiting acceleration value, and where no junction speed is greater
than the max limit. In other words, it just computed the fastest possible velocity profile through all
buffered blocks, where the final buffered block is planned to come to a full stop when the buffer is fully
executed. Finally it will:
3. Convert the plan to data that the stepper algorithm needs. Only block trapezoids adjacent to a
a planner-modified junction speed with be updated, the others are assumed ok as is.
All planner computations(1)(2) are performed in floating point to minimize numerical round-off errors. Only
when planned values are converted to stepper rate parameters(3), these are integers. If another motion block
is added while executing, the planner will re-plan and update the stored optimal velocity profile as it goes.
Conceptually, the planner works like blowing up a balloon, where the balloon is the velocity profile. It's
constrained by the speeds at the beginning and end of the buffer, along with the maximum junction speeds and
nominal speeds of each block. Once a plan is computed, or balloon filled, this is the optimal velocity profile
through all of the motions in the buffer. Whenever a new block is added, this changes some of the limiting
conditions, or how the balloon is filled, so it has to be re-calculated to get the new optimal velocity profile.
Also, since the planner only computes on what's in the planner buffer, some motions with lots of short line
segments, like arcs, 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 stop at the end of the
buffer. There are a few simple solutions to this: (1) Maximize the machine acceleration. The planner will be
able to compute higher speed profiles within the same combined distance. (2) Increase line segment(s) distance.
The more combined distance the planner has to use, the faster it can go. (3) Increase the MINIMUM_PLANNER_SPEED.
Not recommended. This will change what speed the planner plans to at the end of the buffer. Can lead to lost
steps when coming to a stop. (4) [BEST] Increase the planner buffer size. The more combined distance, the
bigger the balloon, or faster it can go. But this is not possible for 328p Arduinos because its limited memory
is already maxed out. Future ARM versions should not have this issue, with look-ahead planner blocks numbering
up to a hundred or more.
NOTE: Since this function is constantly re-calculating for every new incoming block, it must be as efficient
as possible. For example, in situations like arc generation or complex curves, the short, rapid line segments
can execute faster than new blocks can be added, and the planner buffer will then starve and empty, leading
to weird hiccup-like jerky motions.
*/
static void planner_recalculate()
{
// Last/newest block in buffer. Exit speed is set with MINIMUM_PLANNER_SPEED. Always recalculated.
uint8_t block_index = block_buffer_head;
block_t *current = &block_buffer[block_index]; // Set as last/newest block in buffer
// Determine safe point for which to plan to.
uint8_t block_buffer_safe = next_block_index( block_buffer_tail );
if (block_buffer_safe == next_buffer_head) { // Only one safe block in buffer to operate on
block_buffer_planned = block_buffer_safe;
calculate_trapezoid_for_block(current, 0.0, MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED);
} else {
// TODO: need to account for the two block condition better. If the currently executing block
// is not safe, do we wait until its done? Can we treat the buffer head differently?
// Calculate trapezoid for the last/newest block.
current->entry_speed_sqr = min( current->max_entry_speed_sqr,
MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED + 2*current->acceleration*current->millimeters);
calculate_trapezoid_for_block(current, current->entry_speed_sqr, MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED);
// Reverse Pass: Back plan the deceleration curve from the last block in buffer. Cease
// planning when: (1) the last optimal planned pointer is reached. (2) the safe block
// pointer is reached, whereby the planned pointer is updated.
float entry_speed_sqr;
block_t *next;
block_index = prev_block_index(block_index);
while (block_index != block_buffer_planned) {
next = current;
current = &block_buffer[block_index];
// Exit loop and update planned pointer when the tail/safe block is reached.
if (block_index == block_buffer_safe) {
block_buffer_planned = block_buffer_safe;
break;
}
// Crudely maximize deceleration curve from the end of the non-optimally planned buffer to
// the optimal plan pointer. Forward pass will adjust and finish optimizing the plan.
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;
}
}
block_index = prev_block_index(block_index);
}
// Forward Pass: Forward plan the acceleration curve from the planned pointer onward.
// Also scans for optimal plan breakpoints and appropriately updates the planned pointer.
block_index = block_buffer_planned; // Begin at buffer planned pointer
next = &block_buffer[prev_block_index(block_buffer_planned)]; // Set up for while loop
while (block_index != next_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) {
block_buffer_planned = block_index;
entry_speed_sqr = current->entry_speed_sqr + 2*current->acceleration*current->millimeters;
if (entry_speed_sqr < next->entry_speed_sqr) {
next->entry_speed_sqr = entry_speed_sqr; // Always <= max_entry_speed_sqr. Backward pass set this.
}
}
// Any block set at its maximum entry speed also creates an optimal plan up to this
// point in the buffer. The optimally planned pointer is updated.
if (next->entry_speed_sqr == next->max_entry_speed_sqr) {
block_buffer_planned = block_index;
}
// Automatically recalculate trapezoid for all buffer blocks from last plan's optimal planned
// pointer to the end of the buffer, except the last block.
calculate_trapezoid_for_block(current, current->entry_speed_sqr, next->entry_speed_sqr);
block_index = next_block_index( block_index );
}
}
}
void plan_init()
{
block_buffer_tail = block_buffer_head;
next_buffer_head = next_block_index(block_buffer_head);
block_buffer_planned = block_buffer_head;
memset(&pl, 0, sizeof(pl)); // Clear planner struct
}
inline void plan_discard_current_block()
{
if (block_buffer_head != block_buffer_tail) {
block_buffer_tail = next_block_index( block_buffer_tail );
}
}
inline block_t *plan_get_current_block()
{
if (block_buffer_head == block_buffer_tail) { return(NULL); }
return(&block_buffer[block_buffer_tail]);
}
// 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);
}
// Block until all buffered steps are executed or in a cycle state. Works with feed hold
// during a synchronize call, if it should happen. Also, waits for clean cycle end.
void plan_synchronize()
{
while (plan_get_current_block() || sys.state == STATE_CYCLE) {
protocol_execute_runtime(); // Check and execute run-time commands
if (sys.abort) { return; } // Check for system abort
}
}
// 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).
void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate)
{
// Prepare and initialize new block
block_t *block = &block_buffer[block_buffer_head];
block->step_event_count = 0;
block->millimeters = 0;
block->direction_bits = 0;
block->acceleration = SOME_LARGE_VALUE; // Scaled down to maximum acceleration later
// Compute and store initial move distance data.
int32_t target_steps[N_AXIS];
float unit_vec[N_AXIS], delta_mm;
uint8_t idx;
for (idx=0; idx<N_AXIS; idx++) {
// Calculate target position in absolute steps
target_steps[idx] = lround(target[idx]*settings.steps_per_mm[idx]);
// Number of steps for each axis and determine max step events
block->steps[idx] = labs(target_steps[idx]-pl.position[idx]);
block->step_event_count = max(block->step_event_count, block->steps[idx]);
// Compute individual axes distance for move and prep unit vector calculations.
delta_mm = target[idx] - pl.last_target[idx];
unit_vec[idx] = delta_mm; // Store unit vector numerator. Denominator computed later.
// Incrementally compute total move distance by Euclidean norm
block->millimeters += delta_mm*delta_mm;
// Set direction bits. Bit enabled always means direction is negative.
if (delta_mm < 0 ) { block->direction_bits |= get_direction_mask(idx); }
}
block->millimeters = sqrt(block->millimeters); // Complete millimeters calculation
// Bail if this is a zero-length block
if (block->step_event_count == 0) { return; }
// Adjust feed_rate value to mm/min depending on type of rate input (normal, inverse time, or rapids)
// TODO: Need to distinguish a rapids vs feed move for overrides. Some flag of some sort.
if (feed_rate < 0) { feed_rate = SOME_LARGE_VALUE; } // Scaled down to absolute max/rapids rate later
else if (invert_feed_rate) { feed_rate = block->millimeters/feed_rate; }
// Calculate the unit vector of the line move and the block maximum feed rate and acceleration limited
// by the maximum possible values. Block rapids rates are computed or feed rates are scaled down so
// they don't exceed the maximum axes velocities. The block acceleration is maximized based on direction
// and axes properties as well.
// 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.
float inverse_unit_vec_value;
float inverse_millimeters = 1.0/block->millimeters; // Inverse millimeters to remove multiple float divides
float junction_cos_theta = 0;
for (idx=0; idx<N_AXIS; idx++) {
if (unit_vec[idx] != 0) { // Avoid divide by zero.
unit_vec[idx] *= inverse_millimeters; // Complete unit vector calculation
inverse_unit_vec_value = abs(1.0/unit_vec[idx]); // Inverse to remove multiple float divides.
// Check and limit feed rate against max individual axis velocities and accelerations
feed_rate = min(feed_rate,settings.max_velocity[idx]*inverse_unit_vec_value);
block->acceleration = min(block->acceleration,settings.acceleration[idx]*inverse_unit_vec_value);
// Incrementally compute cosine of angle between previous and current path. Cos(theta) of the junction
// between the current move and the previous move is simply the dot product of the two unit vectors,
// where prev_unit_vec is negative. Used later to compute maximum junction speed.
junction_cos_theta -= pl.previous_unit_vec[idx] * unit_vec[idx];
}
}
/* 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.
*/
// TODO: Acceleration need to be limited by the minimum of the two junctions.
// TODO: Need to setup a method to handle zero junction speeds when starting from rest.
if (block_buffer_head == block_buffer_tail) {
block->max_entry_speed_sqr = MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED;
} else {
// NOTE: Computed without any expensive trig, sin() or acos(), by trig half angle identity of cos(theta).
float sin_theta_d2 = sqrt(0.5*(1.0-junction_cos_theta)); // Trig half angle identity. Always positive.
block->max_entry_speed_sqr = (block->acceleration * settings.junction_deviation * sin_theta_d2)/(1.0-sin_theta_d2);
}
// Store block nominal speed and rate
block->nominal_speed_sqr = feed_rate*feed_rate; // (mm/min)^2. Always > 0
block->nominal_rate = ceil(feed_rate*(INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
// Compute and store acceleration and distance traveled per step event.
block->rate_delta = ceil(block->acceleration*
((INV_TIME_MULTIPLIER/(60.0*60.0))/(ISR_TICKS_PER_SECOND*ACCELERATION_TICKS_PER_SECOND))); // (mult*mm/isr_tic/accel_tic)
block->d_next = ceil((block->millimeters*INV_TIME_MULTIPLIER)/block->step_event_count); // (mult*mm/step)
// Update previous path unit_vector and nominal speed (squared)
memcpy(pl.previous_unit_vec, unit_vec, sizeof(unit_vec)); // pl.previous_unit_vec[] = unit_vec[]
pl.previous_nominal_speed_sqr = block->nominal_speed_sqr;
// Update planner position
memcpy(pl.position, target_steps, sizeof(target_steps)); // pl.position[] = target_steps[]
memcpy(pl.last_target, target, sizeof(target)); // pl.last_target[] = target[]
planner_recalculate();
// Update buffer head and next buffer head indices.
// NOTE: The buffer head update is atomic since it's one byte. Performed after the new plan
// calculations to help prevent overwriting scenarios with adding a new block to a low buffer.
block_buffer_head = next_buffer_head;
next_buffer_head = next_block_index(block_buffer_head);
}
// Reset the planner position vectors. Called by the system abort/initialization routine.
void plan_sync_position()
{
uint8_t idx;
for (idx=0; idx<N_AXIS; idx++) {
pl.position[idx] = sys.position[idx];
pl.last_target[idx] = sys.position[idx]/settings.steps_per_mm[idx];
}
}
// 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(int32_t step_events_remaining)
{
block_t *block = &block_buffer[block_buffer_tail]; // Point to partially completed block
// Only remaining millimeters and step_event_count need to be updated for planner recalculate.
// Other variables (step_x, step_y, step_z, rate_delta, etc.) all need to remain the same to
// ensure the original planned motion is resumed exactly.
block->millimeters = (block->millimeters*step_events_remaining)/block->step_event_count;
block->step_event_count = step_events_remaining;
// Re-plan from a complete stop. Reset planner entry speeds and buffer planned pointer.
block->entry_speed_sqr = 0.0;
block->max_entry_speed_sqr = MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED;
block_buffer_planned = block_buffer_tail;
planner_recalculate();
}

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/*
planner.h - buffers movement commands and manages the acceleration profile plan
Part of Grbl
Copyright (c) 2011-2013 Sungeun K. Jeon
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 planner_h
#define planner_h
#include "nuts_bolts.h"
// The number of linear motions that can be in the plan at any give time
#ifndef BLOCK_BUFFER_SIZE
#define BLOCK_BUFFER_SIZE 17
#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.
typedef struct {
// Fields used by the bresenham algorithm for tracing the line
uint8_t direction_bits; // The direction bit set for this block (refers to *_DIRECTION_BIT in config.h)
uint32_t steps[N_AXIS]; // Step count along each axis
int32_t step_event_count; // The number of step events required to complete this block
// Fields used by the motion planner to manage acceleration
float nominal_speed_sqr; // Axis-limit adjusted nominal speed for this block in (mm/min)^2
float entry_speed_sqr; // Entry speed at previous-current block junction in (mm/min)^2
float max_entry_speed_sqr; // Maximum allowable junction entry speed in (mm/min)^2
float millimeters; // The total travel of this block in mm
float acceleration; // Axes-limit adjusted line acceleration in mm/min^2
// Settings for the trapezoid generator
uint32_t initial_rate; // The step rate at start of block
int32_t rate_delta; // The steps/minute to add or subtract when changing speed (must be positive)
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
uint32_t d_next; // Scaled distance to next step
} block_t;
// Initialize the motion plan subsystem
void plan_init();
// 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.
void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate);
// Called when the current block is no longer needed. Discards the block and makes the memory
// availible for new blocks.
void plan_discard_current_block();
// Gets the current block. Returns NULL if buffer empty
block_t *plan_get_current_block();
// Reset the planner position vector (in steps)
void plan_sync_position();
// Reinitialize plan with a partially completed block
void plan_cycle_reinitialize(int32_t step_events_remaining);
// 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

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/*
stepper.c - stepper motor driver: executes motion plans using stepper motors
Part of Grbl
Copyright (c) 2011-2013 Sungeun K. Jeon
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/>.
*/
#include <avr/interrupt.h>
#include "stepper.h"
#include "config.h"
#include "settings.h"
#include "planner.h"
#include "nuts_bolts.h"
// Some useful constants
#define TICKS_PER_MICROSECOND (F_CPU/1000000)
#define RAMP_NOOP_CRUISE 0
#define RAMP_ACCEL 1
#define RAMP_DECEL 2
#define LOAD_NOOP 0
#define LOAD_SEGMENT 1
#define LOAD_BLOCK 2
#define SEGMENT_NOOP 0
#define SEGMENT_END_OF_BLOCK bit(0)
#define RAMP_CHANGE_ACCEL bit(1)
#define RAMP_CHANGE_DECEL bit(2)
#define MINIMUM_STEPS_PER_SEGMENT 1 // Don't change
#define SEGMENT_BUFFER_SIZE 6
// Stepper state variable. Contains running data and trapezoid variables.
typedef struct {
// Used by the bresenham line algorithm
int32_t counter_x, // Counter variables for the bresenham line tracer
counter_y,
counter_z;
uint8_t segment_steps_remaining; // Steps remaining in line segment motion
// Used by inverse time algorithm to track step rate
int32_t counter_dist; // Inverse time distance traveled since last step event
uint32_t ramp_rate; // Inverse time distance traveled per interrupt tick
uint32_t dist_per_tick;
// Used by the stepper driver interrupt
uint8_t execute_step; // Flags step execution for each interrupt.
uint8_t step_pulse_time; // Step pulse reset time after step rise
uint8_t out_bits; // The next stepping-bits to be output
uint8_t load_flag;
uint8_t counter_ramp;
uint8_t ramp_type;
} stepper_t;
static stepper_t st;
// Stores stepper common data for executing steps in the segment buffer. Data can change mid-block when the
// planner updates the remaining block velocity profile with a more optimal plan or a feedrate override occurs.
// NOTE: Normally, this buffer is partially in-use, but, for the worst case scenario, it will never exceed
// the number of accessible stepper buffer segments (SEGMENT_BUFFER_SIZE-1).
typedef struct {
int32_t step_events_remaining; // Tracks step event count for the executing planner block
uint32_t dist_per_step; // Scaled distance to next step
uint32_t initial_rate; // Initialized step rate at re/start of a planner block
uint32_t nominal_rate; // The nominal step rate for this block in step_events/minute
uint32_t rate_delta; // The steps/minute to add or subtract when changing speed (must be positive)
uint32_t current_approx_rate; // Tracks the approximate segment rate to predict steps per segment to execute
int32_t decelerate_after; // Tracks when to initiate deceleration according to the planner block
float mm_per_step;
} st_data_t;
static st_data_t segment_data[SEGMENT_BUFFER_SIZE-1];
// Primary stepper segment ring buffer. Contains small, short line segments for the stepper algorithm to execute,
// which are "checked-out" incrementally from the first block in the planner buffer. Once "checked-out", the steps
// in the segments buffer cannot be modified by the planner, where the remaining planner block steps still can.
typedef struct {
uint8_t n_step; // Number of step events to be executed for this segment
uint8_t st_data_index; // Stepper buffer common data index. Uses this information to execute this segment.
uint8_t flag; // Stepper algorithm bit-flag for special execution conditions.
} st_segment_t;
static st_segment_t segment_buffer[SEGMENT_BUFFER_SIZE];
// Step segment ring buffer indices
static volatile uint8_t segment_buffer_tail;
static volatile uint8_t segment_buffer_head;
static uint8_t segment_next_head;
static volatile uint8_t busy; // Used to avoid ISR nesting of the "Stepper Driver Interrupt". Should never occur though.
static plan_block_t *pl_current_block; // A pointer to the planner block currently being traced
static st_segment_t *st_current_segment;
static st_data_t *st_current_data;
// Pointers for the step segment being prepped from the planner buffer. Accessed only by the
// main program. Pointers may be planning segments or planner blocks ahead of what being executed.
static plan_block_t *pl_prep_block; // Pointer to the planner block being prepped
static st_data_t *st_prep_data; // Pointer to the stepper common data being prepped
static uint8_t pl_prep_index; // Index of planner block being prepped
static uint8_t st_data_prep_index; // Index of stepper common data block being prepped
static uint8_t pl_partial_block_flag; // Flag indicating the planner has modified the prepped planner block
/* __________________________
/| |\ _________________ ^
/ | | \ /| |\ |
/ | | \ / | | \ s
/ | | | | | \ p
/ | | | | | \ e
+-----+------------------------+---+--+---------------+----+ e
| BLOCK 1 | BLOCK 2 | d
time ----->
The trapezoid is the shape the speed curve over time. It starts at block->initial_rate, accelerates by block->rate_delta
until reaching cruising speed block->nominal_rate, and/or until step_events_remaining reaches block->decelerate_after
after which it decelerates until the block is completed. The driver uses constant acceleration, which is applied as
+/- block->rate_delta velocity increments by the midpoint rule at each ACCELERATION_TICKS_PER_SECOND.
*/
// Stepper state initialization. Cycle should only start if the st.cycle_start flag is
// enabled. Startup init and limits call this function but shouldn't start the cycle.
void st_wake_up()
{
// Enable steppers by resetting the stepper disable port
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
}
if (sys.state == STATE_CYCLE) {
// Initialize stepper output bits
st.out_bits = settings.invert_mask;
// Initialize step pulse timing from settings.
st.step_pulse_time = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND) >> 3);
// Enable stepper driver interrupt
st.execute_step = false;
st.load_flag = LOAD_BLOCK;
TCNT2 = 0; // Clear Timer2
TIMSK2 |= (1<<OCIE2A); // Enable Timer2 Compare Match A interrupt
TCCR2B = (1<<CS21); // Begin Timer2. Full speed, 1/8 prescaler
}
}
// Stepper shutdown
void st_go_idle()
{
// Disable stepper driver interrupt. Allow Timer0 to finish. It will disable itself.
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt
TCCR2B = 0; // Disable Timer2
busy = false;
// Disable steppers only upon system alarm activated or by user setting to not be kept enabled.
if ((settings.stepper_idle_lock_time != 0xff) || bit_istrue(sys.execute,EXEC_ALARM)) {
// Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
// stop and not drift from residual inertial forces at the end of the last movement.
delay_ms(settings.stepper_idle_lock_time);
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
}
}
}
/* "The Stepper Driver Interrupt" - This timer interrupt is the workhorse of Grbl. It is based
on an inverse time stepper algorithm, where a timer ticks at a constant frequency and uses
time-distance counters to track when its the approximate time for a step event. For reference,
a similar inverse-time algorithm by Pramod Ranade is susceptible to numerical round-off, as
described, meaning that some axes steps may not execute correctly for a given multi-axis motion.
Grbl's algorithm differs by using a single inverse time-distance counter to manage a
Bresenham line algorithm for multi-axis step events, which ensures the number of steps for
each axis are executed exactly. In other words, Grbl uses a Bresenham within a Bresenham
algorithm, where one tracks time for step events and the other steps for multi-axis moves.
Grbl specifically uses the Bresenham algorithm due to its innate mathematical exactness and
low computational overhead, requiring simple integer +,- counters only.
This interrupt pops blocks from the step segment buffer and executes them by pulsing the
stepper pins appropriately. It is supported by The Stepper Port Reset Interrupt which it uses
to reset the stepper port after each pulse. The bresenham line tracer algorithm controls all
three stepper outputs simultaneously with these two interrupts.
*/
/* TODO:
- Measure time in ISR. Typical and worst-case. Should be virtually identical to last algorithm.
There are no major changes to the base operations of this ISR with the new segment buffer.
- Write how the acceleration counters work and why they are set at half via mid-point rule.
- Determine if placing the position counters elsewhere (or change them to 8-bit variables that
are added to the system position counters at the end of a segment) frees up cycles.
- Write a blurb about how the acceleration should be handled within the ISR. All of the
time/step/ramp counters accurately keep track of the remainders and phasing of the variables
with time. This means we do not have to compute them via expensive floating point beforehand.
- Need to do an analysis to determine if these counters are really that much cheaper. At least
find out when it isn't anymore. Particularly when the ISR is at a very high frequency.
- Create NOTE: to describe that the total time in this ISR must be less than the ISR frequency
in its worst case scenario.
*/
ISR(TIMER2_COMPA_vect)
{
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
if (busy) { return; } // The busy-flag is used to avoid reentering this interrupt
// Pulse stepper port pins, if flagged. New block dir will always be set one timer tick
// before any step pulse due to algorithm design.
if (st.execute_step) {
st.execute_step = false;
STEPPING_PORT = ( STEPPING_PORT & ~(DIRECTION_MASK | STEP_MASK) ) | st.out_bits;
TCNT0 = st.step_pulse_time; // Reload Timer0 counter.
TCCR0B = (1<<CS21); // Begin Timer0. Full speed, 1/8 prescaler
}
busy = true;
sei(); // Re-enable interrupts to allow Stepper Port Reset Interrupt to fire on-time.
// NOTE: The remaining code in this ISR will finish before returning to main program.
// If there is no step segment, attempt to pop one from the stepper buffer
if (st.load_flag != LOAD_NOOP) {
// Anything in the buffer? If so, load and initialize next step segment.
if (segment_buffer_head != segment_buffer_tail) {
// Initialize new step segment and load number of steps to execute
st_current_segment = &segment_buffer[segment_buffer_tail];
st.segment_steps_remaining = st_current_segment->n_step;
// If the new segment starts a new planner block, initialize stepper variables and counters.
// NOTE: For new segments only, the step counters are not updated to ensure step phasing is continuous.
if (st.load_flag == LOAD_BLOCK) {
pl_current_block = plan_get_current_block(); // Should always be there. Stepper buffer handles this.
st_current_data = &segment_data[segment_buffer[segment_buffer_tail].st_data_index];
// Initialize direction bits for block. Set execute flag to set directions bits upon next ISR tick.
st.out_bits = pl_current_block->direction_bits ^ settings.invert_mask;
st.execute_step = true;
// Initialize Bresenham line counters
st.counter_x = (pl_current_block->step_event_count >> 1);
st.counter_y = st.counter_x;
st.counter_z = st.counter_x;
// Initialize inverse time, step rate data, and acceleration ramp counters
st.counter_dist = st_current_data->dist_per_step; // dist_per_step always greater than ramp_rate.
st.ramp_rate = st_current_data->initial_rate;
st.counter_ramp = ISR_TICKS_PER_ACCELERATION_TICK/2; // Initialize ramp counter via midpoint rule
st.ramp_type = RAMP_NOOP_CRUISE; // Initialize as no ramp operation. Corrected later if necessary.
// Ensure the initial step rate exceeds the MINIMUM_STEP_RATE.
if (st.ramp_rate < MINIMUM_STEP_RATE) { st.dist_per_tick = MINIMUM_STEP_RATE; }
else { st.dist_per_tick = st.ramp_rate; }
}
// Check if ramp conditions have changed. If so, update ramp counters and control variables.
if ( st_current_segment->flag & (RAMP_CHANGE_DECEL | RAMP_CHANGE_ACCEL) ) {
/* Compute correct ramp count for a ramp change. Upon a switch from acceleration to deceleration,
or vice-versa, the new ramp count must be set to trigger the next acceleration tick equal to
the number of ramp ISR ticks counted since the last acceleration tick. This is ensures the
ramp is executed exactly as the plan dictates. Otherwise, when a ramp begins from a known
rate (nominal/cruise or initial), the ramp count must be set to ISR_TICKS_PER_ACCELERATION_TICK/2
as mandated by the mid-point rule. For the latter conditions, the ramp count have been
initialized such that the following computation is still correct. */
st.counter_ramp = ISR_TICKS_PER_ACCELERATION_TICK-st.counter_ramp;
if ( st_current_segment->flag & RAMP_CHANGE_DECEL ) { st.ramp_type = RAMP_DECEL; }
else { st.ramp_type = RAMP_ACCEL; }
}
st.load_flag = LOAD_NOOP; // Segment motion loaded. Set no-operation flag to skip during execution.
} else {
// Can't discard planner block here if a feed hold stops in middle of block.
st_go_idle();
bit_true(sys.execute,EXEC_CYCLE_STOP); // Flag main program for cycle end
return; // Nothing to do but exit.
}
}
// Adjust inverse time counter for ac/de-celerations
if (st.ramp_type) { // Ignored when ramp type is RAMP_NOOP_CRUISE
st.counter_ramp--; // Tick acceleration ramp counter
if (st.counter_ramp == 0) { // Adjust step rate when its time
st.counter_ramp = ISR_TICKS_PER_ACCELERATION_TICK; // Reload ramp counter
if (st.ramp_type == RAMP_ACCEL) { // Adjust velocity for acceleration
st.ramp_rate += st_current_data->rate_delta;
if (st.ramp_rate >= st_current_data->nominal_rate) { // Reached nominal rate.
st.ramp_rate = st_current_data->nominal_rate; // Set cruising velocity
st.ramp_type = RAMP_NOOP_CRUISE; // Set ramp flag to cruising
st.counter_ramp = ISR_TICKS_PER_ACCELERATION_TICK/2; // Re-initialize counter for next ramp change.
}
} else { // Adjust velocity for deceleration.
if (st.ramp_rate > st_current_data->rate_delta) {
st.ramp_rate -= st_current_data->rate_delta;
} else { // Moving near zero feed rate. Gracefully slow down.
st.ramp_rate >>= 1; // Integer divide by 2 until complete. Also prevents overflow.
}
}
// Adjust for minimum step rate, but retain operating ramp rate for accurate velocity tracing.
if (st.ramp_rate < MINIMUM_STEP_RATE) { st.dist_per_tick = MINIMUM_STEP_RATE; }
else { st.dist_per_tick = st.ramp_rate; }
}
}
// Iterate inverse time counter. Triggers each Bresenham step event.
st.counter_dist -= st.dist_per_tick;
// Execute Bresenham step event, when it's time to do so.
if (st.counter_dist < 0) {
st.counter_dist += st_current_data->dist_per_step; // Reload inverse time counter
st.out_bits = pl_current_block->direction_bits; // Reset out_bits and reload direction bits
st.execute_step = true;
// Execute step displacement profile by Bresenham line algorithm
st.counter_x -= pl_current_block->steps[X_AXIS];
if (st.counter_x < 0) {
st.out_bits |= (1<<X_STEP_BIT);
st.counter_x += pl_current_block->step_event_count;
if (st.out_bits & (1<<X_DIRECTION_BIT)) { sys.position[X_AXIS]--; }
else { sys.position[X_AXIS]++; }
}
st.counter_y -= pl_current_block->steps[Y_AXIS];
if (st.counter_y < 0) {
st.out_bits |= (1<<Y_STEP_BIT);
st.counter_y += pl_current_block->step_event_count;
if (st.out_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS]--; }
else { sys.position[Y_AXIS]++; }
}
st.counter_z -= pl_current_block->steps[Z_AXIS];
if (st.counter_z < 0) {
st.out_bits |= (1<<Z_STEP_BIT);
st.counter_z += pl_current_block->step_event_count;
if (st.out_bits & (1<<Z_DIRECTION_BIT)) { sys.position[Z_AXIS]--; }
else { sys.position[Z_AXIS]++; }
}
// Check step events for trapezoid change or end of block.
st.segment_steps_remaining--; // Decrement step events count
if (st.segment_steps_remaining == 0) {
// Line move is complete, set load line flag to check for new move.
// Check if last line move in planner block. Discard if so.
if (st_current_segment->flag & SEGMENT_END_OF_BLOCK) {
plan_discard_current_block();
st.load_flag = LOAD_BLOCK;
} else {
st.load_flag = LOAD_SEGMENT;
}
// Discard current segment by advancing buffer tail index
if ( ++segment_buffer_tail == SEGMENT_BUFFER_SIZE) { segment_buffer_tail = 0; }
}
st.out_bits ^= settings.invert_mask; // Apply step port invert mask
}
busy = false;
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
}
// The Stepper Port Reset Interrupt: Timer0 OVF interrupt handles the falling edge of the step
// pulse. This should always trigger before the next Timer2 COMPA interrupt and independently
// finish, if Timer2 is disabled after completing a move.
ISR(TIMER0_OVF_vect)
{
STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | (settings.invert_mask & STEP_MASK);
TCCR0B = 0; // Disable timer until needed.
}
// Reset and clear stepper subsystem variables
void st_reset()
{
memset(&st, 0, sizeof(st));
st.load_flag = LOAD_BLOCK;
busy = false;
pl_current_block = NULL; // Planner block pointer used by stepper algorithm
pl_prep_block = NULL; // Planner block pointer used by segment buffer
pl_prep_index = 0; // Planner buffer indices are also reset to zero.
st_data_prep_index = 0;
segment_buffer_tail = 0;
segment_buffer_head = 0; // empty = tail
segment_next_head = 1;
pl_partial_block_flag = false;
}
// Initialize and start the stepper motor subsystem
void st_init()
{
// Configure directions of interface pins
STEPPING_DDR |= STEPPING_MASK;
STEPPING_PORT = (STEPPING_PORT & ~STEPPING_MASK) | settings.invert_mask;
STEPPERS_DISABLE_DDR |= 1<<STEPPERS_DISABLE_BIT;
// Configure Timer 2
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt while configuring it
TCCR2B = 0; // Disable Timer2 until needed
TCNT2 = 0; // Clear Timer2 counter
TCCR2A = (1<<WGM21); // Set CTC mode
OCR2A = (F_CPU/ISR_TICKS_PER_SECOND)/8 - 1; // Set Timer2 CTC rate
// Configure Timer 0
TIMSK0 &= ~(1<<TOIE0);
TCCR0A = 0; // Normal operation
TCCR0B = 0; // Disable Timer0 until needed
TIMSK0 |= (1<<TOIE0); // Enable overflow interrupt
// Start in the idle state, but first wake up to check for keep steppers enabled option.
st_wake_up();
st_go_idle();
}
// Planner external interface to start stepper interrupt and execute the blocks in queue. Called
// by the main program functions: planner auto-start and run-time command execution.
void st_cycle_start()
{
if (sys.state == STATE_QUEUED) {
sys.state = STATE_CYCLE;
st_prep_buffer(); // Initialize step segment buffer before beginning cycle.
st_wake_up();
}
}
// Execute a feed hold with deceleration, only during cycle. Called by main program.
void st_feed_hold()
{
if (sys.state == STATE_CYCLE) {
sys.state = STATE_HOLD;
sys.auto_start = false; // Disable planner auto start upon feed hold.
}
}
// Reinitializes the cycle plan and stepper system after a feed hold for a resume. Called by
// runtime command execution in the main program, ensuring that the planner re-plans safely.
// NOTE: Bresenham algorithm variables are still maintained through both the planner and stepper
// cycle reinitializations. The stepper path should continue exactly as if nothing has happened.
// Only the planner de/ac-celerations profiles and stepper rates have been updated.
void st_cycle_reinitialize()
{
// if (pl_current_block != NULL) {
// Replan buffer from the feed hold stop location.
// TODO: Need to add up all of the step events in the current planner block to give
// back to the planner. Should only need it for the current block.
// BUT! The planner block millimeters is all changed and may be changed into the next
// planner block. The block millimeters would need to be recalculated via step counts
// and the mm/step variable.
// OR. Do we plan the feed hold itself down with the planner.
// plan_cycle_reinitialize(st_current_data->step_events_remaining);
// st.ramp_type = RAMP_ACCEL;
// st.counter_ramp = ISR_TICKS_PER_ACCELERATION_TICK/2;
// st.ramp_rate = 0;
// sys.state = STATE_QUEUED;
// } else {
// sys.state = STATE_IDLE;
// }
sys.state = STATE_IDLE;
}
/* Prepares step segment buffer. Continuously called from main program.
The segment buffer is an intermediary buffer interface between the execution of steps
by the stepper algorithm and the velocity profiles generated by the planner. The stepper
algorithm only executes steps within the segment buffer and is filled by the main program
when steps are "checked-out" from the first block in the planner buffer. This keeps the
step execution and planning optimization processes atomic and protected from each other.
The number of steps "checked-out" from the planner buffer and the number of segments in
the segment buffer is sized and computed such that no operation in the main program takes
longer than the time it takes the stepper algorithm to empty it before refilling it.
Currently, the segment buffer conservatively holds roughly up to 40-60 msec of steps.
NOTE: The segment buffer executes a set number of steps over an approximate time period.
If we try to execute over a fixed time period, it is difficult to guarantee or predict
how many steps will execute over it, especially when the step pulse phasing between the
neighboring segments must also be kept consistent. Meaning that, if the last segment step
pulses right before a segment end, the next segment must delay its first pulse so that the
step pulses are consistently spaced apart over time to keep the step pulse train nice and
smooth. Keeping track of phasing and ensuring that the exact number of steps are executed
as defined by the planner block, the related computational overhead can get quickly and
prohibitively expensive, especially in real-time.
Since the stepper algorithm automatically takes care of the step pulse phasing with
its ramp and inverse time counters by retaining the count remainders, we don't have to
explicitly and expensively track and synchronize the exact number of steps, time, and
phasing of steps. All we need to do is approximate the number of steps in each segment
such that the segment buffer has enough execution time for the main program to do what
it needs to do and refill it when it comes back. In other words, we just need to compute
a cheap approximation of the current velocity and the number of steps over it.
*/
/*
TODO: Figure out how to enforce a deceleration when a feedrate override is reduced.
The problem is that when an override is reduced, the planner may not plan back to
the current rate. Meaning that the velocity profiles for certain conditions no longer
are trapezoidal or triangular. For example, if the current block is cruising at a
nominal rate and the feedrate override is reduced, the new nominal rate will now be
lower. The velocity profile must first decelerate to the new nominal rate and then
follow on the new plan. So the remaining velocity profile will have a decelerate,
cruise, and another decelerate.
Another issue is whether or not a feedrate override reduction causes a deceleration
that acts over several planner blocks. For example, say that the plan is already
heavily decelerating throughout it, reducing the feedrate will not do much to it. So,
how do we determine when to resume the new plan? How many blocks do we have to wait
until the new plan intersects with the deceleration curve? One plus though, the
deceleration will never be more than the number of blocks in the entire planner buffer,
but it theoretically can be equal to it when all planner blocks are decelerating already.
*/
void st_prep_buffer()
{
if (sys.state == STATE_QUEUED) { return; } // Block until a motion state is issued
while (segment_buffer_tail != segment_next_head) { // Check if we need to fill the buffer.
// Initialize new segment
st_segment_t *prep_segment = &segment_buffer[segment_buffer_head];
prep_segment->flag = SEGMENT_NOOP;
// Determine if we need to load a new planner block.
if (pl_prep_block == NULL) {
pl_prep_block = plan_get_block_by_index(pl_prep_index); // Query planner for a queued block
if (pl_prep_block == NULL) { return; } // No planner blocks. Exit.
SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
// Increment stepper common data index
if ( ++st_data_prep_index == (SEGMENT_BUFFER_SIZE-1) ) { st_data_prep_index = 0; }
// Check if the planner has re-computed this block mid-execution. If so, push the previous segment
// data. Otherwise, prepare a new segment data for the new planner block.
if (pl_partial_block_flag) {
// Prepare new shared segment block data and copy the relevant last segment block data.
st_data_t *last_st_prep_data;
last_st_prep_data = st_prep_data;
st_prep_data = &segment_data[st_data_prep_index];
st_prep_data->step_events_remaining = last_st_prep_data->step_events_remaining;
st_prep_data->rate_delta = last_st_prep_data->rate_delta;
st_prep_data->dist_per_step = last_st_prep_data->dist_per_step;
st_prep_data->nominal_rate = last_st_prep_data->nominal_rate; // TODO: Feedrate overrides recomputes this.
st_prep_data->mm_per_step = last_st_prep_data->mm_per_step;
pl_partial_block_flag = false; // Reset flag
} else {
// Prepare commonly shared planner block data for the ensuing segment buffer moves ad-hoc, since
// the planner buffer can dynamically change the velocity profile data as blocks are added.
st_prep_data = &segment_data[st_data_prep_index];
// Initialize Bresenham variables
st_prep_data->step_events_remaining = pl_prep_block->step_event_count;
// Convert planner block velocity profile data to stepper rate and step distance data.
st_prep_data->nominal_rate = ceil(sqrt(pl_prep_block->nominal_speed_sqr)*(INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
st_prep_data->rate_delta = ceil(pl_prep_block->acceleration*
((INV_TIME_MULTIPLIER/(60.0*60.0))/(ISR_TICKS_PER_SECOND*ACCELERATION_TICKS_PER_SECOND))); // (mult*mm/isr_tic/accel_tic)
st_prep_data->dist_per_step = ceil((pl_prep_block->millimeters*INV_TIME_MULTIPLIER)/pl_prep_block->step_event_count); // (mult*mm/step)
// TODO: Check if we really need to store this.
st_prep_data->mm_per_step = pl_prep_block->millimeters/pl_prep_block->step_event_count;
}
// Convert planner entry speed to stepper initial rate.
st_prep_data->initial_rate = ceil(sqrt(pl_prep_block->entry_speed_sqr)*(INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
// TODO: Nominal rate changes with feedrate override.
// st_prep_data->nominal_rate = ceil(sqrt(pl_prep_block->nominal_speed_sqr)*(INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
st_prep_data->current_approx_rate = st_prep_data->initial_rate;
// Calculate the planner block velocity profile type, determine deceleration point, and initial ramp.
float mm_decelerate_after = plan_calculate_velocity_profile(pl_prep_index);
st_prep_data->decelerate_after = ceil( mm_decelerate_after/st_prep_data->mm_per_step );
if (st_prep_data->decelerate_after > 0) { // If 0, RAMP_CHANGE_DECEL flag is set later.
if (st_prep_data->initial_rate != st_prep_data->nominal_rate) { prep_segment->flag = RAMP_CHANGE_ACCEL; }
}
}
// Set new segment to point to the current segment data block.
prep_segment->st_data_index = st_data_prep_index;
// Approximate the velocity over the new segment using the already computed rate values.
// NOTE: This assumes that each segment will have an execution time roughly equal to every ACCELERATION_TICK.
// We do this to minimize memory and computational requirements. However, this could easily be replaced with
// a more exact approximation or have an user-defined time per segment, if CPU and memory overhead allows.
if (st_prep_data->decelerate_after <= 0) {
if (st_prep_data->decelerate_after == 0) { prep_segment->flag = RAMP_CHANGE_DECEL; } // Set segment deceleration flag
else { st_prep_data->current_approx_rate -= st_prep_data->rate_delta; }
if (st_prep_data->current_approx_rate < st_prep_data->rate_delta) { st_prep_data->current_approx_rate >>= 1; }
} else {
if (st_prep_data->current_approx_rate < st_prep_data->nominal_rate) {
st_prep_data->current_approx_rate += st_prep_data->rate_delta;
if (st_prep_data->current_approx_rate > st_prep_data->nominal_rate) {
st_prep_data->current_approx_rate = st_prep_data->nominal_rate;
}
}
}
// TODO: Look into replacing the following dist_per_step divide with multiplying its inverse to save cycles.
// Compute the number of steps in the prepped segment based on the approximate current rate.
// NOTE: The dist_per_step divide cancels out the INV_TIME_MULTIPLIER and converts the rate value to steps.
prep_segment->n_step = ceil(max(MINIMUM_STEP_RATE,st_prep_data->current_approx_rate)*
(ISR_TICKS_PER_SECOND/ACCELERATION_TICKS_PER_SECOND)/st_prep_data->dist_per_step);
// NOTE: Ensures it moves for very slow motions, but MINIMUM_STEP_RATE should always set this too. Perhaps
// a compile-time check to see if MINIMUM_STEP_RATE is set high enough is all that is needed.
prep_segment->n_step = max(prep_segment->n_step,MINIMUM_STEPS_PER_SEGMENT);
// NOTE: As long as the ACCELERATION_TICKS_PER_SECOND is valid, n_step should never exceed 255 and overflow.
// prep_segment->n_step = min(prep_segment->n_step,MAXIMUM_STEPS_PER_BLOCK); // Prevent unsigned int8 overflow.
// Check if n_step exceeds steps remaining in planner block. If so, truncate.
if (prep_segment->n_step > st_prep_data->step_events_remaining) {
prep_segment->n_step = st_prep_data->step_events_remaining;
}
// Check if n_step crosses decelerate point in block. If so, truncate to ensure the deceleration
// ramp counters are set correctly during execution.
if (st_prep_data->decelerate_after > 0) {
if (prep_segment->n_step > st_prep_data->decelerate_after) {
prep_segment->n_step = st_prep_data->decelerate_after;
}
}
// Update stepper common data variables.
st_prep_data->decelerate_after -= prep_segment->n_step;
st_prep_data->step_events_remaining -= prep_segment->n_step;
// Check for end of planner block
if ( st_prep_data->step_events_remaining == 0 ) {
// TODO: When a feed hold ends, the step_events_remaining will also be zero, even though a block
// have partially been completed. We need to flag the stepper algorithm to indicate a stepper shutdown
// when complete, but not remove the planner block unless it truly is the end of the block (rare).
// Set EOB bitflag so stepper algorithm discards the planner block after this segment completes.
prep_segment->flag |= SEGMENT_END_OF_BLOCK;
// Move planner pointer to next block and flag to load a new block for the next segment.
pl_prep_index = plan_next_block_index(pl_prep_index);
pl_prep_block = NULL;
}
// New step segment completed. Increment segment buffer indices.
segment_buffer_head = segment_next_head;
if ( ++segment_next_head == SEGMENT_BUFFER_SIZE ) { segment_next_head = 0; }
// long a = prep_segment->n_step;
// printInteger(a);
// printString(" ");
SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
}
}
uint8_t st_get_prep_block_index()
{
// Returns only the index but doesn't state if the block has been partially executed. How do we simply check for this?
return(pl_prep_index);
}
void st_fetch_partial_block_parameters(uint8_t block_index, float *millimeters_remaining, uint8_t *is_decelerating)
{
// if called, can we assume that this always changes and needs to be updated? if so, then
// we can perform all of the segment buffer setup tasks here to make sure the next time
// the segments are loaded, the st_data buffer is updated correctly.
// !!! Make sure that this is always pointing to the correct st_prep_data block.
// When a mid-block acceleration occurs, we have to make sure the ramp counters are updated
// correctly, much in the same fashion as the deceleration counters. Need to think about this
// make sure this is right, but i'm pretty sure it is.
// TODO: NULL means that the segment buffer has just completed a planner block. Clean up!
if (pl_prep_block != NULL) {
*millimeters_remaining = st_prep_data->step_events_remaining*st_prep_data->mm_per_step;
if (st_prep_data->decelerate_after > 0) { *is_decelerating = false; }
else { *is_decelerating = true; }
// Flag for new prep_block when st_prep_buffer() is called after the planner recomputes.
pl_partial_block_flag = true;
pl_prep_block = NULL;
}
return;
}

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@ -1,746 +0,0 @@
/*
stepper.c - stepper motor driver: executes motion plans using stepper motors
Part of Grbl
Copyright (c) 2011-2013 Sungeun K. Jeon
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/>.
*/
#include <avr/interrupt.h>
#include "stepper.h"
#include "config.h"
#include "settings.h"
#include "planner.h"
#include "nuts_bolts.h"
// Some useful constants
#define TICKS_PER_MICROSECOND (F_CPU/1000000)
#define RAMP_NOOP_CRUISE 0
#define RAMP_ACCEL 1
#define RAMP_DECEL 2
#define LOAD_NOOP 0
#define LOAD_SEGMENT 1
#define LOAD_BLOCK 2
#define SEGMENT_NOOP 0
#define SEGMENT_END_OF_BLOCK bit(0)
#define SEGMENT_ACCEL bit(1)
#define SEGMENT_DECEL bit(2)
#define MINIMUM_STEPS_PER_SEGMENT 1 // Don't change
#define SEGMENT_BUFFER_SIZE 6
// Stepper state variable. Contains running data and trapezoid variables.
typedef struct {
// Used by the bresenham line algorithm
int32_t counter_x, // Counter variables for the bresenham line tracer
counter_y,
counter_z;
uint8_t segment_steps_remaining; // Steps remaining in line segment motion
// Used by inverse time algorithm to track step rate
int32_t counter_d; // Inverse time distance traveled since last step event
uint32_t delta_d; // Inverse time distance traveled per interrupt tick
uint32_t d_per_tick;
// Used by the stepper driver interrupt
uint8_t execute_step; // Flags step execution for each interrupt.
uint8_t step_pulse_time; // Step pulse reset time after step rise
uint8_t out_bits; // The next stepping-bits to be output
uint8_t load_flag;
uint8_t ramp_count;
uint8_t ramp_type;
} stepper_t;
static stepper_t st;
// Stores stepper common data for executing steps in the segment buffer. Data can change mid-block when the
// planner updates the remaining block velocity profile with a more optimal plan or a feedrate override occurs.
// NOTE: Normally, this buffer is partially in-use, but, for the worst case scenario, it will never exceed
// the number of accessible stepper buffer segments (SEGMENT_BUFFER_SIZE-1).
typedef struct {
int32_t step_events_remaining; // Tracks step event count for the executing planner block
uint32_t d_next; // Scaled distance to next step
uint32_t initial_rate; // Initialized step rate at re/start of a planner block
uint32_t nominal_rate; // The nominal step rate for this block in step_events/minute
uint32_t rate_delta; // The steps/minute to add or subtract when changing speed (must be positive)
uint32_t current_approx_rate; // Tracks the approximate segment rate to predict steps per segment to execute
int32_t decelerate_after; // Tracks when to initiate deceleration according to the planner block
float mm_per_step;
} st_data_t;
static st_data_t segment_data[SEGMENT_BUFFER_SIZE-1];
// Primary stepper segment ring buffer. Contains small, short line segments for the stepper algorithm to execute,
// which are "checked-out" incrementally from the first block in the planner buffer. Once "checked-out", the steps
// in the segments buffer cannot be modified by the planner, where the remaining planner block steps still can.
typedef struct {
uint8_t n_step; // Number of step events to be executed for this segment
uint8_t st_data_index; // Stepper buffer common data index. Uses this information to execute this segment.
uint8_t flag; // Stepper algorithm bit-flag for special execution conditions.
} st_segment_t;
static st_segment_t segment_buffer[SEGMENT_BUFFER_SIZE];
// Step segment ring buffer indices
static volatile uint8_t segment_buffer_tail;
static volatile uint8_t segment_buffer_head;
static uint8_t segment_next_head;
static volatile uint8_t busy; // Used to avoid ISR nesting of the "Stepper Driver Interrupt". Should never occur though.
static plan_block_t *pl_current_block; // A pointer to the planner block currently being traced
static st_segment_t *st_current_segment;
static st_data_t *st_current_data;
// Pointers for the step segment being prepped from the planner buffer. Accessed only by the
// main program. Pointers may be planning segments or planner blocks ahead of what being executed.
static plan_block_t *pl_prep_block; // Pointer to the planner block being prepped
static st_data_t *st_prep_data; // Pointer to the stepper common data being prepped
static uint8_t pl_prep_index; // Index of planner block being prepped
static uint8_t st_data_prep_index; // Index of stepper common data block being prepped
static uint8_t pl_partial_block_flag; // Flag indicating the planner has modified the prepped planner block
/* __________________________
/| |\ _________________ ^
/ | | \ /| |\ |
/ | | \ / | | \ s
/ | | | | | \ p
/ | | | | | \ e
+-----+------------------------+---+--+---------------+----+ e
| BLOCK 1 | BLOCK 2 | d
time ----->
The trapezoid is the shape the speed curve over time. It starts at block->initial_rate, accelerates by block->rate_delta
until reaching cruising speed block->nominal_rate, and/or until step_events_remaining reaches block->decelerate_after
after which it decelerates until the block is completed. The driver uses constant acceleration, which is applied as
+/- block->rate_delta velocity increments by the midpoint rule at each ACCELERATION_TICKS_PER_SECOND.
*/
// Stepper state initialization. Cycle should only start if the st.cycle_start flag is
// enabled. Startup init and limits call this function but shouldn't start the cycle.
void st_wake_up()
{
// Enable steppers by resetting the stepper disable port
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
}
if (sys.state == STATE_CYCLE) {
// Initialize stepper output bits
st.out_bits = settings.invert_mask;
// Initialize step pulse timing from settings.
st.step_pulse_time = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND) >> 3);
// Enable stepper driver interrupt
st.execute_step = false;
st.load_flag = LOAD_BLOCK;
TCNT2 = 0; // Clear Timer2
TIMSK2 |= (1<<OCIE2A); // Enable Timer2 Compare Match A interrupt
TCCR2B = (1<<CS21); // Begin Timer2. Full speed, 1/8 prescaler
}
}
// Stepper shutdown
void st_go_idle()
{
// Disable stepper driver interrupt. Allow Timer0 to finish. It will disable itself.
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt
TCCR2B = 0; // Disable Timer2
busy = false;
// Disable steppers only upon system alarm activated or by user setting to not be kept enabled.
if ((settings.stepper_idle_lock_time != 0xff) || bit_istrue(sys.execute,EXEC_ALARM)) {
// Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
// stop and not drift from residual inertial forces at the end of the last movement.
delay_ms(settings.stepper_idle_lock_time);
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
}
}
}
/* "The Stepper Driver Interrupt" - This timer interrupt is the workhorse of Grbl. It is based
on an inverse time stepper algorithm, where a timer ticks at a constant frequency and uses
time-distance counters to track when its the approximate time for a step event. For reference,
a similar inverse-time algorithm by Pramod Ranade is susceptible to numerical round-off,
meaning that some axes steps may not execute correctly for a given multi-axis motion.
Grbl's algorithm differs by using a single inverse time-distance counter to manage a
Bresenham line algorithm for multi-axis step events, which ensures the number of steps for
each axis are executed exactly. In other words, Grbl uses a Bresenham within a Bresenham
algorithm, where one tracks time for step events and the other steps for multi-axis moves.
Grbl specifically uses the Bresenham algorithm due to its innate mathematical exactness and
low computational overhead, requiring simple integer +,- counters only.
This interrupt pops blocks from the step segment buffer and executes them by pulsing the
stepper pins appropriately. It is supported by The Stepper Port Reset Interrupt which it uses
to reset the stepper port after each pulse. The bresenham line tracer algorithm controls all
three stepper outputs simultaneously with these two interrupts.
*/
/* TODO:
- Measure time in ISR. Typical and worst-case. Should be virtually identical to last algorithm.
There are no major changes to the base operations of this ISR with the new segment buffer.
- Write how the acceleration counters work and why they are set at half via mid-point rule.
- Determine if placing the position counters elsewhere (or change them to 8-bit variables that
are added to the system position counters at the end of a segment) frees up cycles.
- Write a blurb about how the acceleration should be handled within the ISR. All of the
time/step/ramp counters accurately keep track of the remainders and phasing of the variables
with time. This means we do not have to compute them via expensive floating point beforehand.
- Need to do an analysis to determine if these counters are really that much cheaper. At least
find out when it isn't anymore. Particularly when the ISR is at a very high frequency.
*/
ISR(TIMER2_COMPA_vect)
{
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
if (busy) { return; } // The busy-flag is used to avoid reentering this interrupt
// Pulse stepper port pins, if flagged. New block dir will always be set one timer tick
// before any step pulse due to algorithm design.
if (st.execute_step) {
st.execute_step = false;
STEPPING_PORT = ( STEPPING_PORT & ~(DIRECTION_MASK | STEP_MASK) ) | st.out_bits;
TCNT0 = st.step_pulse_time; // Reload Timer0 counter.
TCCR0B = (1<<CS21); // Begin Timer0. Full speed, 1/8 prescaler
}
busy = true;
sei(); // Re-enable interrupts to allow Stepper Port Reset Interrupt to fire on-time.
// NOTE: The remaining code in this ISR will finish before returning to main program.
// If there is no step segment, attempt to pop one from the stepper buffer
if (st.load_flag != LOAD_NOOP) {
// Anything in the buffer? If so, load and initialize next step segment.
if (segment_buffer_head != segment_buffer_tail) {
// NOTE: Loads after a step event. At high rates above 1/2 ISR frequency, there is
// a small chance that this will load at the same time as a step event. Hopefully,
// the overhead for this loading event isn't too much.. possibly 2-5 usec.
// NOTE: The stepper algorithm must control the planner buffer tail as it completes
// the block moves. Otherwise, a feed hold can leave a few step buffer line moves
// without the correct planner block information.
st_current_segment = &segment_buffer[segment_buffer_tail];
// Load number of steps to execute from stepper buffer
st.segment_steps_remaining = st_current_segment->n_step;
// Check if the counters need to be reset for a new planner block
if (st.load_flag == LOAD_BLOCK) {
pl_current_block = plan_get_current_block(); // Should always be there. Stepper buffer handles this.
st_current_data = &segment_data[segment_buffer[segment_buffer_tail].st_data_index]; //st_current_segment->st_data_index];
// Initialize direction bits for block
st.out_bits = pl_current_block->direction_bits ^ settings.invert_mask;
st.execute_step = true; // Set flag to set direction bits upon next ISR tick.
// Initialize Bresenham line counters
st.counter_x = (pl_current_block->step_event_count >> 1);
st.counter_y = st.counter_x;
st.counter_z = st.counter_x;
// Initialize inverse time and step rate counter data
st.counter_d = st_current_data->d_next; // d_next always greater than delta_d.
if (st.delta_d < MINIMUM_STEP_RATE) { st.d_per_tick = MINIMUM_STEP_RATE; }
else { st.d_per_tick = st.delta_d; }
// During feed hold, do not update rate, ramp type, or ramp counters. Keep decelerating.
// if (sys.state == STATE_CYCLE) {
st.delta_d = st_current_data->initial_rate;
st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK/2; // Initialize ramp counter via midpoint rule
st.ramp_type = RAMP_NOOP_CRUISE; // Initialize as no ramp operation. Corrected later if necessary.
// }
}
// Acceleration and cruise handled by ramping. Just check if deceleration needs to begin.
if ( st_current_segment->flag & (SEGMENT_DECEL | SEGMENT_ACCEL) ) {
/* Compute correct ramp count for a ramp change. Upon a switch from acceleration to deceleration,
or vice-versa, the new ramp count must be set to trigger the next acceleration tick equal to
the number of ramp ISR ticks counted since the last acceleration tick. This is ensures the
ramp is executed exactly as the plan dictates. Otherwise, when a ramp begins from a known
rate (nominal/cruise or initial), the ramp count must be set to ISR_TICKS_PER_ACCELERATION_TICK/2
as mandated by the mid-point rule. For these conditions, the ramp count have been initialized
such that the following computation is still correct. */
st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK-st.ramp_count;
if ( st_current_segment->flag & SEGMENT_DECEL ) { st.ramp_type = RAMP_DECEL; }
else { st.ramp_type = RAMP_ACCEL; }
}
st.load_flag = LOAD_NOOP; // Segment motion loaded. Set no-operation flag to skip during execution.
} else {
// Can't discard planner block here if a feed hold stops in middle of block.
st_go_idle();
bit_true(sys.execute,EXEC_CYCLE_STOP); // Flag main program for cycle end
return; // Nothing to do but exit.
}
}
// Adjust inverse time counter for ac/de-celerations
// NOTE: Accelerations are handled by the stepper algorithm as it's thought to be more computationally
// efficient on the Arduino AVR. This could may not be true with higher ISR frequencies or faster CPUs.
if (st.ramp_type) { // Ignored when ramp type is NOOP_CRUISE
st.ramp_count--; // Tick acceleration ramp counter
if (st.ramp_count == 0) { // Adjust step rate when its time
if (st.ramp_type == RAMP_ACCEL) { // Adjust velocity for acceleration
st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK; // Reload ramp counter
st.delta_d += st_current_data->rate_delta;
if (st.delta_d >= st_current_data->nominal_rate) { // Reached nominal rate.
st.delta_d = st_current_data->nominal_rate; // Set cruising velocity
st.ramp_type = RAMP_NOOP_CRUISE; // Set ramp flag to cruising
st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK/2; // Re-initialize counter for next ramp.
}
} else { // Adjust velocity for deceleration.
st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK; // Reload ramp counter
if (st.delta_d > st_current_data->rate_delta) {
st.delta_d -= st_current_data->rate_delta;
} else { // Moving near zero feed rate. Gracefully slow down.
st.delta_d >>= 1; // Integer divide by 2 until complete. Also prevents overflow.
// TODO: Check for and handle feed hold exit? At this point, machine is stopped.
// - Set system flag to recompute plan and reset segment buffer.
// - Segment steps in buffer needs to be returned to planner correctly.
// busy = false;
// return;
}
}
// Finalize adjusted step rate. Ensure minimum.
if (st.delta_d < MINIMUM_STEP_RATE) { st.d_per_tick = MINIMUM_STEP_RATE; }
else { st.d_per_tick = st.delta_d; }
}
}
// Iterate inverse time counter. Triggers each Bresenham step event.
st.counter_d -= st.d_per_tick;
// Execute Bresenham step event, when it's time to do so.
if (st.counter_d < 0) {
st.counter_d += st_current_data->d_next; // Reload inverse time counter
st.out_bits = pl_current_block->direction_bits; // Reset out_bits and reload direction bits
st.execute_step = true;
// Execute step displacement profile by Bresenham line algorithm
st.counter_x -= pl_current_block->steps[X_AXIS];
if (st.counter_x < 0) {
st.out_bits |= (1<<X_STEP_BIT);
st.counter_x += pl_current_block->step_event_count;
// st.steps_x++;
if (st.out_bits & (1<<X_DIRECTION_BIT)) { sys.position[X_AXIS]--; }
else { sys.position[X_AXIS]++; }
}
st.counter_y -= pl_current_block->steps[Y_AXIS];
if (st.counter_y < 0) {
st.out_bits |= (1<<Y_STEP_BIT);
st.counter_y += pl_current_block->step_event_count;
// st.steps_y++;
if (st.out_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS]--; }
else { sys.position[Y_AXIS]++; }
}
st.counter_z -= pl_current_block->steps[Z_AXIS];
if (st.counter_z < 0) {
st.out_bits |= (1<<Z_STEP_BIT);
st.counter_z += pl_current_block->step_event_count;
// st.steps_z++;
if (st.out_bits & (1<<Z_DIRECTION_BIT)) { sys.position[Z_AXIS]--; }
else { sys.position[Z_AXIS]++; }
}
// Check step events for trapezoid change or end of block.
st.segment_steps_remaining--; // Decrement step events count
if (st.segment_steps_remaining == 0) {
/*
NOTE: sys.position updates could be done here. The bresenham counters can have
their own fast 8-bit addition-only counters. Here we would check the direction and
apply it to sys.position accordingly. However, this could take too much time
combined with loading a new segment during next cycle too.
TODO: Measure the time it would take in the worst case. It could still be faster
overall during segment execution if uint8 step counters tracked this and was added
to the system position variables here. Compared to worst case now, it wouldn't be
that much different.
// TODO: Upon loading, step counters would need to be zeroed.
// TODO: For feedrate overrides, we will have to execute add these values.. although
// for probing, this breaks. Current values won't be correct, unless we query it.
// It makes things more complicated, but still manageable.
if (st.steps_x > 0) {
if (st.out_bits & (1<<X_DIRECTION_BIT)) { sys.position[X_AXIS] += st.steps_x; }
else { sys.position[X_AXIS] -= st.steps_x; }
}
if (st.steps_y > 0) {
if (st.out_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS] += st.steps_y; }
else { sys.position[Y_AXIS] -= st.steps_y; }
}
if (st.steps_z > 0) {
if (st.out_bits & (1<<Z_DIRECTION_BIT)) { sys.position[Z_AXIS] += st.steps_z; }
else { sys.position[Z_AXIS] -= st.steps_z; }
}
*/
// Line move is complete, set load line flag to check for new move.
// Check if last line move in planner block. Discard if so.
if (st_current_segment->flag & SEGMENT_END_OF_BLOCK) {
plan_discard_current_block();
st.load_flag = LOAD_BLOCK;
} else {
st.load_flag = LOAD_SEGMENT;
}
// Discard current segment by advancing buffer tail index
if ( ++segment_buffer_tail == SEGMENT_BUFFER_SIZE) { segment_buffer_tail = 0; }
}
st.out_bits ^= settings.invert_mask; // Apply step port invert mask
}
busy = false;
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
}
// The Stepper Port Reset Interrupt: Timer0 OVF interrupt handles the falling edge of the step
// pulse. This should always trigger before the next Timer2 COMPA interrupt and independently
// finish, if Timer2 is disabled after completing a move.
ISR(TIMER0_OVF_vect)
{
STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | (settings.invert_mask & STEP_MASK);
TCCR0B = 0; // Disable timer until needed.
}
// Reset and clear stepper subsystem variables
void st_reset()
{
memset(&st, 0, sizeof(st));
st.load_flag = LOAD_BLOCK;
busy = false;
pl_current_block = NULL; // Planner block pointer used by stepper algorithm
pl_prep_block = NULL; // Planner block pointer used by segment buffer
pl_prep_index = 0; // Planner buffer indices are also reset to zero.
st_data_prep_index = 0;
segment_buffer_tail = 0;
segment_buffer_head = 0; // empty = tail
segment_next_head = 1;
pl_partial_block_flag = false;
}
// Initialize and start the stepper motor subsystem
void st_init()
{
// Configure directions of interface pins
STEPPING_DDR |= STEPPING_MASK;
STEPPING_PORT = (STEPPING_PORT & ~STEPPING_MASK) | settings.invert_mask;
STEPPERS_DISABLE_DDR |= 1<<STEPPERS_DISABLE_BIT;
// Configure Timer 2
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt while configuring it
TCCR2B = 0; // Disable Timer2 until needed
TCNT2 = 0; // Clear Timer2 counter
TCCR2A = (1<<WGM21); // Set CTC mode
OCR2A = (F_CPU/ISR_TICKS_PER_SECOND)/8 - 1; // Set Timer2 CTC rate
// Configure Timer 0
TIMSK0 &= ~(1<<TOIE0);
TCCR0A = 0; // Normal operation
TCCR0B = 0; // Disable Timer0 until needed
TIMSK0 |= (1<<TOIE0); // Enable overflow interrupt
// Start in the idle state, but first wake up to check for keep steppers enabled option.
st_wake_up();
st_go_idle();
}
// Planner external interface to start stepper interrupt and execute the blocks in queue. Called
// by the main program functions: planner auto-start and run-time command execution.
void st_cycle_start()
{
if (sys.state == STATE_QUEUED) {
sys.state = STATE_CYCLE;
st_wake_up();
}
}
// Execute a feed hold with deceleration, only during cycle. Called by main program.
void st_feed_hold()
{
if (sys.state == STATE_CYCLE) {
sys.state = STATE_HOLD;
sys.auto_start = false; // Disable planner auto start upon feed hold.
}
}
// Reinitializes the cycle plan and stepper system after a feed hold for a resume. Called by
// runtime command execution in the main program, ensuring that the planner re-plans safely.
// NOTE: Bresenham algorithm variables are still maintained through both the planner and stepper
// cycle reinitializations. The stepper path should continue exactly as if nothing has happened.
// Only the planner de/ac-celerations profiles and stepper rates have been updated.
void st_cycle_reinitialize()
{
// if (pl_current_block != NULL) {
// Replan buffer from the feed hold stop location.
// TODO: Need to add up all of the step events in the current planner block to give
// back to the planner. Should only need it for the current block.
// BUT! The planner block millimeters is all changed and may be changed into the next
// planner block. The block millimeters would need to be recalculated via step counts
// and the mm/step variable.
// OR. Do we plan the feed hold itself down with the planner.
// plan_cycle_reinitialize(st_current_data->step_events_remaining);
// st.ramp_type = RAMP_ACCEL;
// st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK/2;
// st.delta_d = 0;
// sys.state = STATE_QUEUED;
// } else {
// sys.state = STATE_IDLE;
// }
sys.state = STATE_IDLE;
}
/* Prepares step segment buffer. Continuously called from main program.
The segment buffer is an intermediary buffer interface between the execution of steps
by the stepper algorithm and the velocity profiles generated by the planner. The stepper
algorithm only executes steps within the segment buffer and is filled by the main program
when steps are "checked-out" from the first block in the planner buffer. This keeps the
step execution and planning optimization processes atomic and protected from each other.
The number of steps "checked-out" from the planner buffer and the number of segments in
the segment buffer is sized and computed such that no operation in the main program takes
longer than the time it takes the stepper algorithm to empty it before refilling it.
Currently, the segment buffer conservatively holds roughly up to 40-60 msec of steps.
NOTE: The segment buffer executes a set number of steps over an approximate time period.
If we try to execute over a set time period, it is difficult to guarantee or predict how
many steps will execute over it, especially when the step pulse phasing between the
neighboring segments are kept consistent. Meaning that, if the last segment step pulses
right before its end, the next segment must delay its first pulse so that the step pulses
are consistently spaced apart over time to keep the step pulse train nice and smooth.
Keeping track of phasing and ensuring that the exact number of steps are executed as
defined by the planner block, the related computational overhead gets quickly and
prohibitively expensive, especially in real-time.
Since the stepper algorithm automatically takes care of the step pulse phasing with
its ramp and inverse time counters, we don't have to explicitly and expensively track the
exact number of steps, time, or phasing of steps. All we need to do is approximate
the number of steps in each segment such that the segment buffer has enough execution time
for the main program to do what it needs to do and refill it when it has time. In other
words, we just need to compute a cheap approximation of the current velocity and the
number of steps over it.
*/
/*
TODO: Figure out how to enforce a deceleration when a feedrate override is reduced.
The problem is that when an override is reduced, the planner may not plan back to
the current rate. Meaning that the velocity profiles for certain conditions no longer
are trapezoidal or triangular. For example, if the current block is cruising at a
nominal rate and the feedrate override is reduced, the new nominal rate will now be
lower. The velocity profile must first decelerate to the new nominal rate and then
follow on the new plan. So the remaining velocity profile will have a decelerate,
cruise, and another decelerate.
Another issue is whether or not a feedrate override reduction causes a deceleration
that acts over several planner blocks. For example, say that the plan is already
heavily decelerating throughout it, reducing the feedrate will not do much to it. So,
how do we determine when to resume the new plan? How many blocks do we have to wait
until the new plan intersects with the deceleration curve? One plus though, the
deceleration will never be more than the number of blocks in the entire planner buffer,
but it theoretically can be equal to it when all planner blocks are decelerating already.
*/
void st_prep_buffer()
{
while (segment_buffer_tail != segment_next_head) { // Check if we need to fill the buffer.
// Initialize new segment
st_segment_t *prep_segment = &segment_buffer[segment_buffer_head];
prep_segment->flag = SEGMENT_NOOP;
// Determine if we need to load a new planner block.
if (pl_prep_block == NULL) {
pl_prep_block = plan_get_block_by_index(pl_prep_index); // Query planner for a queued block
if (pl_prep_block == NULL) { return; } // No planner blocks. Exit.
// Increment stepper common data index
if ( ++st_data_prep_index == (SEGMENT_BUFFER_SIZE-1) ) { st_data_prep_index = 0; }
// Check if the planner has re-computed this block mid-execution. If so, push the previous segment
// data. Otherwise, prepare a new segment data for the new planner block.
if (pl_partial_block_flag) {
// Prepare new shared segment block data and copy the relevant last segment block data.
st_data_t *last_st_prep_data;
last_st_prep_data = st_prep_data;
st_prep_data = &segment_data[st_data_prep_index];
st_prep_data->step_events_remaining = last_st_prep_data->step_events_remaining;
st_prep_data->rate_delta = last_st_prep_data->rate_delta;
st_prep_data->d_next = last_st_prep_data->d_next;
st_prep_data->nominal_rate = last_st_prep_data->nominal_rate; // TODO: Feedrate overrides recomputes this.
st_prep_data->mm_per_step = last_st_prep_data->mm_per_step;
pl_partial_block_flag = false; // Reset flag
} else {
// Prepare commonly shared planner block data for the ensuing segment buffer moves ad-hoc, since
// the planner buffer can dynamically change the velocity profile data as blocks are added.
st_prep_data = &segment_data[st_data_prep_index];
// Initialize Bresenham variables
st_prep_data->step_events_remaining = pl_prep_block->step_event_count;
// Convert planner block velocity profile data to stepper rate and step distance data.
st_prep_data->nominal_rate = ceil(sqrt(pl_prep_block->nominal_speed_sqr)*(INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
st_prep_data->rate_delta = ceil(pl_prep_block->acceleration*
((INV_TIME_MULTIPLIER/(60.0*60.0))/(ISR_TICKS_PER_SECOND*ACCELERATION_TICKS_PER_SECOND))); // (mult*mm/isr_tic/accel_tic)
st_prep_data->d_next = ceil((pl_prep_block->millimeters*INV_TIME_MULTIPLIER)/pl_prep_block->step_event_count); // (mult*mm/step)
// TODO: Check if we really need to store this.
st_prep_data->mm_per_step = pl_prep_block->millimeters/pl_prep_block->step_event_count;
}
// Convert planner entry speed to stepper initial rate.
st_prep_data->initial_rate = ceil(sqrt(pl_prep_block->entry_speed_sqr)*(INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
// TODO: Nominal rate changes with feedrate override.
// st_prep_data->nominal_rate = ceil(sqrt(pl_prep_block->nominal_speed_sqr)*(INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
st_prep_data->current_approx_rate = st_prep_data->initial_rate;
// Calculate the planner block velocity profile type, determine deceleration point, and initial ramp.
float mm_decelerate_after = plan_calculate_velocity_profile(pl_prep_index);
st_prep_data->decelerate_after = ceil( mm_decelerate_after/st_prep_data->mm_per_step );
if (st_prep_data->decelerate_after > 0) { // If 0, SEGMENT_DECEL flag is set later.
if (st_prep_data->initial_rate != st_prep_data->nominal_rate) { prep_segment->flag = SEGMENT_ACCEL; }
}
}
// Set new segment to point to the current segment data block.
prep_segment->st_data_index = st_data_prep_index;
// Approximate the velocity over the new segment using the already computed rate values.
// NOTE: This assumes that each segment will have an execution time roughly equal to every ACCELERATION_TICK.
// We do this to minimize memory and computational requirements. However, this could easily be replaced with
// a more exact approximation or have a unique time per segment, if CPU and memory overhead allows.
if (st_prep_data->decelerate_after <= 0) {
if (st_prep_data->decelerate_after == 0) { prep_segment->flag = SEGMENT_DECEL; } // Set segment deceleration flag
else { st_prep_data->current_approx_rate -= st_prep_data->rate_delta; }
if (st_prep_data->current_approx_rate < st_prep_data->rate_delta) { st_prep_data->current_approx_rate >>= 1; }
} else {
if (st_prep_data->current_approx_rate < st_prep_data->nominal_rate) {
st_prep_data->current_approx_rate += st_prep_data->rate_delta;
if (st_prep_data->current_approx_rate > st_prep_data->nominal_rate) {
st_prep_data->current_approx_rate = st_prep_data->nominal_rate;
}
}
}
// Compute the number of steps in the prepped segment based on the approximate current rate.
// NOTE: The d_next divide cancels out the INV_TIME_MULTIPLIER and converts the rate value to steps.
prep_segment->n_step = ceil(max(MINIMUM_STEP_RATE,st_prep_data->current_approx_rate)*
(ISR_TICKS_PER_SECOND/ACCELERATION_TICKS_PER_SECOND)/st_prep_data->d_next);
// NOTE: Ensures it moves for very slow motions, but MINIMUM_STEP_RATE should always set this too. Perhaps
// a compile-time check to see if MINIMUM_STEP_RATE is set high enough is all that is needed.
prep_segment->n_step = max(prep_segment->n_step,MINIMUM_STEPS_PER_SEGMENT);
// NOTE: As long as the ACCELERATION_TICKS_PER_SECOND is valid, n_step should never exceed 255 and overflow.
// prep_segment->n_step = min(prep_segment->n_step,MAXIMUM_STEPS_PER_BLOCK); // Prevent unsigned int8 overflow.
// Check if n_step exceeds steps remaining in planner block. If so, truncate.
if (prep_segment->n_step > st_prep_data->step_events_remaining) {
prep_segment->n_step = st_prep_data->step_events_remaining;
}
// Check if n_step crosses decelerate point in block. If so, truncate to ensure the deceleration
// ramp counters are set correctly during execution.
if (st_prep_data->decelerate_after > 0) {
if (prep_segment->n_step > st_prep_data->decelerate_after) {
prep_segment->n_step = st_prep_data->decelerate_after;
}
}
// Update stepper common data variables.
st_prep_data->decelerate_after -= prep_segment->n_step;
st_prep_data->step_events_remaining -= prep_segment->n_step;
// Check for end of planner block
if ( st_prep_data->step_events_remaining == 0 ) {
// Set EOB bitflag so stepper algorithm discards the planner block after this segment completes.
prep_segment->flag |= SEGMENT_END_OF_BLOCK;
// Move planner pointer to next block and flag to load a new block for the next segment.
pl_prep_index = plan_next_block_index(pl_prep_index);
pl_prep_block = NULL;
}
// New step segment completed. Increment segment buffer indices.
segment_buffer_head = segment_next_head;
if ( ++segment_next_head == SEGMENT_BUFFER_SIZE ) { segment_next_head = 0; }
// long a = prep_segment->n_step;
// printInteger(a);
// printString(" ");
}
}
uint8_t st_get_prep_block_index()
{
// Returns only the index but doesn't state if the block has been partially executed. How do we simply check for this?
return(pl_prep_index);
}
void st_fetch_partial_block_parameters(uint8_t block_index, float *millimeters_remaining, uint8_t *is_decelerating)
{
// if called, can we assume that this always changes and needs to be updated? if so, then
// we can perform all of the segment buffer setup tasks here to make sure the next time
// the segments are loaded, the st_data buffer is updated correctly.
// !!! Make sure that this is always pointing to the correct st_prep_data block.
// When a mid-block acceleration occurs, we have to make sure the ramp counters are updated
// correctly, much in the same fashion as the deceleration counters. Need to think about this
// make sure this is right, but i'm pretty sure it is.
// TODO: NULL means that the segment buffer has just completed a planner block. Clean up!
if (pl_prep_block != NULL) {
*millimeters_remaining = st_prep_data->step_events_remaining*st_prep_data->mm_per_step;
if (st_prep_data->decelerate_after > 0) { *is_decelerating = false; }
else { *is_decelerating = true; }
// Flag for new prep_block when st_prep_buffer() is called after the planner recomputes.
pl_partial_block_flag = true;
pl_prep_block = NULL;
}
return;
}

775
archive/stepper_time.c
View File

@ -1,775 +0,0 @@
/*
stepper.c - stepper motor driver: executes motion plans using stepper motors
Part of Grbl
Copyright (c) 2011-2013 Sungeun K. Jeon
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/>.
*/
#include <avr/interrupt.h>
#include "stepper.h"
#include "config.h"
#include "settings.h"
#include "planner.h"
#include "nuts_bolts.h"
// Some useful constants
#define TICKS_PER_MICROSECOND (F_CPU/1000000)
#define RAMP_NOOP_CRUISE 0
#define RAMP_ACCEL 1
#define RAMP_DECEL 2
#define LOAD_NOOP 0
#define LOAD_SEGMENT 1
#define LOAD_BLOCK 2
#define SEGMENT_NOOP 0
#define SEGMENT_END_OF_BLOCK bit(0)
#define RAMP_CHANGE_ACCEL bit(1)
#define RAMP_CHANGE_DECEL bit(2)
#define MINIMUM_STEPS_PER_SEGMENT 1 // Don't change
#define SEGMENT_BUFFER_SIZE 6
#define DT_SEGMENT ACCELERATION_TICKS_PER_SECOND/ISR_TICKS_PER_SECOND
// Stepper state variable. Contains running data and trapezoid variables.
typedef struct {
// Used by the bresenham line algorithm
int32_t counter_x, // Counter variables for the bresenham line tracer
counter_y,
counter_z;
// Used by inverse time algorithm to track step rate
int32_t counter_dist; // Inverse time distance traveled since last step event
uint8_t step_count; // Steps remaining in line segment motion
uint8_t phase_count; // Phase ticks remaining after line segment steps complete
// Used by the stepper driver interrupt
uint8_t execute_step; // Flags step execution for each interrupt.
uint8_t step_pulse_time; // Step pulse reset time after step rise
uint8_t out_bits; // The next stepping-bits to be output
uint8_t load_flag;
} stepper_t;
static stepper_t st;
// Stores stepper common data for executing steps in the segment buffer. Data can change mid-block when the
// planner updates the remaining block velocity profile with a more optimal plan or a feedrate override occurs.
// NOTE: Normally, this buffer is partially in-use, but, for the worst case scenario, it will never exceed
// the number of accessible stepper buffer segments (SEGMENT_BUFFER_SIZE-1).
typedef struct {
uint32_t dist_per_step;
float step_events_remaining; // Tracks step event count for the executing planner block
float accelerate_until;
float decelerate_after;
float current_rate;
float maximum_rate;
float exit_rate;
float acceleration;
float step_per_mm;
} st_data_t;
static st_data_t segment_data[SEGMENT_BUFFER_SIZE-1];
// Primary stepper segment ring buffer. Contains small, short line segments for the stepper algorithm to execute,
// which are "checked-out" incrementally from the first block in the planner buffer. Once "checked-out", the steps
// in the segments buffer cannot be modified by the planner, where the remaining planner block steps still can.
typedef struct {
uint8_t n_step; // Number of step events to be executed for this segment
uint8_t n_phase_tick;
uint32_t dist_per_tick;
uint8_t st_data_index; // Stepper buffer common data index. Uses this information to execute this segment.
uint8_t flag; // Stepper algorithm bit-flag for special execution conditions.
} st_segment_t;
static st_segment_t segment_buffer[SEGMENT_BUFFER_SIZE];
// Step segment ring buffer indices
static volatile uint8_t segment_buffer_tail;
static volatile uint8_t segment_buffer_head;
static uint8_t segment_next_head;
static volatile uint8_t busy; // Used to avoid ISR nesting of the "Stepper Driver Interrupt". Should never occur though.
static plan_block_t *pl_current_block; // A pointer to the planner block currently being traced
static st_segment_t *st_current_segment;
static st_data_t *st_current_data;
// Pointers for the step segment being prepped from the planner buffer. Accessed only by the
// main program. Pointers may be planning segments or planner blocks ahead of what being executed.
static plan_block_t *pl_prep_block; // Pointer to the planner block being prepped
static st_data_t *st_prep_data; // Pointer to the stepper common data being prepped
static uint8_t pl_prep_index; // Index of planner block being prepped
static uint8_t st_data_prep_index; // Index of stepper common data block being prepped
static uint8_t pl_partial_block_flag; // Flag indicating the planner has modified the prepped planner block
/* __________________________
/| |\ _________________ ^
/ | | \ /| |\ |
/ | | \ / | | \ s
/ | | | | | \ p
/ | | | | | \ e
+-----+------------------------+---+--+---------------+----+ e
| BLOCK 1 | BLOCK 2 | d
time ----->
The trapezoid is the shape the speed curve over time. It starts at block->initial_rate, accelerates by block->rate_delta
until reaching cruising speed block->nominal_rate, and/or until step_events_remaining reaches block->decelerate_after
after which it decelerates until the block is completed. The driver uses constant acceleration, which is applied as
+/- block->rate_delta velocity increments by the midpoint rule at each ACCELERATION_TICKS_PER_SECOND.
*/
// Stepper state initialization. Cycle should only start if the st.cycle_start flag is
// enabled. Startup init and limits call this function but shouldn't start the cycle.
void st_wake_up()
{
// Enable steppers by resetting the stepper disable port
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
}
if (sys.state == STATE_CYCLE) {
// Initialize stepper output bits
st.out_bits = settings.invert_mask;
// Initialize step pulse timing from settings.
st.step_pulse_time = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND) >> 3);
// Enable stepper driver interrupt
st.execute_step = false;
st.load_flag = LOAD_BLOCK;
TCNT2 = 0; // Clear Timer2
TIMSK2 |= (1<<OCIE2A); // Enable Timer2 Compare Match A interrupt
TCCR2B = (1<<CS21); // Begin Timer2. Full speed, 1/8 prescaler
}
}
// Stepper shutdown
void st_go_idle()
{
// Disable stepper driver interrupt. Allow Timer0 to finish. It will disable itself.
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt
TCCR2B = 0; // Disable Timer2
busy = false;
// Disable steppers only upon system alarm activated or by user setting to not be kept enabled.
if ((settings.stepper_idle_lock_time != 0xff) || bit_istrue(sys.execute,EXEC_ALARM)) {
// Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
// stop and not drift from residual inertial forces at the end of the last movement.
delay_ms(settings.stepper_idle_lock_time);
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
}
}
}
/* "The Stepper Driver Interrupt" - This timer interrupt is the workhorse of Grbl. It is based
on an inverse time stepper algorithm, where a timer ticks at a constant frequency and uses
time-distance counters to track when its the approximate time for a step event. For reference,
a similar inverse-time algorithm by Pramod Ranade is susceptible to numerical round-off, as
described, meaning that some axes steps may not execute correctly for a given multi-axis motion.
Grbl's algorithm differs by using a single inverse time-distance counter to manage a
Bresenham line algorithm for multi-axis step events, which ensures the number of steps for
each axis are executed exactly. In other words, Grbl uses a Bresenham within a Bresenham
algorithm, where one tracks time for step events and the other steps for multi-axis moves.
Grbl specifically uses the Bresenham algorithm due to its innate mathematical exactness and
low computational overhead, requiring simple integer +,- counters only.
This interrupt pops blocks from the step segment buffer and executes them by pulsing the
stepper pins appropriately. It is supported by The Stepper Port Reset Interrupt which it uses
to reset the stepper port after each pulse. The bresenham line tracer algorithm controls all
three stepper outputs simultaneously with these two interrupts.
*/
/* TODO:
- Measure time in ISR. Typical and worst-case. Should be virtually identical to last algorithm.
There are no major changes to the base operations of this ISR with the new segment buffer.
- Write how the acceleration counters work and why they are set at half via mid-point rule.
- Determine if placing the position counters elsewhere (or change them to 8-bit variables that
are added to the system position counters at the end of a segment) frees up cycles.
- Write a blurb about how the acceleration should be handled within the ISR. All of the
time/step/ramp counters accurately keep track of the remainders and phasing of the variables
with time. This means we do not have to compute them via expensive floating point beforehand.
- Need to do an analysis to determine if these counters are really that much cheaper. At least
find out when it isn't anymore. Particularly when the ISR is at a very high frequency.
- Create NOTE: to describe that the total time in this ISR must be less than the ISR frequency
in its worst case scenario.
*/
ISR(TIMER2_COMPA_vect)
{
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
if (busy) { return; } // The busy-flag is used to avoid reentering this interrupt
// Pulse stepper port pins, if flagged. New block dir will always be set one timer tick
// before any step pulse due to algorithm design.
if (st.execute_step) {
st.execute_step = false;
STEPPING_PORT = ( STEPPING_PORT & ~(DIRECTION_MASK | STEP_MASK) ) | st.out_bits;
TCNT0 = st.step_pulse_time; // Reload Timer0 counter.
TCCR0B = (1<<CS21); // Begin Timer0. Full speed, 1/8 prescaler
}
busy = true;
sei(); // Re-enable interrupts to allow Stepper Port Reset Interrupt to fire on-time.
// NOTE: The remaining code in this ISR will finish before returning to main program.
// If there is no step segment, attempt to pop one from the stepper buffer
if (st.load_flag != LOAD_NOOP) {
// Anything in the buffer? If so, load and initialize next step segment.
if (segment_buffer_head != segment_buffer_tail) {
// Initialize new step segment and load number of steps to execute
st_current_segment = &segment_buffer[segment_buffer_tail];
st.step_count = st_current_segment->n_step;
// If the new segment starts a new planner block, initialize stepper variables and counters.
// NOTE: For new segments only, the step counters are not updated to ensure step phasing is continuous.
if (st.load_flag == LOAD_BLOCK) {
pl_current_block = plan_get_current_block(); // Should always be there. Stepper buffer handles this.
st_current_data = &segment_data[segment_buffer[segment_buffer_tail].st_data_index];
// Initialize direction bits for block. Set execute flag to set directions bits upon next ISR tick.
st.out_bits = pl_current_block->direction_bits ^ settings.invert_mask;
st.execute_step = true;
// Initialize Bresenham line counters
st.counter_x = (pl_current_block->step_event_count >> 1);
st.counter_y = st.counter_x;
st.counter_z = st.counter_x;
// Initialize inverse time, step rate data, and acceleration ramp counters
st.counter_dist = st_current_data->dist_per_step; // dist_per_step always greater than dist_per_tick.
}
st.load_flag = LOAD_NOOP; // Segment motion loaded. Set no-operation flag to skip during execution.
} else {
// Can't discard planner block here if a feed hold stops in middle of block.
st_go_idle();
bit_true(sys.execute,EXEC_CYCLE_STOP); // Flag main program for cycle end
return; // Nothing to do but exit.
}
}
// Iterate inverse time counter. Triggers each Bresenham step event.
st.counter_dist -= st_current_segment->dist_per_tick;
// Execute Bresenham step event, when it's time to do so.
if (st.counter_dist < 0) {
if (st.step_count > 0) { // Block phase correction from executing step.
st.counter_dist += st_current_data->dist_per_step; // Reload inverse time counter
st.out_bits = pl_current_block->direction_bits; // Reset out_bits and reload direction bits
st.execute_step = true;
// Execute step displacement profile by Bresenham line algorithm
st.counter_x -= pl_current_block->steps[X_AXIS];
if (st.counter_x < 0) {
st.out_bits |= (1<<X_STEP_BIT);
st.counter_x += pl_current_block->step_event_count;
if (st.out_bits & (1<<X_DIRECTION_BIT)) { sys.position[X_AXIS]--; }
else { sys.position[X_AXIS]++; }
}
st.counter_y -= pl_current_block->steps[Y_AXIS];
if (st.counter_y < 0) {
st.out_bits |= (1<<Y_STEP_BIT);
st.counter_y += pl_current_block->step_event_count;
if (st.out_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS]--; }
else { sys.position[Y_AXIS]++; }
}
st.counter_z -= pl_current_block->steps[Z_AXIS];
if (st.counter_z < 0) {
st.out_bits |= (1<<Z_STEP_BIT);
st.counter_z += pl_current_block->step_event_count;
if (st.out_bits & (1<<Z_DIRECTION_BIT)) { sys.position[Z_AXIS]--; }
else { sys.position[Z_AXIS]++; }
}
// Check step events for trapezoid change or end of block.
st.step_count--; // Decrement step events count
st.out_bits ^= settings.invert_mask; // Apply step port invert mask
}
}
if (st.step_count == 0) {
if (st.phase_count == 0) {
// Line move is complete, set load line flag to check for new move.
// Check if last line move in planner block. Discard if so.
if (st_current_segment->flag & SEGMENT_END_OF_BLOCK) {
plan_discard_current_block();
st.load_flag = LOAD_BLOCK;
} else {
st.load_flag = LOAD_SEGMENT;
}
// Discard current segment by advancing buffer tail index
if ( ++segment_buffer_tail == SEGMENT_BUFFER_SIZE) { segment_buffer_tail = 0; }
}
st.phase_count--;
}
busy = false;
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
}
// The Stepper Port Reset Interrupt: Timer0 OVF interrupt handles the falling edge of the step
// pulse. This should always trigger before the next Timer2 COMPA interrupt and independently
// finish, if Timer2 is disabled after completing a move.
ISR(TIMER0_OVF_vect)
{
STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | (settings.invert_mask & STEP_MASK);
TCCR0B = 0; // Disable timer until needed.
}
// Reset and clear stepper subsystem variables
void st_reset()
{
memset(&st, 0, sizeof(st));
st.load_flag = LOAD_BLOCK;
busy = false;
pl_current_block = NULL; // Planner block pointer used by stepper algorithm
pl_prep_block = NULL; // Planner block pointer used by segment buffer
pl_prep_index = 0; // Planner buffer indices are also reset to zero.
st_data_prep_index = 0;
segment_buffer_tail = 0;
segment_buffer_head = 0; // empty = tail
segment_next_head = 1;
pl_partial_block_flag = false;
}
// Initialize and start the stepper motor subsystem
void st_init()
{
// Configure directions of interface pins
STEPPING_DDR |= STEPPING_MASK;
STEPPING_PORT = (STEPPING_PORT & ~STEPPING_MASK) | settings.invert_mask;
STEPPERS_DISABLE_DDR |= 1<<STEPPERS_DISABLE_BIT;
// Configure Timer 2
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt while configuring it
TCCR2B = 0; // Disable Timer2 until needed
TCNT2 = 0; // Clear Timer2 counter
TCCR2A = (1<<WGM21); // Set CTC mode
OCR2A = (F_CPU/ISR_TICKS_PER_SECOND)/8 - 1; // Set Timer2 CTC rate
// Configure Timer 0
TIMSK0 &= ~(1<<TOIE0);
TCCR0A = 0; // Normal operation
TCCR0B = 0; // Disable Timer0 until needed
TIMSK0 |= (1<<TOIE0); // Enable overflow interrupt
// Start in the idle state, but first wake up to check for keep steppers enabled option.
st_wake_up();
st_go_idle();
}
// Planner external interface to start stepper interrupt and execute the blocks in queue. Called
// by the main program functions: planner auto-start and run-time command execution.
void st_cycle_start()
{
if (sys.state == STATE_QUEUED) {
sys.state = STATE_CYCLE;
st_prep_buffer(); // Initialize step segment buffer before beginning cycle.
st_wake_up();
}
}
// Execute a feed hold with deceleration, only during cycle. Called by main program.
void st_feed_hold()
{
if (sys.state == STATE_CYCLE) {
sys.state = STATE_HOLD;
sys.auto_start = false; // Disable planner auto start upon feed hold.
}
}
// Reinitializes the cycle plan and stepper system after a feed hold for a resume. Called by
// runtime command execution in the main program, ensuring that the planner re-plans safely.
// NOTE: Bresenham algorithm variables are still maintained through both the planner and stepper
// cycle reinitializations. The stepper path should continue exactly as if nothing has happened.
// Only the planner de/ac-celerations profiles and stepper rates have been updated.
void st_cycle_reinitialize()
{
// if (pl_current_block != NULL) {
// Replan buffer from the feed hold stop location.
// TODO: Need to add up all of the step events in the current planner block to give
// back to the planner. Should only need it for the current block.
// BUT! The planner block millimeters is all changed and may be changed into the next
// planner block. The block millimeters would need to be recalculated via step counts
// and the mm/step variable.
// OR. Do we plan the feed hold itself down with the planner.
// plan_cycle_reinitialize(st_current_data->step_events_remaining);
// st.ramp_type = RAMP_ACCEL;
// st.counter_ramp = ISR_TICKS_PER_ACCELERATION_TICK/2;
// st.ramp_rate = 0;
// sys.state = STATE_QUEUED;
// } else {
// sys.state = STATE_IDLE;
// }
sys.state = STATE_IDLE;
}
/* Prepares step segment buffer. Continuously called from main program.
The segment buffer is an intermediary buffer interface between the execution of steps
by the stepper algorithm and the velocity profiles generated by the planner. The stepper
algorithm only executes steps within the segment buffer and is filled by the main program
when steps are "checked-out" from the first block in the planner buffer. This keeps the
step execution and planning optimization processes atomic and protected from each other.
The number of steps "checked-out" from the planner buffer and the number of segments in
the segment buffer is sized and computed such that no operation in the main program takes
longer than the time it takes the stepper algorithm to empty it before refilling it.
Currently, the segment buffer conservatively holds roughly up to 40-60 msec of steps.
NOTE: The segment buffer executes a set number of steps over an approximate time period.
If we try to execute over a fixed time period, it is difficult to guarantee or predict
how many steps will execute over it, especially when the step pulse phasing between the
neighboring segments must also be kept consistent. Meaning that, if the last segment step
pulses right before a segment end, the next segment must delay its first pulse so that the
step pulses are consistently spaced apart over time to keep the step pulse train nice and
smooth. Keeping track of phasing and ensuring that the exact number of steps are executed
as defined by the planner block, the related computational overhead can get quickly and
prohibitively expensive, especially in real-time.
Since the stepper algorithm automatically takes care of the step pulse phasing with
its ramp and inverse time counters by retaining the count remainders, we don't have to
explicitly and expensively track and synchronize the exact number of steps, time, and
phasing of steps. All we need to do is approximate the number of steps in each segment
such that the segment buffer has enough execution time for the main program to do what
it needs to do and refill it when it comes back. In other words, we just need to compute
a cheap approximation of the current velocity and the number of steps over it.
*/
/*
TODO: Figure out how to enforce a deceleration when a feedrate override is reduced.
The problem is that when an override is reduced, the planner may not plan back to
the current rate. Meaning that the velocity profiles for certain conditions no longer
are trapezoidal or triangular. For example, if the current block is cruising at a
nominal rate and the feedrate override is reduced, the new nominal rate will now be
lower. The velocity profile must first decelerate to the new nominal rate and then
follow on the new plan. So the remaining velocity profile will have a decelerate,
cruise, and another decelerate.
Another issue is whether or not a feedrate override reduction causes a deceleration
that acts over several planner blocks. For example, say that the plan is already
heavily decelerating throughout it, reducing the feedrate will not do much to it. So,
how do we determine when to resume the new plan? How many blocks do we have to wait
until the new plan intersects with the deceleration curve? One plus though, the
deceleration will never be more than the number of blocks in the entire planner buffer,
but it theoretically can be equal to it when all planner blocks are decelerating already.
*/
void st_prep_buffer()
{
if (sys.state == STATE_QUEUED) { return; } // Block until a motion state is issued
while (segment_buffer_tail != segment_next_head) { // Check if we need to fill the buffer.
// Initialize new segment
st_segment_t *prep_segment = &segment_buffer[segment_buffer_head];
prep_segment->flag = SEGMENT_NOOP;
// -----------------------------------------------------------------------------------
// Determine if we need to load a new planner block. If so, prepare step data.
if (pl_prep_block == NULL) {
pl_prep_block = plan_get_block_by_index(pl_prep_index); // Query planner for a queued block
if (pl_prep_block == NULL) { return; } // No planner blocks. Exit.
SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
// Increment stepper common data index
if ( ++st_data_prep_index == (SEGMENT_BUFFER_SIZE-1) ) { st_data_prep_index = 0; }
// Check if the planner has re-computed this block mid-execution. If so, push the previous
// segment data. Otherwise, prepare a new segment data for the new planner block.
if (pl_partial_block_flag) {
// Prepare new shared segment block data and copy the relevant last segment block data.
st_data_t *last_st_prep_data;
last_st_prep_data = st_prep_data;
st_prep_data = &segment_data[st_data_prep_index];
st_prep_data->step_events_remaining = last_st_prep_data->step_events_remaining;
st_prep_data->dist_per_step = last_st_prep_data->dist_per_step;
st_prep_data->step_per_mm = last_st_prep_data->step_per_mm;
st_prep_data->acceleration = last_st_prep_data->acceleration;
pl_partial_block_flag = false; // Reset flag
} else {
// Prepare commonly shared planner block data for the ensuing segment buffer moves ad-hoc, since
// the planner buffer can dynamically change the velocity profile data as blocks are added.
st_prep_data = &segment_data[st_data_prep_index];
// Initialize planner block step data
st_prep_data->step_events_remaining = pl_prep_block->step_event_count;
st_prep_data->step_per_mm = pl_prep_block->step_event_count/pl_prep_block->millimeters;
st_prep_data->dist_per_step = ceil(INV_TIME_MULTIPLIER/st_prep_data->step_per_mm); // (mult*mm/step)
st_prep_data->acceleration = st_prep_data->step_per_mm*pl_prep_block->acceleration;
}
// Convert planner entry speed to stepper initial rate.
st_prep_data->current_rate = st_prep_data->step_per_mm*sqrt(pl_prep_block->entry_speed_sqr);
// Determine current block exit speed
plan_block_t *pl_next_block = plan_get_block_by_index(plan_next_block_index(pl_prep_index));
float exit_speed_sqr;
if (pl_next_block != NULL) {
exit_speed_sqr = pl_next_block->entry_speed_sqr;
st_prep_data->exit_rate = st_prep_data->step_per_mm*sqrt(exit_speed_sqr);
} else {
exit_speed_sqr = 0.0; // End of planner buffer. Zero speed.
st_prep_data->exit_rate = 0.0;
}
// Determine velocity profile based on the 7 possible types: Cruise-only, cruise-deceleration,
// acceleration-cruise, acceleration-only, deceleration-only, trapezoid, and triangle.
st_prep_data->accelerate_until = pl_prep_block->millimeters;
if (pl_prep_block->entry_speed_sqr == pl_prep_block->nominal_speed_sqr) {
st_prep_data->maximum_rate = sqrt(pl_prep_block->nominal_speed_sqr);
st_prep_data->accelerate_until = pl_prep_block->millimeters;
if (exit_speed_sqr == pl_prep_block->nominal_speed_sqr) { // Cruise-only type
st_prep_data->decelerate_after = 0.0;
} else { // Cruise-deceleration type
st_prep_data->decelerate_after = (pl_prep_block->nominal_speed_sqr-exit_speed_sqr)/(2*pl_prep_block->acceleration);
}
} else if (exit_speed_sqr == pl_prep_block->nominal_speed_sqr) {
// Acceleration-cruise type
st_prep_data->maximum_rate = sqrt(pl_prep_block->nominal_speed_sqr);
st_prep_data->decelerate_after = 0.0;
st_prep_data->accelerate_until -= (pl_prep_block->nominal_speed_sqr-pl_prep_block->entry_speed_sqr)/(2*pl_prep_block->acceleration);
} else {
float intersection_dist = 0.5*( pl_prep_block->millimeters + (pl_prep_block->entry_speed_sqr
- exit_speed_sqr)/(2*pl_prep_block->acceleration) );
if (intersection_dist > 0.0) {
if (intersection_dist < pl_prep_block->millimeters) { // Either trapezoid or triangle types
st_prep_data->decelerate_after = (pl_prep_block->nominal_speed_sqr-exit_speed_sqr)/(2*pl_prep_block->acceleration);
if (st_prep_data->decelerate_after < intersection_dist) { // Trapezoid type
st_prep_data->maximum_rate = sqrt(pl_prep_block->nominal_speed_sqr);
st_prep_data->accelerate_until -= (pl_prep_block->nominal_speed_sqr-pl_prep_block->entry_speed_sqr)/(2*pl_prep_block->acceleration);
} else { // Triangle type
st_prep_data->decelerate_after = intersection_dist;
st_prep_data->maximum_rate = sqrt(2*pl_prep_block->acceleration*st_prep_data->decelerate_after+exit_speed_sqr);
st_prep_data->accelerate_until -= st_prep_data->decelerate_after;
}
} else { // Deceleration-only type
st_prep_data->maximum_rate = sqrt(pl_prep_block->entry_speed_sqr);
st_prep_data->decelerate_after = pl_prep_block->millimeters;
}
} else { // Acceleration-only type
st_prep_data->maximum_rate = sqrt(exit_speed_sqr);
st_prep_data->decelerate_after = 0.0;
st_prep_data->accelerate_until = 0.0;
}
}
// Determine block velocity profile parameters
// st_prep_data->accelerate_until = (pl_prep_block->nominal_speed_sqr-pl_prep_block->entry_speed_sqr)/(2*pl_prep_block->acceleration);
// st_prep_data->decelerate_after = (pl_prep_block->nominal_speed_sqr-exit_speed_sqr)/(2*pl_prep_block->acceleration);
//
// // Determine if velocity profile is a triangle or trapezoid.
// if (pl_prep_block->millimeters < st_prep_data->accelerate_until+st_prep_data->decelerate_after) {
// st_prep_data->decelerate_after = 0.5*( pl_prep_block->millimeters + (pl_prep_block->entry_speed_sqr
// - exit_speed_sqr)/(2*pl_prep_block->acceleration) );
// st_prep_data->accelerate_until = pl_prep_block->millimeters-st_prep_data->decelerate_after;
// st_prep_data->maximum_speed = sqrt(2*pl_prep_block->acceleration*st_prep_data->decelerate_after+exit_speed_sqr);
// } else {
// st_prep_data->accelerate_until = pl_prep_block->millimeters-st_prep_data->accelerate_until;
// st_prep_data->maximum_speed = sqrt(pl_prep_block->nominal_speed_sqr);
// }
// Convert velocity profile parameters in terms of steps.
st_prep_data->maximum_rate *= st_prep_data->step_per_mm;
st_prep_data->accelerate_until *= st_prep_data->step_per_mm;
st_prep_data->decelerate_after *= st_prep_data->step_per_mm;
}
// Set new segment to point to the current segment data block.
prep_segment->st_data_index = st_data_prep_index;
// -----------------------------------------------------------------------------------
// Initialize segment execute distance. Attempt to create a full segment over DT_SEGMENT.
// NOTE: Computed in terms of steps and seconds to prevent numerical round-off issues.
float steps_remaining = st_prep_data->step_events_remaining;
float dt = DT_SEGMENT;
if (steps_remaining > st_prep_data->accelerate_until) { // Acceleration ramp
steps_remaining -= st_prep_data->current_rate*DT_SEGMENT
+ st_prep_data->acceleration*(0.5*DT_SEGMENT*DT_SEGMENT);
if (steps_remaining < st_prep_data->accelerate_until) { // **Incomplete** Acceleration ramp end.
// Acceleration-cruise, acceleration-deceleration ramp junction, or end of block
steps_remaining = st_prep_data->accelerate_until;
dt = 2*(st_prep_data->step_events_remaining-steps_remaining)/
(st_prep_data->current_rate+st_prep_data->maximum_rate);
st_prep_data->current_rate = st_prep_data->maximum_rate;
} else { // **Complete** Acceleration only.
st_prep_data->current_rate += st_prep_data->acceleration*DT_SEGMENT;
}
} else if (steps_remaining <= st_prep_data->decelerate_after) { // Deceleration ramp
steps_remaining -= st_prep_data->current_rate*DT_SEGMENT
- st_prep_data->acceleration*(0.5*DT_SEGMENT*DT_SEGMENT);
if (steps_remaining > 0) { // **Complete** Deceleration only.
st_prep_data->current_rate -= st_prep_data->acceleration*DT_SEGMENT;
} else { // **Complete* End of block.
dt = 2*st_prep_data->step_events_remaining/(st_prep_data->current_rate+st_prep_data->exit_rate);
steps_remaining = 0;
// st_prep_data->current_speed = st_prep_data->exit_speed;
}
} else { // Cruising profile
steps_remaining -= st_prep_data->maximum_rate*DT_SEGMENT;
if (steps_remaining < st_prep_data->decelerate_after) { // **Incomplete** End of cruise.
steps_remaining = st_prep_data->decelerate_after;
dt = (st_prep_data->step_events_remaining-steps_remaining)/st_prep_data->maximum_rate;
} // Otherwise **Complete** Cruising only.
}
// -----------------------------------------------------------------------------------
// If segment is incomplete, attempt to fill the remainder.
// NOTE: Segment remainder always spans a cruise and/or a deceleration ramp.
if (dt < DT_SEGMENT) {
if (steps_remaining > 0) { // Skip if end of block.
float last_steps_remaining;
// Fill incomplete segment with an acceleration junction.
if (steps_remaining > st_prep_data->decelerate_after) { // Cruising profile
last_steps_remaining = steps_remaining;
steps_remaining -= st_prep_data->current_rate*(DT_SEGMENT-dt);
if (steps_remaining < st_prep_data->decelerate_after) { // **Incomplete**
steps_remaining = st_prep_data->decelerate_after;
dt += (last_steps_remaining-steps_remaining)/st_prep_data->maximum_rate;
// current_speed = maximum_speed;
} else { // **Complete** Segment filled.
dt = DT_SEGMENT;
}
}
// Fill incomplete segment with a deceleration junction.
if (steps_remaining > 0) {
if (steps_remaining <= st_prep_data->decelerate_after) { // Deceleration ramp
last_steps_remaining = steps_remaining;
float dt_remainder = DT_SEGMENT-dt;
steps_remaining -= dt_remainder*(st_prep_data->current_rate
- 0.5*st_prep_data->acceleration*dt_remainder);
if (steps_remaining > 0) { // **Complete** Segment filled.
st_prep_data->current_rate -= st_prep_data->acceleration*dt_remainder;
dt = DT_SEGMENT;
} else { // **Complete** End of block.
steps_remaining = 0;
dt += (2*last_steps_remaining/(st_prep_data->current_rate+st_prep_data->exit_rate));
// st_prep_data->current_speed = st_prep_data->exit_speed;
}
}
}
}
}
// -----------------------------------------------------------------------------------
// Compute segment step rate, steps to execute, and step phase correction parameters.
// NOTE:
// !!! PROBLEM. Step events remaining in floating point can limit the number of steps
// we can accurately track, since floats have 8 significant digits. However, this only
// becomes a problem if there are more than 10,000,000, which translates to a CNC machine
// with 800 step/mm and 10 meters of axis travel.
prep_segment->dist_per_tick = ceil((st_prep_data->step_events_remaining-steps_remaining)
/dt*(INV_TIME_MULTIPLIER/ISR_TICKS_PER_SECOND)); // (mult*mm/isr_tic)
if (steps_remaining > 0) {
// Compute number of steps to execute and segment step phase correction.
prep_segment->n_step = ceil(st_prep_data->step_events_remaining)-ceil(steps_remaining);
prep_segment->n_phase_tick = ceil((ceil(steps_remaining)-steps_remaining)*st_prep_data->dist_per_step);
} else { // End of block. Finish it out.
// Set to execute the remaining steps and no phase correction upon finishing the block.
prep_segment->n_step = ceil(st_prep_data->step_events_remaining);
prep_segment->n_phase_tick = 0;
// Move planner pointer to next block and flag to load a new block for the next segment.
pl_prep_index = plan_next_block_index(pl_prep_index);
pl_prep_block = NULL;
prep_segment->flag |= SEGMENT_END_OF_BLOCK;
}
// Update step execution variables
st_prep_data->step_events_remaining = steps_remaining;
// Ensure the initial step rate exceeds the MINIMUM_STEP_RATE.
// TODO: Use config.h error checking to do this. Otherwise, counters get screwy.
// New step segment initialization completed. Increment segment buffer indices.
segment_buffer_head = segment_next_head;
if ( ++segment_next_head == SEGMENT_BUFFER_SIZE ) { segment_next_head = 0; }
SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
}
}
uint8_t st_get_prep_block_index()
{
// Returns only the index but doesn't state if the block has been partially executed. How do we simply check for this?
return(pl_prep_index);
}
void st_fetch_partial_block_parameters(uint8_t block_index, float *millimeters_remaining, uint8_t *is_decelerating)
{
// if called, can we assume that this always changes and needs to be updated? if so, then
// we can perform all of the segment buffer setup tasks here to make sure the next time
// the segments are loaded, the st_data buffer is updated correctly.
// !!! Make sure that this is always pointing to the correct st_prep_data block.
// When a mid-block acceleration occurs, we have to make sure the ramp counters are updated
// correctly, much in the same fashion as the deceleration counters. Need to think about this
// make sure this is right, but i'm pretty sure it is.
// TODO: NULL means that the segment buffer has just completed a planner block. Clean up!
if (pl_prep_block != NULL) {
*millimeters_remaining = st_prep_data->step_events_remaining/st_prep_data->step_per_mm;
if (st_prep_data->step_events_remaining < st_prep_data->decelerate_after) { *is_decelerating = true; }
else { *is_decelerating = false; }
// Flag for new prep_block when st_prep_buffer() is called after the planner recomputes.
pl_partial_block_flag = true;
pl_prep_block = NULL;
}
return;
}

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archive/stepper_time_archive.c
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@ -1,823 +0,0 @@
/*
stepper.c - stepper motor driver: executes motion plans using stepper motors
Part of Grbl
Copyright (c) 2011-2013 Sungeun K. Jeon
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/>.
*/
#include <avr/interrupt.h>
#include "stepper.h"
#include "config.h"
#include "settings.h"
#include "planner.h"
#include "nuts_bolts.h"
// Some useful constants
#define TICKS_PER_MICROSECOND (F_CPU/1000000)
#define RAMP_ACCEL 0
#define RAMP_CRUISE 1
#define RAMP_DECEL 2
#define LOAD_NOOP 0
#define LOAD_SEGMENT 1
#define LOAD_BLOCK 2
#define SEGMENT_NOOP 0
#define SEGMENT_END_OF_BLOCK bit(0)
#define RAMP_CHANGE_ACCEL bit(1)
#define RAMP_CHANGE_DECEL bit(2)
#define SEGMENT_BUFFER_SIZE 6
#define DT_SEGMENT (1.0/(ACCELERATION_TICKS_PER_SECOND*60.0))
// Stores the planner block Bresenham algorithm execution data for the segments in the segment
// buffer. Normally, this buffer is partially in-use, but, for the worst case scenario, it will
// never exceed the number of accessible stepper buffer segments (SEGMENT_BUFFER_SIZE-1).
// NOTE: This data is copied from the prepped planner blocks so that the planner blocks may be
// discarded when entirely consumed and completed by the segment buffer.
typedef struct {
uint8_t direction_bits;
int32_t steps[N_AXIS];
int32_t step_event_count;
} st_block_t;
static st_block_t st_block_buffer[SEGMENT_BUFFER_SIZE-1];
// TODO: Directly adjust this parameters to stop motion of individual axes for the homing cycle.
// But this may require this to be volatile if it is controlled by an interrupt.
// Primary stepper segment ring buffer. Contains small, short line segments for the stepper
// algorithm to execute, which are "checked-out" incrementally from the first block in the
// planner buffer. Once "checked-out", the steps in the segments buffer cannot be modified by
// the planner, where the remaining planner block steps still can.
typedef struct {
uint8_t n_step; // Number of step events to be executed for this segment
uint8_t st_block_index; // Stepper block data index. Uses this information to execute this segment.
int32_t phase_dist;
int32_t dist_per_tick;
} segment_t;
static segment_t segment_buffer[SEGMENT_BUFFER_SIZE];
// Stepper state variable. Contains running data and trapezoid variables.
typedef struct {
// Used by the bresenham line algorithm
int32_t counter_x, // Counter variables for the bresenham line tracer
counter_y,
counter_z;
// Used by inverse time algorithm to track step rate
int32_t counter_dist; // Inverse time distance traveled since last step event
// Used by the stepper driver interrupt
uint8_t execute_step; // Flags step execution for each interrupt.
uint8_t step_pulse_time; // Step pulse reset time after step rise
uint8_t out_bits; // The next stepping-bits to be output
uint8_t step_count; // Steps remaining in line segment motion
uint8_t exec_block_index; // Tracks the current st_block index. Change indicates new block.
st_block_t *exec_block; // Pointer to the block data for the segment being executed
segment_t *exec_segment; // Pointer to the segment being executed
} stepper_t;
static stepper_t st;
// Step segment ring buffer indices
static volatile uint8_t segment_buffer_tail;
static volatile uint8_t segment_buffer_head;
static uint8_t segment_next_head;
static volatile uint8_t busy; // Used to avoid ISR nesting of the "Stepper Driver Interrupt". Should never occur though.
// Pointers for the step segment being prepped from the planner buffer. Accessed only by the
// main program. Pointers may be planning segments or planner blocks ahead of what being executed.
static plan_block_t *pl_block; // Pointer to the planner block being prepped
static st_block_t *st_prep_block; // Pointer to the stepper block data being prepped
typedef struct {
uint8_t st_block_index; // Index of stepper common data block being prepped
uint8_t partial_block_flag; // Flag indicating the planner has modified the prepped planner block
float step_per_mm;
float step_events_remaining; // Tracks step event count for the executing planner block
// int32_t step_events_remaining;
float step_remainder;
uint8_t ramp_type;
float current_speed;
float maximum_speed;
float exit_speed;
float accelerate_until;
float decelerate_after;
} st_prep_t;
static st_prep_t prep;
/* __________________________
/| |\ _________________ ^
/ | | \ /| |\ |
/ | | \ / | | \ s
/ | | | | | \ p
/ | | | | | \ e
+-----+------------------------+---+--+---------------+----+ e
| BLOCK 1 | BLOCK 2 | d
time ----->
The trapezoid is the shape the speed curve over time. It starts at block->initial_rate, accelerates by block->rate_delta
until reaching cruising speed block->nominal_rate, and/or until step_events_remaining reaches block->decelerate_after
after which it decelerates until the block is completed. The driver uses constant acceleration, which is applied as
+/- block->rate_delta velocity increments by the midpoint rule at each ACCELERATION_TICKS_PER_SECOND.
*/
// Stepper state initialization. Cycle should only start if the st.cycle_start flag is
// enabled. Startup init and limits call this function but shouldn't start the cycle.
void st_wake_up()
{
// Enable steppers by resetting the stepper disable port
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
}
if (sys.state == STATE_CYCLE) {
// Initialize stepper output bits
st.out_bits = settings.invert_mask;
// Initialize step pulse timing from settings.
st.step_pulse_time = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND) >> 3);
// Enable stepper driver interrupt
TCNT2 = 0; // Clear Timer2
TIMSK2 |= (1<<OCIE2A); // Enable Timer2 Compare Match A interrupt
TCCR2B = (1<<CS21); // Begin Timer2. Full speed, 1/8 prescaler
}
}
// Stepper shutdown
void st_go_idle()
{
// Disable stepper driver interrupt. Allow Timer0 to finish. It will disable itself.
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt
TCCR2B = 0; // Disable Timer2
busy = false;
// Disable steppers only upon system alarm activated or by user setting to not be kept enabled.
if ((settings.stepper_idle_lock_time != 0xff) || bit_istrue(sys.execute,EXEC_ALARM)) {
// Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
// stop and not drift from residual inertial forces at the end of the last movement.
delay_ms(settings.stepper_idle_lock_time);
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
}
}
}
/* "The Stepper Driver Interrupt" - This timer interrupt is the workhorse of Grbl. It is based
on an inverse time stepper algorithm, where a timer ticks at a constant frequency and uses
time-distance counters to track when its the approximate time for a step event. For reference,
a similar inverse-time algorithm by Pramod Ranade is susceptible to numerical round-off, as
described, meaning that some axes steps may not execute correctly for a given multi-axis motion.
Grbl's algorithm differs by using a single inverse time-distance counter to manage a
Bresenham line algorithm for multi-axis step events, which ensures the number of steps for
each axis are executed exactly. In other words, Grbl uses a Bresenham within a Bresenham
algorithm, where one tracks time for step events and the other steps for multi-axis moves.
Grbl specifically uses the Bresenham algorithm due to its innate mathematical exactness and
low computational overhead, requiring simple integer +,- counters only.
This interrupt pops blocks from the step segment buffer and executes them by pulsing the
stepper pins appropriately. It is supported by The Stepper Port Reset Interrupt which it uses
to reset the stepper port after each pulse. The bresenham line tracer algorithm controls all
three stepper outputs simultaneously with these two interrupts.
*/
/* TODO:
- Measure time in ISR. Typical and worst-case. Should be virtually identical to last algorithm.
There are no major changes to the base operations of this ISR with the new segment buffer.
- Determine if placing the position counters elsewhere (or change them to 8-bit variables that
are added to the system position counters at the end of a segment) frees up cycles.
- Create NOTE: to describe that the total time in this ISR must be less than the ISR frequency
in its worst case scenario.
*/
ISR(TIMER2_COMPA_vect)
{
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
if (busy) { return; } // The busy-flag is used to avoid reentering this interrupt
// Pulse stepper port pins, if flagged. New block dir will always be set one timer tick
// before any step pulse due to algorithm design.
if (st.execute_step) {
st.execute_step = false;
STEPPING_PORT = ( STEPPING_PORT & ~(DIRECTION_MASK | STEP_MASK) ) | st.out_bits;
TCNT0 = st.step_pulse_time; // Reload Timer0 counter.
TCCR0B = (1<<CS21); // Begin Timer0. Full speed, 1/8 prescaler
}
busy = true;
sei(); // Re-enable interrupts to allow Stepper Port Reset Interrupt to fire on-time.
// NOTE: The remaining code in this ISR will finish before returning to main program.
// If there is no step segment, attempt to pop one from the stepper buffer
if (st.exec_segment == NULL) {
// Anything in the buffer? If so, load and initialize next step segment.
if (segment_buffer_head != segment_buffer_tail) {
// Initialize new step segment and load number of steps to execute
st.exec_segment = &segment_buffer[segment_buffer_tail];
st.step_count = st.exec_segment->n_step;
// If the new segment starts a new planner block, initialize stepper variables and counters.
// NOTE: When the segment data index changes, this indicates a new planner block.
if ( st.exec_block_index != st.exec_segment->st_block_index ) {
st.exec_block_index = st.exec_segment->st_block_index;
st.exec_block = &st_block_buffer[st.exec_block_index];
// Initialize direction bits for block. Set execute flag to set directions bits upon next ISR tick.
st.out_bits = st.exec_block->direction_bits ^ settings.invert_mask;
st.execute_step = true;
// Initialize Bresenham line counters
st.counter_x = (st.exec_block->step_event_count >> 1);
st.counter_y = st.counter_x;
st.counter_z = st.counter_x;
// Initialize inverse time, step rate data, and acceleration ramp counters
st.counter_dist = INV_TIME_MULTIPLIER; // dist_per_step always greater than dist_per_tick.
}
} else {
// Segment buffer empty. Shutdown.
st_go_idle();
bit_true(sys.execute,EXEC_CYCLE_STOP); // Flag main program for cycle end
return; // Nothing to do but exit.
}
}
// Iterate inverse time counter. Triggers each Bresenham step event.
st.counter_dist -= st.exec_segment->dist_per_tick;
// Execute Bresenham step event, when it's time to do so.
if (st.counter_dist < 0) {
if (st.step_count != 0) { // Block phase correction from executing step.
st.counter_dist += INV_TIME_MULTIPLIER; // Reload inverse time counter
st.step_count--; // Decrement step events count
// Execute step displacement profile by Bresenham line algorithm
st.execute_step = true;
st.out_bits = st.exec_block->direction_bits; // Reset out_bits and reload direction bits
st.counter_x -= st.exec_block->steps[X_AXIS];
if (st.counter_x < 0) {
st.out_bits |= (1<<X_STEP_BIT);
st.counter_x += st.exec_block->step_event_count;
if (st.out_bits & (1<<X_DIRECTION_BIT)) { sys.position[X_AXIS]--; }
else { sys.position[X_AXIS]++; }
}
st.counter_y -= st.exec_block->steps[Y_AXIS];
if (st.counter_y < 0) {
st.out_bits |= (1<<Y_STEP_BIT);
st.counter_y += st.exec_block->step_event_count;
if (st.out_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS]--; }
else { sys.position[Y_AXIS]++; }
}
st.counter_z -= st.exec_block->steps[Z_AXIS];
if (st.counter_z < 0) {
st.out_bits |= (1<<Z_STEP_BIT);
st.counter_z += st.exec_block->step_event_count;
if (st.out_bits & (1<<Z_DIRECTION_BIT)) { sys.position[Z_AXIS]--; }
else { sys.position[Z_AXIS]++; }
}
st.out_bits ^= settings.invert_mask; // Apply step port invert mask
}
}
if (st.step_count == 0) {
if (st.exec_segment->phase_dist > st.counter_dist) {
// Segment is complete. Discard current segment and advance segment indexing.
st.exec_segment = NULL;
if ( ++segment_buffer_tail == SEGMENT_BUFFER_SIZE) { segment_buffer_tail = 0; }
}
}
busy = false;
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
}
/* The Stepper Port Reset Interrupt: Timer0 OVF interrupt handles the falling edge of the step
pulse. This should always trigger before the next Timer2 COMPA interrupt and independently
finish, if Timer2 is disabled after completing a move. */
ISR(TIMER0_OVF_vect)
{
STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | (settings.invert_mask & STEP_MASK);
TCCR0B = 0; // Disable timer until needed.
}
// Reset and clear stepper subsystem variables
void st_reset()
{
memset(&prep, 0, sizeof(prep));
memset(&st, 0, sizeof(st));
st.exec_segment = NULL;
pl_block = NULL; // Planner block pointer used by segment buffer
segment_buffer_tail = 0;
segment_buffer_head = 0; // empty = tail
segment_next_head = 1;
busy = false;
}
// Initialize and start the stepper motor subsystem
void st_init()
{
// Configure directions of interface pins
STEPPING_DDR |= STEPPING_MASK;
STEPPING_PORT = (STEPPING_PORT & ~STEPPING_MASK) | settings.invert_mask;
STEPPERS_DISABLE_DDR |= 1<<STEPPERS_DISABLE_BIT;
// Configure Timer 2
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt while configuring it
TCCR2B = 0; // Disable Timer2 until needed
TCNT2 = 0; // Clear Timer2 counter
TCCR2A = (1<<WGM21); // Set CTC mode
OCR2A = (F_CPU/ISR_TICKS_PER_SECOND)/8 - 1; // Set Timer2 CTC rate
// Configure Timer 0
TIMSK0 &= ~(1<<TOIE0);
TCCR0A = 0; // Normal operation
TCCR0B = 0; // Disable Timer0 until needed
TIMSK0 |= (1<<TOIE0); // Enable overflow interrupt
// Start in the idle state, but first wake up to check for keep steppers enabled option.
st_wake_up();
st_go_idle();
}
// Planner external interface to start stepper interrupt and execute the blocks in queue. Called
// by the main program functions: planner auto-start and run-time command execution.
void st_cycle_start()
{
if (sys.state == STATE_QUEUED) {
sys.state = STATE_CYCLE;
st_prep_buffer(); // Initialize step segment buffer before beginning cycle.
st_wake_up();
}
}
// Execute a feed hold with deceleration, only during cycle. Called by main program.
void st_feed_hold()
{
if (sys.state == STATE_CYCLE) {
sys.state = STATE_HOLD;
sys.auto_start = false; // Disable planner auto start upon feed hold.
}
}
// Reinitializes the cycle plan and stepper system after a feed hold for a resume. Called by
// runtime command execution in the main program, ensuring that the planner re-plans safely.
// NOTE: Bresenham algorithm variables are still maintained through both the planner and stepper
// cycle reinitializations. The stepper path should continue exactly as if nothing has happened.
// Only the planner de/ac-celerations profiles and stepper rates have been updated.
void st_cycle_reinitialize()
{
// if (pl_current_block != NULL) {
// plan_cycle_reinitialize(st_exec_block->step_events_remaining);
// st.ramp_type = RAMP_ACCEL;
// st.counter_ramp = ISR_TICKS_PER_ACCELERATION_TICK/2;
// st.ramp_rate = 0;
// sys.state = STATE_QUEUED;
// } else {
// sys.state = STATE_IDLE;
// }
sys.state = STATE_IDLE;
}
/* Prepares step segment buffer. Continuously called from main program.
The segment buffer is an intermediary buffer interface between the execution of steps
by the stepper algorithm and the velocity profiles generated by the planner. The stepper
algorithm only executes steps within the segment buffer and is filled by the main program
when steps are "checked-out" from the first block in the planner buffer. This keeps the
step execution and planning optimization processes atomic and protected from each other.
The number of steps "checked-out" from the planner buffer and the number of segments in
the segment buffer is sized and computed such that no operation in the main program takes
longer than the time it takes the stepper algorithm to empty it before refilling it.
Currently, the segment buffer conservatively holds roughly up to 40-60 msec of steps.
NOTE: The segment buffer executes a set number of steps over an approximate time period.
If we try to execute over a fixed time period, it is difficult to guarantee or predict
how many steps will execute over it, especially when the step pulse phasing between the
neighboring segments must also be kept consistent. Meaning that, if the last segment step
pulses right before a segment end, the next segment must delay its first pulse so that the
step pulses are consistently spaced apart over time to keep the step pulse train nice and
smooth. Keeping track of phasing and ensuring that the exact number of steps are executed
as defined by the planner block, the related computational overhead can get quickly and
prohibitively expensive, especially in real-time.
Since the stepper algorithm automatically takes care of the step pulse phasing with
its ramp and inverse time counters by retaining the count remainders, we don't have to
explicitly and expensively track and synchronize the exact number of steps, time, and
phasing of steps. All we need to do is approximate the number of steps in each segment
such that the segment buffer has enough execution time for the main program to do what
it needs to do and refill it when it comes back. In other words, we just need to compute
a cheap approximation of the current velocity and the number of steps over it.
*/
/*
TODO: Figure out how to enforce a deceleration when a feedrate override is reduced.
The problem is that when an override is reduced, the planner may not plan back to
the current rate. Meaning that the velocity profiles for certain conditions no longer
are trapezoidal or triangular. For example, if the current block is cruising at a
nominal rate and the feedrate override is reduced, the new nominal rate will now be
lower. The velocity profile must first decelerate to the new nominal rate and then
follow on the new plan. So the remaining velocity profile will have a decelerate,
cruise, and another decelerate.
Another issue is whether or not a feedrate override reduction causes a deceleration
that acts over several planner blocks. For example, say that the plan is already
heavily decelerating throughout it, reducing the feedrate will not do much to it. So,
how do we determine when to resume the new plan? How many blocks do we have to wait
until the new plan intersects with the deceleration curve? One plus though, the
deceleration will never be more than the number of blocks in the entire planner buffer,
but it theoretically can be equal to it when all planner blocks are decelerating already.
*/
void st_prep_buffer()
{
if (sys.state == STATE_QUEUED) { return; } // Block until a motion state is issued
while (segment_buffer_tail != segment_next_head) { // Check if we need to fill the buffer.
// -----------------------------------------------------------------------------------
// Determine if we need to load a new planner block. If so, prepare step data.
if (pl_block == NULL) {
pl_block = plan_get_current_block(); // Query planner for a queued block
if (pl_block == NULL) { return; } // No planner blocks. Exit.
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
// Check if the planner has re-computed this block mid-execution.
if (prep.partial_block_flag) {
// Retain last Bresenham data, but recompute the velocity profile.
prep.partial_block_flag = false; // Reset flag
} else {
// Increment stepper common data index
if ( ++prep.st_block_index == (SEGMENT_BUFFER_SIZE-1) ) { prep.st_block_index = 0; }
// Prepare and copy Bresenham algorithm segment data from the new planner block, so that
// when the segment buffer completes the planner block, it may be discarded immediately.
st_prep_block = &st_block_buffer[prep.st_block_index];
st_prep_block->steps[X_AXIS] = pl_block->steps[X_AXIS];
st_prep_block->steps[Y_AXIS] = pl_block->steps[Y_AXIS];
st_prep_block->steps[Z_AXIS] = pl_block->steps[Z_AXIS];
st_prep_block->direction_bits = pl_block->direction_bits;
st_prep_block->step_event_count = pl_block->step_event_count;
// Initialize planner block step count, unit distance data, and remainder tracker.
prep.step_per_mm = ((float)st_prep_block->step_event_count)/pl_block->millimeters;
prep.step_events_remaining = st_prep_block->step_event_count;
prep.step_remainder = 0.0;
}
// Compute the prepped planner block velocity profile to be traced by stepper algorithm.
prep.current_speed = sqrt(pl_block->entry_speed_sqr);
prep.exit_speed = plan_get_exec_block_exit_speed();
// Determine velocity profile based on the 7 possible types: Cruise-only, cruise-deceleration,
// acceleration-cruise, acceleration-only, deceleration-only, full-trapezoid, and triangle.
prep.ramp_type = RAMP_ACCEL;
float exit_speed_sqr = prep.exit_speed*prep.exit_speed;
float inv_2_accel = 0.5/pl_block->acceleration;
float intersection_dist =
0.5*(pl_block->millimeters+inv_2_accel*(pl_block->entry_speed_sqr-exit_speed_sqr));
if (intersection_dist > 0.0) {
if (intersection_dist < pl_block->millimeters) { // Either trapezoid or triangle types
// NOTE: For acceleration-cruise trapezoid, following calculation will be 0.0.
prep.decelerate_after = inv_2_accel*(pl_block->nominal_speed_sqr-exit_speed_sqr);
if (prep.decelerate_after < intersection_dist) { // Trapezoid type
prep.maximum_speed = sqrt(pl_block->nominal_speed_sqr);
if (pl_block->entry_speed_sqr == pl_block->nominal_speed_sqr) {
// Cruise-deceleration or cruise-only type.
prep.ramp_type = RAMP_CRUISE;
prep.accelerate_until = pl_block->millimeters;
} else {
// Full-trapezoid or acceleration-cruise types
prep.accelerate_until =
pl_block->millimeters-inv_2_accel*(pl_block->nominal_speed_sqr-pl_block->entry_speed_sqr);
}
} else { // Triangle type
prep.accelerate_until = intersection_dist;
prep.decelerate_after = intersection_dist;
prep.maximum_speed = sqrt(2.0*pl_block->acceleration*intersection_dist+exit_speed_sqr);
}
} else { // Deceleration-only type
prep.ramp_type = RAMP_DECEL;
prep.maximum_speed = prep.current_speed;
prep.accelerate_until = pl_block->millimeters;
prep.decelerate_after = pl_block->millimeters;
}
} else { // Acceleration-only type
prep.maximum_speed = prep.exit_speed;
prep.accelerate_until = 0.0;
prep.decelerate_after = 0.0;
}
}
// Initialize new segment
segment_t *prep_segment = &segment_buffer[segment_buffer_head];
// Set new segment to point to the current segment data block.
prep_segment->st_block_index = prep.st_block_index;
/* -----------------------------------------------------------------------------------
Compute the average velocity of this new segment by determining the total distance
traveled over the segment time DT_SEGMENT. This section attempts to create a full
segment based on the current ramp conditions. If the segment is incomplete and
terminates upon a ramp change, the next section will attempt to fill the remaining
segment execution time. However, if an incomplete segment terminates at the end of
the planner block, the segment execution time is less than DT_SEGMENT and the new
segment will execute over this truncated execution time.
*/
float dt = 0.0;
float mm_remaining = pl_block->millimeters;
float dt_var = DT_SEGMENT;
float mm_var;
do {
switch (prep.ramp_type) {
case RAMP_ACCEL:
// NOTE: Acceleration ramp always computes during first loop only.
mm_remaining -= DT_SEGMENT*(prep.current_speed + pl_block->acceleration*(0.5*DT_SEGMENT));
if (mm_remaining < prep.accelerate_until) { // End of acceleration ramp.
// Acceleration-cruise, acceleration-deceleration ramp junction, or end of block.
mm_remaining = prep.accelerate_until; // NOTE: 0.0 at EOB
dt_var = 2.0*(pl_block->millimeters-mm_remaining)/(prep.current_speed+prep.maximum_speed);
if (mm_remaining == prep.decelerate_after) { prep.ramp_type = RAMP_DECEL; }
else { prep.ramp_type = RAMP_CRUISE; }
prep.current_speed = prep.maximum_speed;
} else { // Acceleration only.
prep.current_speed += pl_block->acceleration*dt_var;
}
break;
case RAMP_CRUISE:
// NOTE: mm_var used to retain the last mm_remaining for incomplete segment dt_var calculations.
mm_var = mm_remaining - prep.maximum_speed*dt_var;
if (mm_var < prep.decelerate_after) { // End of cruise.
// Cruise-deceleration junction or end of block.
dt_var = (mm_remaining - prep.decelerate_after)/prep.maximum_speed;
mm_remaining = prep.decelerate_after; // NOTE: 0.0 at EOB
prep.ramp_type = RAMP_DECEL;
} else { // Cruising only.
mm_remaining = mm_var;
}
break;
default: // case RAMP_DECEL:
// NOTE: mm_var used to catch negative decelerate distance values near zero speed.
mm_var = dt_var*(prep.current_speed - 0.5*pl_block->acceleration*dt_var);
if ((mm_var > 0.0) && (mm_var < pl_block->millimeters)) { // Deceleration only.
prep.current_speed -= pl_block->acceleration*dt_var;
// Check for near-zero speed and prevent divide by zero in rare scenarios.
if (prep.current_speed <= prep.exit_speed) { mm_remaining = 0.0; }
else { mm_remaining -= mm_var; }
} else { // End of block.
dt_var = 2.0*mm_remaining/(prep.current_speed+prep.exit_speed);
mm_remaining = 0.0;
// prep.current_speed = prep.exit_speed;
}
}
dt += dt_var;
if (dt < DT_SEGMENT) { dt_var = DT_SEGMENT - dt; } // **Incomplete** At ramp junction.
else { break; } // **Complete** Exit loop. Segment execution time maxed.
} while ( mm_remaining > 0.0 ); // **Complete** Exit loop. End of planner block.
/*
float mm_remaining;
float dt = DT_SEGMENT;
if (pl_block->millimeters > prep.accelerate_until) { // [Acceleration Ramp]
mm_remaining = pl_block->millimeters - DT_SEGMENT*(prep.current_speed + pl_block->acceleration*(0.5*DT_SEGMENT));
if (mm_remaining < prep.accelerate_until) { // **Incomplete** Acceleration ramp end.
// Acceleration-cruise, acceleration-deceleration ramp junction, or end of block.
mm_remaining = prep.accelerate_until; // NOTE: 0.0 at EOB
dt = 2.0*(pl_block->millimeters-mm_remaining)/(prep.current_speed+prep.maximum_speed);
prep.current_speed = prep.maximum_speed;
} else { // **Complete** Acceleration only.
prep.current_speed += pl_block->acceleration*DT_SEGMENT;
prep.current_speed = min(prep.maximum_speed,prep.current_speed);
}
} else if (pl_block->millimeters > prep.decelerate_after) { // [No Ramp. Cruising]
mm_remaining = pl_block->millimeters - prep.maximum_speed*DT_SEGMENT;
if (mm_remaining < prep.decelerate_after) { // **Incomplete** End of cruise.
// Cruise-deceleration junction or end of block.
mm_remaining = prep.decelerate_after; // NOTE: 0.0 at EOB
dt = (pl_block->millimeters-mm_remaining)/prep.maximum_speed;
} // Otherwise **Complete** Cruising only.
} else { // [Deceleration Ramp]
mm_remaining = DT_SEGMENT*(prep.current_speed - 0.5*pl_block->acceleration*DT_SEGMENT);
if ((mm_remaining > 0.0) && (mm_remaining < pl_block->millimeters)) { // **Complete** Deceleration only.
prep.current_speed -= pl_block->acceleration*DT_SEGMENT;
if (prep.current_speed <= prep.exit_speed) { // Round off error fix. Prevents divide by zero.
mm_remaining = 0.0;
} else {
mm_remaining = pl_block->millimeters - mm_remaining;
}
} else { // **Complete** End of block.
mm_remaining = 0.0;
dt = 2.0*pl_block->millimeters/(prep.current_speed+prep.exit_speed);
// prep.current_speed = prep.exit_speed;
}
}
/* -----------------------------------------------------------------------------------
If segment is incomplete, attempt to fill the remaining segment execution time.
NOTE: Segment remainder always spans a cruise and/or a deceleration ramp.
float partial_mm, dt_remainder;
if ((dt < DT_SEGMENT) && (mm_remaining > 0.0)) {
dt_remainder = DT_SEGMENT-dt;
// Attempt to fill incomplete segment with cruising profile.
if (mm_remaining > prep.decelerate_after) { // Cruising profile
partial_mm = mm_remaining - prep.current_speed*dt_remainder;
if (partial_mm < prep.decelerate_after) { // **Incomplete**
dt += (mm_remaining-prep.decelerate_after)/prep.maximum_speed;
mm_remaining = prep.decelerate_after;
// current_speed = maximum_speed;
} else { // **Complete** Segment filled.
mm_remaining = partial_mm;
dt = DT_SEGMENT;
}
}
// Attempt to fill incomplete segment with deceleration ramp.
if ((dt < DT_SEGMENT) && (mm_remaining > 0.0)) {
if (mm_remaining <= prep.decelerate_after) { // Deceleration ramp
dt_remainder = DT_SEGMENT-dt;
partial_mm = dt_remainder*(prep.current_speed-0.5*pl_block->acceleration*dt_remainder);
if ((partial_mm > 0.0) && (mm_remaining > partial_mm)) { // **Complete** Segment filled.
prep.current_speed -= pl_block->acceleration*dt_remainder;
if (prep.current_speed <= prep.exit_speed) {
mm_remaining = 0.0;
} else {
mm_remaining -= partial_mm;
dt = DT_SEGMENT;
}
} else { // **Complete** End of block.
dt += (2.0*mm_remaining/(prep.current_speed+prep.exit_speed));
mm_remaining = 0.0;
// prep.current_speed = prep.exit_speed;
}
}
}
}
*/
// printString(" Z");
// printFloat(dt*(60.0*1000.0));
// printString(" ");
// printFloat(mm_remaining);
// printString(" ");
// printFloat(prep.current_speed);
// printString("Z ");
/* -----------------------------------------------------------------------------------
Compute segment step rate, steps to execute, and step phase correction parameters.
*/
// float step_events;
// if (mm_remaining > 0.0) {
// step_events = prep.step_per_mm*(pl_block->millimeters - mm_remaining); // Convert mm to steps
// prep_segment->n_step = floor(step_events + prep.step_remainder);
// if (prep_segment->n_step > prep.step_events_remaining) { // Prevent round-off overshoot
// prep_segment->n_step = prep.step_events_remaining;
// }
// } else { // Ensure all remaining steps are executed
// step_events = prep.step_per_mm*pl_block->millimeters;
// prep_segment->n_step = prep.step_events_remaining;
// }
// prep.step_events_remaining -= prep_segment->n_step;
//
// // Compute segment rate.
// prep_segment->dist_per_tick =
// ceil( (INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND)) * (step_events/dt) ); // (mult*step/isr_tic)
//
// if (prep.step_events_remaining > 0) {
// // Compute step phase distance and update segment continuation parameters.
// prep.step_remainder += step_events - prep_segment->n_step;
// prep_segment->phase_dist = ceil(INV_TIME_MULTIPLIER-INV_TIME_MULTIPLIER*prep.step_remainder);
// pl_block->millimeters = mm_remaining;
// pl_block->entry_speed_sqr = prep.current_speed*prep.current_speed;
//
// } else { // End of block. Finish it out.
// // The planner block is complete. All steps are set to be executed in the segment buffer.
// // Move planner pointer to next block and flag to load a new block for the next segment.
// prep_segment->phase_dist = INV_TIME_MULTIPLIER;
// pl_block = NULL;
// plan_discard_current_block();
// }
if (mm_remaining > 0.0) {
float steps_remaining = prep.step_per_mm*mm_remaining;
prep_segment->dist_per_tick = ceil( (INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))*
((prep.step_events_remaining-steps_remaining)/dt) ); // (mult*step/isr_tic)
// Compute number of steps to execute and segment step phase correction.
prep_segment->n_step = ceil(prep.step_events_remaining)-ceil(steps_remaining);
prep_segment->phase_dist = ceil(INV_TIME_MULTIPLIER*(1.0-ceil(steps_remaining)+steps_remaining));
// Update step execution variables
prep.step_events_remaining = steps_remaining;
pl_block->millimeters = mm_remaining;
pl_block->entry_speed_sqr = prep.current_speed*prep.current_speed;
} else { // End of block. Finish it out.
prep_segment->dist_per_tick = ceil( (INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))*
prep.step_events_remaining/dt ); // (mult*step/isr_tic)
prep_segment->phase_dist = INV_TIME_MULTIPLIER;
// Set to execute the remaining steps and no phase correction upon finishing the block.
prep_segment->n_step = ceil(prep.step_events_remaining);
// NOTE: Not required. Planner will ignore this block as it is now complete.
// prep.step_events_remaining = 0.0;
// pl_block->millimeters = 0.0;
// The planner block is complete. All steps are set to be executed in the segment buffer.
// Move planner pointer to next block and flag to load a new block for the next segment.
pl_block = NULL;
plan_discard_current_block();
}
// long a = prep_segment->n_step;
// printInteger(a);
// printString(" ");
// a = prep_segment->phase_dist;
// printInteger(prep_segment->dist_per_tick);
// printString(" ");
// printFloat(prep.step_events_remaining);
// printString(" ");
// printFloat(pl_block->millimeters);
// printString(" ");
// !!! PROBLEM. Step events remaining in floating point can limit the number of steps
// we can accurately track, since floats have ~7.2 significant digits. However, this only
// becomes a problem if there are more than 1,000,000, which translates to a CNC machine
// with 200 step/mm and 5 meters of axis travel. Possible but unlikely. Could have more
// issues with user setting up their machine with too high of steps.
// TODO: dist_per_tick must be less than INV_TIME_MULTIPLIER. A check can be made to
// make this a hard limit. Need to make sure this doesn't affect the velocity profiles..
// it shouldn't. The same could said for the minimum allowable step rate too. This should
// not affect the tracing of the profiles either.
// Ensure the initial step rate exceeds the MINIMUM_STEP_RATE.
// TODO: Use config.h error checking to do this. Otherwise, counters get screwy.
// New step segment initialization completed. Increment segment buffer indices.
segment_buffer_head = segment_next_head;
if ( ++segment_next_head == SEGMENT_BUFFER_SIZE ) { segment_next_head = 0; }
int32_t blength = segment_buffer_head - segment_buffer_tail;
if (blength < 0) { blength += SEGMENT_BUFFER_SIZE; }
printInteger(blength);
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
}
}
// uint8_t st_get_prep_block_index()
// {
// // Returns only the index but doesn't state if the block has been partially executed. How do we simply check for this?
// return(prep.pl_block_index);
// }
void st_update_plan_block_parameters()
{
if (pl_block != NULL) { // Ignore if at start of a new block.
// Flag for new prep_block when st_prep_buffer() is called after the planner recomputes.
prep.partial_block_flag = true;
pl_block = NULL;
}
}

387
archive/stepper_v0_9.c
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@ -1,387 +0,0 @@
/*
stepper.c - stepper motor driver: executes motion plans using stepper motors
Part of Grbl
Copyright (c) 2011-2013 Sungeun K. Jeon
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/>.
*/
/* The timer calculations of this module informed by the 'RepRap cartesian firmware' by Zack Smith
and Philipp Tiefenbacher. */
#include <avr/interrupt.h>
#include "stepper.h"
#include "config.h"
#include "settings.h"
#include "planner.h"
// Some useful constants
#define TICKS_PER_MICROSECOND (F_CPU/1000000)
#define CRUISE_RAMP 0
#define ACCEL_RAMP 1
#define DECEL_RAMP 2
// Stepper state variable. Contains running data and trapezoid variables.
typedef struct {
// Used by the bresenham line algorithm
int32_t counter_x, // Counter variables for the bresenham line tracer
counter_y,
counter_z;
int32_t event_count; // Total event count. Retained for feed holds.
int32_t step_events_remaining; // Steps remaining in motion
// Used by Pramod Ranade inverse time algorithm
int32_t delta_d; // Ranade distance traveled per interrupt tick
int32_t d_counter; // Ranade distance traveled since last step event
uint8_t ramp_count; // Acceleration interrupt tick counter.
uint8_t ramp_type; // Ramp type variable.
uint8_t execute_step; // Flags step execution for each interrupt.
} stepper_t;
static stepper_t st;
static block_t *current_block; // A pointer to the block currently being traced
// Used by the stepper driver interrupt
static uint8_t step_pulse_time; // Step pulse reset time after step rise
static uint8_t out_bits; // The next stepping-bits to be output
// NOTE: If the main interrupt is guaranteed to be complete before the next interrupt, then
// this blocking variable is no longer needed. Only here for safety reasons.
static volatile uint8_t busy; // True when "Stepper Driver Interrupt" is being serviced. Used to avoid retriggering that handler.
// __________________________
// /| |\ _________________ ^
// / | | \ /| |\ |
// / | | \ / | | \ s
// / | | | | | \ p
// / | | | | | \ e
// +-----+------------------------+---+--+---------------+----+ e
// | BLOCK 1 | BLOCK 2 | d
//
// time ----->
//
// The trapezoid is the shape the speed curve over time. It starts at block->initial_rate, accelerates by block->rate_delta
// until reaching cruising speed block->nominal_rate, and/or until step_events_remaining reaches block->decelerate_after
// after which it decelerates until the block is completed. The driver uses constant acceleration, which is applied as
// +/- block->rate_delta velocity increments by the midpoint rule at each ACCELERATION_TICKS_PER_SECOND.
// Stepper state initialization. Cycle should only start if the st.cycle_start flag is
// enabled. Startup init and limits call this function but shouldn't start the cycle.
void st_wake_up()
{
// Enable steppers by resetting the stepper disable port
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
}
if (sys.state == STATE_CYCLE) {
// Initialize stepper output bits
out_bits = settings.invert_mask;
// Initialize step pulse timing from settings.
step_pulse_time = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND) >> 3);
// Enable stepper driver interrupt
st.execute_step = false;
TCNT2 = 0; // Clear Timer2
TIMSK2 |= (1<<OCIE2A); // Enable Timer2 Compare Match A interrupt
TCCR2B = (1<<CS21); // Begin Timer2. Full speed, 1/8 prescaler
}
}
// Stepper shutdown
void st_go_idle()
{
// Disable stepper driver interrupt. Allow Timer0 to finish. It will disable itself.
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt
TCCR2B = 0; // Disable Timer2
busy = false;
// Disable steppers only upon system alarm activated or by user setting to not be kept enabled.
if ((settings.stepper_idle_lock_time != 0xff) || bit_istrue(sys.execute,EXEC_ALARM)) {
// Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
// stop and not drift from residual inertial forces at the end of the last movement.
delay_ms(settings.stepper_idle_lock_time);
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
}
}
}
// "The Stepper Driver Interrupt" - This timer interrupt is the workhorse of Grbl. It is based
// on the Pramod Ranade inverse time stepper algorithm, where a timer ticks at a constant
// frequency and uses time-distance counters to track when its the approximate time for any
// step event. However, the Ranade algorithm, as described, is susceptible to numerical round-off,
// meaning that some axes steps may not execute for a given multi-axis motion.
// Grbl's algorithm slightly differs by using a single Ranade time-distance counter to manage
// a Bresenham line algorithm for multi-axis step events which ensures the number of steps for
// each axis are executed exactly. In other words, it uses a Bresenham within a Bresenham algorithm,
// where one tracks time(Ranade) and the other steps.
// This interrupt pops blocks from the block_buffer and executes them by pulsing the stepper pins
// appropriately. It is supported by The Stepper Port Reset Interrupt which it uses to reset the
// stepper port after each pulse. The bresenham line tracer algorithm controls all three stepper
// outputs simultaneously with these two interrupts.
//
// NOTE: Average time in this ISR is: 5 usec iterating timers only, 20-25 usec with step event, or
// 15 usec when popping a block. So, ensure Ranade frequency and step pulse times work with this.
ISR(TIMER2_COMPA_vect)
{
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
if (busy) { return; } // The busy-flag is used to avoid reentering this interrupt
// Pulse stepper port pins, if flagged. New block dir will always be set one timer tick
// before any step pulse due to algorithm design.
if (st.execute_step) {
st.execute_step = false;
STEPPING_PORT = ( STEPPING_PORT & ~(DIRECTION_MASK | STEP_MASK) ) | out_bits;
TCNT0 = step_pulse_time; // Reload Timer0 counter.
TCCR0B = (1<<CS21); // Begin Timer0. Full speed, 1/8 prescaler
}
busy = true;
sei(); // Re-enable interrupts. This ISR will still finish before returning to main program.
// If there is no current block, attempt to pop one from the buffer
if (current_block == NULL) {
// Anything in the buffer? If so, initialize next motion.
current_block = plan_get_current_block();
if (current_block != NULL) {
// By algorithm design, the loading of the next block never coincides with a step event,
// since there is always one Ranade timer tick before a step event occurs. This means
// that the Bresenham counter math never is performed at the same time as the loading
// of a block, hence helping minimize total time spent in this interrupt.
// Initialize direction bits for block
out_bits = current_block->direction_bits ^ settings.invert_mask;
st.execute_step = true; // Set flag to set direction bits.
// Initialize Bresenham variables
st.counter_x = (current_block->step_event_count >> 1);
st.counter_y = st.counter_x;
st.counter_z = st.counter_x;
st.event_count = current_block->step_event_count;
st.step_events_remaining = st.event_count;
// During feed hold, do not update Ranade counter, rate, or ramp type. Keep decelerating.
if (sys.state == STATE_CYCLE) {
// Initialize Ranade variables
st.d_counter = current_block->d_next;
st.delta_d = current_block->initial_rate;
st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK/2;
// Initialize ramp type.
if (st.step_events_remaining == current_block->decelerate_after) { st.ramp_type = DECEL_RAMP; }
else if (st.delta_d == current_block->nominal_rate) { st.ramp_type = CRUISE_RAMP; }
else { st.ramp_type = ACCEL_RAMP; }
}
} else {
st_go_idle();
bit_true(sys.execute,EXEC_CYCLE_STOP); // Flag main program for cycle end
return; // Nothing to do but exit.
}
}
// Adjust inverse time counter for ac/de-celerations
if (st.ramp_type) {
// Tick acceleration ramp counter
st.ramp_count--;
if (st.ramp_count == 0) {
st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK; // Reload ramp counter
if (st.ramp_type == ACCEL_RAMP) { // Adjust velocity for acceleration
st.delta_d += current_block->rate_delta;
if (st.delta_d >= current_block->nominal_rate) { // Reached cruise state.
st.ramp_type = CRUISE_RAMP;
st.delta_d = current_block->nominal_rate; // Set cruise velocity
}
} else if (st.ramp_type == DECEL_RAMP) { // Adjust velocity for deceleration
if (st.delta_d > current_block->rate_delta) {
st.delta_d -= current_block->rate_delta;
} else {
st.delta_d >>= 1; // Integer divide by 2 until complete. Also prevents overflow.
}
}
}
}
// Iterate Pramod Ranade inverse time counter. Triggers each Bresenham step event.
if (st.delta_d < MINIMUM_STEP_RATE) { st.d_counter -= MINIMUM_STEP_RATE; }
else { st.d_counter -= st.delta_d; }
// Execute Bresenham step event, when it's time to do so.
if (st.d_counter < 0) {
st.d_counter += current_block->d_next;
// Check for feed hold state and execute accordingly.
if (sys.state == STATE_HOLD) {
if (st.ramp_type != DECEL_RAMP) {
st.ramp_type = DECEL_RAMP;
st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK/2;
}
if (st.delta_d <= current_block->rate_delta) {
st_go_idle();
bit_true(sys.execute,EXEC_CYCLE_STOP);
return;
}
}
// TODO: Vary Bresenham resolution for smoother motions or enable faster step rates (>20kHz).
out_bits = current_block->direction_bits; // Reset out_bits and reload direction bits
st.execute_step = true;
// Execute step displacement profile by Bresenham line algorithm
st.counter_x -= current_block->steps[X_AXIS];
if (st.counter_x < 0) {
out_bits |= (1<<X_STEP_BIT);
st.counter_x += st.event_count;
if (out_bits & (1<<X_DIRECTION_BIT)) { sys.position[X_AXIS]--; }
else { sys.position[X_AXIS]++; }
}
st.counter_y -= current_block->steps[Y_AXIS];
if (st.counter_y < 0) {
out_bits |= (1<<Y_STEP_BIT);
st.counter_y += st.event_count;
if (out_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS]--; }
else { sys.position[Y_AXIS]++; }
}
st.counter_z -= current_block->steps[Z_AXIS];
if (st.counter_z < 0) {
out_bits |= (1<<Z_STEP_BIT);
st.counter_z += st.event_count;
if (out_bits & (1<<Z_DIRECTION_BIT)) { sys.position[Z_AXIS]--; }
else { sys.position[Z_AXIS]++; }
}
// Check step events for trapezoid change or end of block.
st.step_events_remaining--; // Decrement step events count
if (st.step_events_remaining) {
if (st.ramp_type != DECEL_RAMP) {
// Acceleration and cruise handled by ramping. Just check for deceleration.
if (st.step_events_remaining <= current_block->decelerate_after) {
st.ramp_type = DECEL_RAMP;
if (st.step_events_remaining == current_block->decelerate_after) {
if (st.delta_d == current_block->nominal_rate) {
st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK/2; // Set ramp counter for trapezoid
} else {
st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK-st.ramp_count; // Set ramp counter for triangle
}
}
}
}
} else {
// If current block is finished, reset pointer
current_block = NULL;
plan_discard_current_block();
}
out_bits ^= settings.invert_mask; // Apply step port invert mask
}
busy = false;
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
}
// The Stepper Port Reset Interrupt: Timer0 OVF interrupt handles the falling edge of the
// step pulse. This should always trigger before the next Timer2 COMPA interrupt and independently
// finish, if Timer2 is disabled after completing a move.
ISR(TIMER0_OVF_vect)
{
STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | (settings.invert_mask & STEP_MASK);
TCCR0B = 0; // Disable timer until needed.
}
// Reset and clear stepper subsystem variables
void st_reset()
{
memset(&st, 0, sizeof(st));
current_block = NULL;
busy = false;
}
// Initialize and start the stepper motor subsystem
void st_init()
{
// Configure directions of interface pins
STEPPING_DDR |= STEPPING_MASK;
STEPPING_PORT = (STEPPING_PORT & ~STEPPING_MASK) | settings.invert_mask;
STEPPERS_DISABLE_DDR |= 1<<STEPPERS_DISABLE_BIT;
// Configure Timer 2
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt while configuring it
TCCR2B = 0; // Disable Timer2 until needed
TCNT2 = 0; // Clear Timer2 counter
TCCR2A = (1<<WGM21); // Set CTC mode
OCR2A = (F_CPU/ISR_TICKS_PER_SECOND)/8 - 1; // Set Timer2 CTC rate
// Configure Timer 0
TIMSK0 &= ~(1<<TOIE0);
TCCR0A = 0; // Normal operation
TCCR0B = 0; // Disable Timer0 until needed
TIMSK0 |= (1<<TOIE0); // Enable overflow interrupt
// Start in the idle state, but first wake up to check for keep steppers enabled option.
st_wake_up();
st_go_idle();
}
// Planner external interface to start stepper interrupt and execute the blocks in queue. Called
// by the main program functions: planner auto-start and run-time command execution.
void st_cycle_start()
{
if (sys.state == STATE_QUEUED) {
sys.state = STATE_CYCLE;
st_wake_up();
}
}
// Execute a feed hold with deceleration, only during cycle. Called by main program.
void st_feed_hold()
{
if (sys.state == STATE_CYCLE) {
sys.state = STATE_HOLD;
sys.auto_start = false; // Disable planner auto start upon feed hold.
}
}
// Reinitializes the cycle plan and stepper system after a feed hold for a resume. Called by
// runtime command execution in the main program, ensuring that the planner re-plans safely.
// NOTE: Bresenham algorithm variables are still maintained through both the planner and stepper
// cycle reinitializations. The stepper path should continue exactly as if nothing has happened.
// Only the planner de/ac-celerations profiles and stepper rates have been updated.
void st_cycle_reinitialize()
{
if (current_block != NULL) {
// Replan buffer from the feed hold stop location.
plan_cycle_reinitialize(st.step_events_remaining);
st.ramp_type = ACCEL_RAMP;
st.ramp_count = ISR_TICKS_PER_ACCELERATION_TICK/2;
st.delta_d = 0;
sys.state = STATE_QUEUED;
} else {
sys.state = STATE_IDLE;
}
}

6
config.h
View File

@ -198,6 +198,12 @@
// case, please report any successes to grbl administrators!
// #define ENABLE_XONXOFF // Default disabled. Uncomment to enable.
// Uncomment the following define if you are using hardware that drives high when your limits
// are reached. You will need to ensure that you have appropriate pull-down resistors on the
// limit switch input pins, or that your hardware drives the pins low when they are open (non-
// triggered).
// #define LIMIT_SWITCHES_ACTIVE_HIGH
// ---------------------------------------------------------------------------------------
// TODO: Install compile-time option to send numeric status codes rather than strings.

116
defaults.h
View File

@ -32,13 +32,22 @@
#define DEFAULT_X_STEPS_PER_MM 250.0
#define DEFAULT_Y_STEPS_PER_MM 250.0
#define DEFAULT_Z_STEPS_PER_MM 250.0
#define DEFAULT_X_MAX_RATE 500.0 // mm/min
#define DEFAULT_Y_MAX_RATE 500.0 // mm/min
#define DEFAULT_Z_MAX_RATE 500.0 // mm/min
#define DEFAULT_X_ACCELERATION (10.0*60*60) // 10 mm/min^2
#define DEFAULT_Y_ACCELERATION (10.0*60*60) // 10 mm/min^2
#define DEFAULT_Z_ACCELERATION (10.0*60*60) // 10 mm/min^2
#define DEFAULT_X_MAX_TRAVEL 200.0 // mm
#define DEFAULT_Y_MAX_TRAVEL 200.0 // mm
#define DEFAULT_Z_MAX_TRAVEL 200.0 // mm
#define DEFAULT_STEP_PULSE_MICROSECONDS 10
#define DEFAULT_ARC_TOLERANCE 0.005 // mm
#define DEFAULT_RAPID_FEEDRATE 500.0 // mm/min
#define DEFAULT_FEEDRATE 250.0
#define DEFAULT_ACCELERATION (10.0*60*60) // 10 mm/min^2
#define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
#define DEFAULT_FEEDRATE 250.0 // mm/min
#define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
#define DEFAULT_ARC_TOLERANCE 0.005 // mm
#define DEFAULT_DECIMAL_PLACES 3
#define DEFAULT_REPORT_INCHES 0 // false
#define DEFAULT_AUTO_START 1 // true
#define DEFAULT_INVERT_ST_ENABLE 0 // false
@ -46,15 +55,10 @@
#define DEFAULT_HARD_LIMIT_ENABLE 0 // false
#define DEFAULT_HOMING_ENABLE 0 // false
#define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
#define DEFAULT_HOMING_RAPID_FEEDRATE 250.0 // mm/min
#define DEFAULT_HOMING_FEEDRATE 25.0 // mm/min
#define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
#define DEFAULT_HOMING_SEEK_RATE 250.0 // mm/min
#define DEFAULT_HOMING_DEBOUNCE_DELAY 100 // msec (0-65k)
#define DEFAULT_HOMING_PULLOFF 1.0 // mm
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_DECIMAL_PLACES 3
#define DEFAULT_X_MAX_TRAVEL 200 // mm
#define DEFAULT_Y_MAX_TRAVEL 200 // mm
#define DEFAULT_Z_MAX_TRAVEL 200 // mm
#endif
#ifdef DEFAULTS_SHERLINE_5400
@ -66,29 +70,33 @@
#define DEFAULT_X_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
#define DEFAULT_Y_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
#define DEFAULT_Z_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
#define DEFAULT_X_MAX_RATE 635.0 // mm/min (25 ipm)
#define DEFAULT_Y_MAX_RATE 635.0 // mm/min
#define DEFAULT_Z_MAX_RATE 635.0 // mm/min
#define DEFAULT_X_ACCELERATION (50.0*60*60) // 10 mm/min^2
#define DEFAULT_Y_ACCELERATION (50.0*60*60) // 10 mm/min^2
#define DEFAULT_Z_ACCELERATION (50.0*60*60) // 10 mm/min^2
#define DEFAULT_X_MAX_TRAVEL 200.0 // mm
#define DEFAULT_Y_MAX_TRAVEL 200.0 // mm
#define DEFAULT_Z_MAX_TRAVEL 200.0 // mm
#define DEFAULT_STEP_PULSE_MICROSECONDS 10
#define DEFAULT_ARC_TOLERANCE 0.005 // mm
#define DEFAULT_RAPID_FEEDRATE 635.0 // mm/min (25ipm)
#define DEFAULT_FEEDRATE 254.0 // mm/min (10ipm)
#define DEFAULT_ACCELERATION 50.0*60*60 // 50 mm/min^2
#define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
#define DEFAULT_FEEDRATE 254.0 // mm/min (10 ipm)
#define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
#define DEFAULT_REPORT_INCHES 1 // false
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
#define DEFAULT_ARC_TOLERANCE 0.005 // mm
#define DEFAULT_DECIMAL_PLACES 3
#define DEFAULT_REPORT_INCHES 1 // true
#define DEFAULT_AUTO_START 1 // true
#define DEFAULT_INVERT_ST_ENABLE 0 // false
#define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
#define DEFAULT_HARD_LIMIT_ENABLE 0 // false
#define DEFAULT_HOMING_ENABLE 0 // false
#define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
#define DEFAULT_HOMING_RAPID_FEEDRATE 250.0 // mm/min
#define DEFAULT_HOMING_FEEDRATE 25.0 // mm/min
#define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
#define DEFAULT_HOMING_SEEK_RATE 250.0 // mm/min
#define DEFAULT_HOMING_DEBOUNCE_DELAY 100 // msec (0-65k)
#define DEFAULT_HOMING_PULLOFF 1.0 // mm
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_DECIMAL_PLACES 3
#define DEFAULT_X_MAX_TRAVEL 200 // mm
#define DEFAULT_Y_MAX_TRAVEL 200 // mm
#define DEFAULT_Z_MAX_TRAVEL 200 // mm
#endif
#ifdef DEFAULTS_SHAPEOKO
@ -103,29 +111,33 @@
#define DEFAULT_X_STEPS_PER_MM (MICROSTEPS_XY*STEP_REVS_XY/MM_PER_REV_XY)
#define DEFAULT_Y_STEPS_PER_MM (MICROSTEPS_XY*STEP_REVS_XY/MM_PER_REV_XY)
#define DEFAULT_Z_STEPS_PER_MM (MICROSTEPS_Z*STEP_REVS_Z/MM_PER_REV_Z)
#define DEFAULT_X_MAX_RATE 1000.0 // mm/min
#define DEFAULT_Y_MAX_RATE 1000.0 // mm/min
#define DEFAULT_Z_MAX_RATE 1000.0 // mm/min
#define DEFAULT_X_ACCELERATION (15.0*60*60) // 10 mm/min^2
#define DEFAULT_Y_ACCELERATION (15.0*60*60) // 10 mm/min^2
#define DEFAULT_Z_ACCELERATION (15.0*60*60) // 10 mm/min^2
#define DEFAULT_X_MAX_TRAVEL 200.0 // mm
#define DEFAULT_Y_MAX_TRAVEL 200.0 // mm
#define DEFAULT_Z_MAX_TRAVEL 200.0 // mm
#define DEFAULT_STEP_PULSE_MICROSECONDS 10
#define DEFAULT_ARC_TOLERANCE 0.005 // mm
#define DEFAULT_RAPID_FEEDRATE 1000.0 // mm/min
#define DEFAULT_FEEDRATE 250.0
#define DEFAULT_ACCELERATION (15.0*60*60) // 15 mm/min^2
#define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
#define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 255 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
#define DEFAULT_ARC_TOLERANCE 0.005 // mm
#define DEFAULT_DECIMAL_PLACES 3
#define DEFAULT_REPORT_INCHES 0 // false
#define DEFAULT_AUTO_START 1 // true
#define DEFAULT_INVERT_ST_ENABLE 0 // false
#define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
#define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
#define DEFAULT_HARD_LIMIT_ENABLE 0 // false
#define DEFAULT_HOMING_ENABLE 0 // false
#define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
#define DEFAULT_HOMING_RAPID_FEEDRATE 250.0 // mm/min
#define DEFAULT_HOMING_FEEDRATE 25.0 // mm/min
#define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
#define DEFAULT_HOMING_SEEK_RATE 250.0 // mm/min
#define DEFAULT_HOMING_DEBOUNCE_DELAY 100 // msec (0-65k)
#define DEFAULT_HOMING_PULLOFF 1.0 // mm
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 255 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_DECIMAL_PLACES 3
#define DEFAULT_X_MAX_TRAVEL 200 // mm
#define DEFAULT_Y_MAX_TRAVEL 200 // mm
#define DEFAULT_Z_MAX_TRAVEL 200 // mm
#define DEFAULT_HOMING_PULLOFF 1.0 // mm
#endif
#ifdef DEFAULTS_ZEN_TOOLWORKS_7x7
@ -138,29 +150,33 @@
#define DEFAULT_X_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
#define DEFAULT_Y_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
#define DEFAULT_Z_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
#define DEFAULT_X_MAX_RATE 7000.0 // mm/min
#define DEFAULT_Y_MAX_RATE 7000.0 // mm/min
#define DEFAULT_Z_MAX_RATE 7000.0 // mm/min
#define DEFAULT_X_ACCELERATION (500.0*60*60) // 10 mm/min^2
#define DEFAULT_Y_ACCELERATION (500.0*60*60) // 10 mm/min^2
#define DEFAULT_Z_ACCELERATION (500.0*60*60) // 10 mm/min^2
#define DEFAULT_X_MAX_TRAVEL 200.0 // mm
#define DEFAULT_Y_MAX_TRAVEL 200.0 // mm
#define DEFAULT_Z_MAX_TRAVEL 200.0 // mm
#define DEFAULT_STEP_PULSE_MICROSECONDS 10
#define DEFAULT_ARC_TOLERANCE 0.005 // mm
#define DEFAULT_RAPID_FEEDRATE 4000.0 // mm/min
#define DEFAULT_FEEDRATE 1000.0 // mm/min
#define DEFAULT_ACCELERATION 400.0*60*60 // 150 mm/min^2
#define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
#define DEFAULT_STEPPING_INVERT_MASK (1<<Y_DIRECTION_BIT)
#define DEFAULT_ARC_TOLERANCE 0.005 // mm
#define DEFAULT_DECIMAL_PLACES 3
#define DEFAULT_REPORT_INCHES 0 // false
#define DEFAULT_AUTO_START 1 // true
#define DEFAULT_INVERT_ST_ENABLE 0 // false
#define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
#define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
#define DEFAULT_HARD_LIMIT_ENABLE 0 // false
#define DEFAULT_HOMING_ENABLE 0 // false
#define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
#define DEFAULT_HOMING_RAPID_FEEDRATE 500.0 // mm/min
#define DEFAULT_HOMING_FEEDRATE 50.0 // mm/min
#define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
#define DEFAULT_HOMING_SEEK_RATE 250.0 // mm/min
#define DEFAULT_HOMING_DEBOUNCE_DELAY 100 // msec (0-65k)
#define DEFAULT_HOMING_PULLOFF 1.0 // mm
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_DECIMAL_PLACES 3
#define DEFAULT_X_MAX_TRAVEL 200 // mm
#define DEFAULT_Y_MAX_TRAVEL 200 // mm
#define DEFAULT_Z_MAX_TRAVEL 200 // mm
#endif
#endif

2
gcode.c
View File

@ -140,7 +140,7 @@ uint8_t gc_execute_line(char *line)
case 4: non_modal_action = NON_MODAL_DWELL; break;
case 10: non_modal_action = NON_MODAL_SET_COORDINATE_DATA; break;
case 17: select_plane(X_AXIS, Y_AXIS, Z_AXIS); break;
case 18: select_plane(X_AXIS, Z_AXIS, Y_AXIS); break;
case 18: select_plane(Z_AXIS, X_AXIS, Y_AXIS); break;
case 19: select_plane(Y_AXIS, Z_AXIS, X_AXIS); break;
case 20: gc.inches_mode = true; break;
case 21: gc.inches_mode = false; break;

16
limits.c
View File

@ -35,10 +35,17 @@
#define MICROSECONDS_PER_ACCELERATION_TICK (1000000/ACCELERATION_TICKS_PER_SECOND)
void limits_init()
{
LIMIT_DDR &= ~(LIMIT_MASK); // Set as input pins
LIMIT_PORT |= (LIMIT_MASK); // Enable internal pull-up resistors. Normal high operation.
#ifndef LIMIT_SWITCHES_ACTIVE_HIGH
LIMIT_PORT |= (LIMIT_MASK); // Enable internal pull-up resistors. Normal high operation.
#else // LIMIT_SWITCHES_ACTIVE_HIGH
LIMIT_PORT &= ~(LIMIT_MASK); // Normal low operation. Requires external pull-down.
#endif // !LIMIT_SWITCHES_ACTIVE_HIGH
if (bit_istrue(settings.flags,BITFLAG_HARD_LIMIT_ENABLE)) {
LIMIT_PCMSK |= LIMIT_MASK; // Enable specific pins of the Pin Change Interrupt
PCICR |= (1 << LIMIT_INT); // Enable Pin Change Interrupt
@ -48,6 +55,7 @@ void limits_init()
}
}
// This is the Limit Pin Change Interrupt, which handles the hard limit feature. A bouncing
// limit switch can cause a lot of problems, like false readings and multiple interrupt calls.
// If a switch is triggered at all, something bad has happened and treat it as such, regardless
@ -94,7 +102,11 @@ static void homing_cycle(uint8_t cycle_mask, int8_t pos_dir, bool invert_pin, fl
This will also fix the slow max feedrate of the homing 'lite' stepper algorithm.
Need to check if setting the planner steps will require them to be volatile or not. */
#ifdef LIMIT_SWITCHES_ACTIVE_HIGH
// When in an active-high switch configuration, invert_pin needs to be adjusted.
invert_pin = !invert_pin;
#endif
// Determine governing axes with finest step resolution per distance for the Bresenham
// algorithm. This solves the issue when homing multiple axes that have different

14
planner.c
View File

@ -35,10 +35,10 @@
// to be larger than any feasible (mm/min)^2 or mm/sec^2 value.
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
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 {
@ -127,7 +127,7 @@ static uint8_t plan_prev_block_index(uint8_t block_index)
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
segment(s) distance per block to a desired tolerance. The more combined distance the planner has to use,
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
@ -329,7 +329,7 @@ void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate)
inverse_unit_vec_value = abs(1.0/unit_vec[idx]); // Inverse to remove multiple float divides.
// Check and limit feed rate against max individual axis velocities and accelerations
feed_rate = min(feed_rate,settings.max_velocity[idx]*inverse_unit_vec_value);
feed_rate = min(feed_rate,settings.max_rate[idx]*inverse_unit_vec_value);
block->acceleration = min(block->acceleration,settings.acceleration[idx]*inverse_unit_vec_value);
// Incrementally compute cosine of angle between previous and current path. Cos(theta) of the junction
@ -417,7 +417,7 @@ void plan_sync_position()
void plan_cycle_reinitialize()
{
// Re-plan from a complete stop. Reset planner entry speeds and buffer planned pointer.
// st_update_plan_block_parameters();
st_update_plan_block_parameters();
block_buffer_planned = block_buffer_tail;
planner_recalculate();
}

29
planner.h
View File

@ -28,25 +28,24 @@
#define BLOCK_BUFFER_SIZE 18
#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.
// This struct stores a linear movement of a g-code block motion with its critical "nominal" values
// are as specified in the source g-code.
typedef struct {
// Fields used by the bresenham algorithm for tracing the line
// NOTE: Do not change any of these values once set. The stepper algorithm uses them to execute the block correctly.
uint8_t direction_bits; // The direction bit set for this block (refers to *_DIRECTION_BIT in config.h)
int32_t steps[N_AXIS]; // Step count along each axis
int32_t step_event_count; // The maximum step axis count and number of steps required to complete this block.
// NOTE: Used by stepper algorithm to execute the block correctly. Do not alter these values.
uint8_t direction_bits; // The direction bit set for this block (refers to *_DIRECTION_BIT in config.h)
int32_t steps[N_AXIS]; // Step count along each axis
int32_t step_event_count; // The maximum step axis count and number of steps required to complete this block.
// Fields used by the motion planner to manage acceleration
float entry_speed_sqr; // The current planned entry speed at block junction in (mm/min)^2
float max_entry_speed_sqr; // Maximum allowable entry speed based on the minimum of junction limit and
// neighboring nominal speeds with overrides in (mm/min)^2
float max_junction_speed_sqr; // Junction entry speed limit based on direction vectors in (mm/min)^2
float nominal_speed_sqr; // Axis-limit adjusted nominal speed for this block in (mm/min)^2
float acceleration; // Axis-limit adjusted line acceleration in (mm/min^2)
float millimeters; // The remaining distance for this block to be executed in (mm)
// uint8_t max_override; // Maximum override value based on axis speed limits
float entry_speed_sqr; // The current planned entry speed at block junction in (mm/min)^2
float max_entry_speed_sqr; // Maximum allowable entry speed based on the minimum of junction limit and
// neighboring nominal speeds with overrides in (mm/min)^2
float max_junction_speed_sqr; // Junction entry speed limit based on direction vectors in (mm/min)^2
float nominal_speed_sqr; // Axis-limit adjusted nominal speed for this block in (mm/min)^2
float acceleration; // Axis-limit adjusted line acceleration in (mm/min^2)
float millimeters; // The remaining distance for this block to be executed in (mm)
// uint8_t max_override; // Maximum override value based on axis speed limits
} plan_block_t;

8
report.c
View File

@ -151,10 +151,10 @@ void report_grbl_settings() {
printPgmString(PSTR("$0=")); printFloat(settings.steps_per_mm[X_AXIS]);
printPgmString(PSTR(" (x, step/mm)\r\n$1=")); printFloat(settings.steps_per_mm[Y_AXIS]);
printPgmString(PSTR(" (y, step/mm)\r\n$2=")); printFloat(settings.steps_per_mm[Z_AXIS]);
printPgmString(PSTR(" (z, step/mm)\r\n$3=")); printFloat(settings.max_velocity[X_AXIS]);
printPgmString(PSTR(" (x v_max, mm/min)\r\n$4=")); printFloat(settings.max_velocity[Y_AXIS]);
printPgmString(PSTR(" (y v_max, mm/min)\r\n$5=")); printFloat(settings.max_velocity[Z_AXIS]);
printPgmString(PSTR(" (z v_max, mm/min)\r\n$6=")); printFloat(settings.acceleration[X_AXIS]/(60*60)); // Convert from mm/min^2 for human readability
printPgmString(PSTR(" (z, step/mm)\r\n$3=")); printFloat(settings.max_rate[X_AXIS]);
printPgmString(PSTR(" (x max rate, mm/min)\r\n$4=")); printFloat(settings.max_rate[Y_AXIS]);
printPgmString(PSTR(" (y max rate, mm/min)\r\n$5=")); printFloat(settings.max_rate[Z_AXIS]);
printPgmString(PSTR(" (z max rate, mm/min)\r\n$6=")); printFloat(settings.acceleration[X_AXIS]/(60*60)); // Convert from mm/min^2 for human readability
printPgmString(PSTR(" (x accel, mm/sec^2)\r\n$7=")); printFloat(settings.acceleration[Y_AXIS]/(60*60)); // Convert from mm/min^2 for human readability
printPgmString(PSTR(" (y accel, mm/sec^2)\r\n$8=")); printFloat(settings.acceleration[Z_AXIS]/(60*60)); // Convert from mm/min^2 for human readability
printPgmString(PSTR(" (z accel, mm/sec^2)\r\n$9=")); printFloat(-settings.max_travel[X_AXIS]); // Grbl internally store this as negative.

16
serial.c
View File

@ -30,7 +30,7 @@
uint8_t rx_buffer[RX_BUFFER_SIZE];
uint8_t rx_buffer_head = 0;
uint8_t rx_buffer_tail = 0;
volatile uint8_t rx_buffer_tail = 0;
uint8_t tx_buffer[TX_BUFFER_SIZE];
uint8_t tx_buffer_head = 0;
@ -93,8 +93,7 @@ void serial_write(uint8_t data) {
// Data Register Empty Interrupt handler
ISR(SERIAL_UDRE)
{
// Temporary tx_buffer_tail (to optimize for volatile)
uint8_t tail = tx_buffer_tail;
uint8_t tail = tx_buffer_tail; // Temporary tx_buffer_tail (to optimize for volatile)
#ifdef ENABLE_XONXOFF
if (flow_ctrl == SEND_XOFF) {
@ -122,12 +121,15 @@ ISR(SERIAL_UDRE)
uint8_t serial_read()
{
if (rx_buffer_head == rx_buffer_tail) {
uint8_t tail = rx_buffer_tail; // Temporary rx_buffer_tail (to optimize for volatile)
if (rx_buffer_head == tail) {
return SERIAL_NO_DATA;
} else {
uint8_t data = rx_buffer[rx_buffer_tail];
rx_buffer_tail++;
if (rx_buffer_tail == RX_BUFFER_SIZE) { rx_buffer_tail = 0; }
uint8_t data = rx_buffer[tail];
tail++;
if (tail == RX_BUFFER_SIZE) { tail = 0; }
rx_buffer_tail = tail;
#ifdef ENABLE_XONXOFF
if ((get_rx_buffer_count() < RX_BUFFER_LOW) && flow_ctrl == XOFF_SENT) {

22
settings.c
View File

@ -73,12 +73,12 @@ void settings_reset(bool reset_all) {
settings.steps_per_mm[Z_AXIS] = DEFAULT_Z_STEPS_PER_MM;
settings.pulse_microseconds = DEFAULT_STEP_PULSE_MICROSECONDS;
settings.default_feed_rate = DEFAULT_FEEDRATE;
settings.max_velocity[X_AXIS] = DEFAULT_RAPID_FEEDRATE;
settings.max_velocity[Y_AXIS] = DEFAULT_RAPID_FEEDRATE;
settings.max_velocity[Z_AXIS] = DEFAULT_RAPID_FEEDRATE;
settings.acceleration[X_AXIS] = DEFAULT_ACCELERATION;
settings.acceleration[Y_AXIS] = DEFAULT_ACCELERATION;
settings.acceleration[Z_AXIS] = DEFAULT_ACCELERATION;
settings.max_rate[X_AXIS] = DEFAULT_X_MAX_RATE;
settings.max_rate[Y_AXIS] = DEFAULT_Y_MAX_RATE;
settings.max_rate[Z_AXIS] = DEFAULT_Z_MAX_RATE;
settings.acceleration[X_AXIS] = DEFAULT_X_ACCELERATION;
settings.acceleration[Y_AXIS] = DEFAULT_Y_ACCELERATION;
settings.acceleration[Z_AXIS] = DEFAULT_Z_ACCELERATION;
settings.arc_tolerance = DEFAULT_ARC_TOLERANCE;
settings.invert_mask = DEFAULT_STEPPING_INVERT_MASK;
settings.junction_deviation = DEFAULT_JUNCTION_DEVIATION;
@ -92,8 +92,8 @@ void settings_reset(bool reset_all) {
if (DEFAULT_HARD_LIMIT_ENABLE) { settings.flags |= BITFLAG_HARD_LIMIT_ENABLE; }
if (DEFAULT_HOMING_ENABLE) { settings.flags |= BITFLAG_HOMING_ENABLE; }
settings.homing_dir_mask = DEFAULT_HOMING_DIR_MASK;
settings.homing_feed_rate = DEFAULT_HOMING_FEEDRATE;
settings.homing_seek_rate = DEFAULT_HOMING_RAPID_FEEDRATE;
settings.homing_feed_rate = DEFAULT_HOMING_FEED_RATE;
settings.homing_seek_rate = DEFAULT_HOMING_SEEK_RATE;
settings.homing_debounce_delay = DEFAULT_HOMING_DEBOUNCE_DELAY;
settings.homing_pulloff = DEFAULT_HOMING_PULLOFF;
settings.stepper_idle_lock_time = DEFAULT_STEPPER_IDLE_LOCK_TIME;
@ -163,9 +163,9 @@ uint8_t settings_store_global_setting(int parameter, float value) {
case 0: case 1: case 2:
if (value <= 0.0) { return(STATUS_SETTING_VALUE_NEG); }
settings.steps_per_mm[parameter] = value; break;
case 3: settings.max_velocity[X_AXIS] = value; break;
case 4: settings.max_velocity[Y_AXIS] = value; break;
case 5: settings.max_velocity[Z_AXIS] = value; break;
case 3: settings.max_rate[X_AXIS] = value; break;
case 4: settings.max_rate[Y_AXIS] = value; break;
case 5: settings.max_rate[Z_AXIS] = value; break;
case 6: settings.acceleration[X_AXIS] = value*60*60; break; // Convert to mm/min^2 for grbl internal use.
case 7: settings.acceleration[Y_AXIS] = value*60*60; break; // Convert to mm/min^2 for grbl internal use.
case 8: settings.acceleration[Z_AXIS] = value*60*60; break; // Convert to mm/min^2 for grbl internal use.

18
settings.h
View File

@ -25,11 +25,11 @@
#include <math.h>
#include "nuts_bolts.h"
#define GRBL_VERSION "0.9a"
#define GRBL_VERSION "0.9b"
// Version of the EEPROM data. Will be used to migrate existing data from older versions of Grbl
// when firmware is upgraded. Always stored in byte 0 of eeprom
#define SETTINGS_VERSION 53
#define SETTINGS_VERSION 55
// Define bit flag masks for the boolean settings in settings.flag.
#define BITFLAG_REPORT_INCHES bit(0)
@ -58,24 +58,22 @@
// Global persistent settings (Stored from byte EEPROM_ADDR_GLOBAL onwards)
typedef struct {
float steps_per_mm[N_AXIS];
uint8_t microsteps;
float max_rate[N_AXIS];
float acceleration[N_AXIS];
float max_travel[N_AXIS];
uint8_t pulse_microseconds;
float default_feed_rate;
float default_seek_rate;
uint8_t invert_mask;
float arc_tolerance;
float acceleration[N_AXIS];
uint8_t stepper_idle_lock_time; // If max value 255, steppers do not disable.
float junction_deviation;
float arc_tolerance;
uint8_t decimal_places;
uint8_t flags; // Contains default boolean settings
uint8_t homing_dir_mask;
float homing_feed_rate;
float homing_seek_rate;
uint16_t homing_debounce_delay;
float homing_pulloff;
uint8_t stepper_idle_lock_time; // If max value 255, steppers do not disable.
uint8_t decimal_places;
float max_velocity[N_AXIS];
float max_travel[N_AXIS];
// uint8_t status_report_mask; // Mask to indicate desired report data.
} settings_t;
extern settings_t settings;

152
stepper.c
View File

@ -105,10 +105,9 @@ typedef struct {
float step_per_mm; // Current planner block step/millimeter conversion scalar
float steps_remaining;
int32_t step_events_remaining; // Tracks step event count for the executing planner block
uint8_t ramp_type; // Current segment ramp state
float millimeters_remaining;
float mm_eob;
float current_speed; // Current speed at the end of the segment buffer (mm/min)
float maximum_speed; // Maximum speed of executing block. Not always nominal speed. (mm/min)
float exit_speed; // Exit speed of executing block (mm/min)
@ -217,15 +216,14 @@ void st_go_idle()
stepper pins appropriately. It is supported by The Stepper Port Reset Interrupt which it uses
to reset the stepper port after each pulse. The bresenham line tracer algorithm controls all
three stepper outputs simultaneously with these two interrupts.
NOTE: This interrupt must be as efficient as possible and complete before the next ISR tick,
which for Grbl is 33.3usec at a 30kHz ISR rate. Oscilloscope measured time in ISR is 5usec
typical and 25usec maximum, well below requirement.
*/
/* TODO:
- Measured time in ISR. Typical and worst-case. Roughly 5usec min to 25usec max. Good enough.
There are no major changes to the base operations of this ISR with the new segment buffer.
- Determine if placing the position counters elsewhere (or change them to 8-bit variables that
are added to the system position counters at the end of a segment) frees up cycles.
- Create NOTE: to describe that the total time in this ISR must be less than the ISR frequency
in its worst case scenario.
*/
// TODO: Replace direct updating of the int32 position counters in the ISR somehow. Perhaps use smaller
// int8 variables and update position counters only when a segment completes. This can get complicated
// with probing and homing cycles that require true real-time positions.
ISR(TIMER2_COMPA_vect)
{
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
@ -424,7 +422,6 @@ void st_update_plan_block_parameters()
{
if (pl_block != NULL) { // Ignore if at start of a new block.
prep.flag_partial_block = true;
pl_block->millimeters = prep.millimeters_remaining;
pl_block->entry_speed_sqr = prep.current_speed*prep.current_speed; // Update entry speed.
pl_block = NULL; // Flag st_prep_segment() to load new velocity profile.
}
@ -456,32 +453,12 @@ void st_update_plan_block_parameters()
accounted for. This allows the stepper algorithm to run at very high step rates without
losing steps.
*/
/*
TODO: With feedrate overrides, increases to the override value will not significantly
change the planner and stepper current operation. When the value increases, we simply
need to recompute the block plan with new nominal speeds and maximum junction velocities.
However with a decreasing feedrate override, this gets a little tricky. The current block
plan is optimal, so if we try to reduce the feed rates, it may be impossible to create
a feasible plan at its current operating speed and decelerate down to zero at the end of
the buffer. We first have to enforce a deceleration to meet and intersect with the reduced
feedrate override plan. For example, if the current block is cruising at a nominal rate
and the feedrate override is reduced, the new nominal rate will now be lower. The velocity
profile must first decelerate to the new nominal rate and then follow on the new plan.
Another issue is whether or not a feedrate override reduction causes a deceleration
that acts over several planner blocks. For example, say that the plan is already heavily
decelerating throughout it, reducing the feedrate override will not do much to it. So,
how do we determine when to resume the new plan? One solution is to tie into the feed hold
handling code to enforce a deceleration, but check when the current speed is less than or
equal to the block maximum speed and is in an acceleration or cruising ramp. At this
point, we know that we can recompute the block velocity profile to meet and continue onto
the new block plan.
*/
void st_prep_buffer()
{
while (segment_buffer_tail != segment_next_head) { // Check if we need to fill the buffer.
if (sys.state == STATE_QUEUED) { return; } // Block until a motion state is issued
// Determine if we need to load a new planner block. If so, prepare step data.
// Determine if we need to load a new planner block or if the block remainder is replanned.
if (pl_block == NULL) {
pl_block = plan_get_current_block(); // Query planner for a queued block
if (pl_block == NULL) { return; } // No planner blocks. Exit.
@ -504,10 +481,8 @@ void st_prep_buffer()
st_prep_block->step_event_count = pl_block->step_event_count;
// Initialize segment buffer data for generating the segments.
prep.step_events_remaining = st_prep_block->step_event_count;
prep.steps_remaining = st_prep_block->step_event_count;
prep.millimeters_remaining = pl_block->millimeters;
prep.step_per_mm = prep.steps_remaining/prep.millimeters_remaining;
prep.step_per_mm = prep.steps_remaining/pl_block->millimeters;
if (sys.state == STATE_HOLD) {
prep.current_speed = prep.exit_speed;
@ -516,28 +491,30 @@ void st_prep_buffer()
else { prep.current_speed = sqrt(pl_block->entry_speed_sqr); }
}
prep.mm_eob = 0.0;
float inv_2_accel = 0.5/pl_block->acceleration;
if (sys.state == STATE_HOLD) {
// Compute velocity profile parameters for a feed hold in-progress.
// Compute velocity profile parameters for a feed hold in-progress. This profile overrides
// the planner block profile, enforcing a deceleration to zero speed.
prep.ramp_type = RAMP_DECEL;
float decel_dist = inv_2_accel*pl_block->entry_speed_sqr;
if (decel_dist < prep.millimeters_remaining) {
if (decel_dist < pl_block->millimeters) {
prep.exit_speed = 0.0;
prep.steps_remaining = prep.step_per_mm*decel_dist;
prep.millimeters_remaining = decel_dist;
prep.mm_eob = pl_block->millimeters-decel_dist;
} else {
prep.exit_speed = sqrt(pl_block->entry_speed_sqr-2*pl_block->acceleration*prep.millimeters_remaining);
prep.exit_speed = sqrt(pl_block->entry_speed_sqr-2*pl_block->acceleration*pl_block->millimeters);
}
} else {
// Compute velocity profile parameters of the prepped planner block.
prep.ramp_type = RAMP_ACCEL; // Initialize as acceleration ramp.
prep.accelerate_until = prep.millimeters_remaining;
prep.accelerate_until = pl_block->millimeters;
prep.exit_speed = plan_get_exec_block_exit_speed();
float exit_speed_sqr = prep.exit_speed*prep.exit_speed;
float intersect_distance =
0.5*(prep.millimeters_remaining+inv_2_accel*(pl_block->entry_speed_sqr-exit_speed_sqr));
0.5*(pl_block->millimeters+inv_2_accel*(pl_block->entry_speed_sqr-exit_speed_sqr));
if (intersect_distance > 0.0) {
if (intersect_distance < prep.millimeters_remaining) { // Either trapezoid or triangle types
if (intersect_distance < pl_block->millimeters) { // Either trapezoid or triangle types
// NOTE: For acceleration-cruise and cruise-only types, following calculation will be 0.0.
prep.decelerate_after = inv_2_accel*(pl_block->nominal_speed_sqr-exit_speed_sqr);
if (prep.decelerate_after < intersect_distance) { // Trapezoid type
@ -556,16 +533,15 @@ void st_prep_buffer()
}
} else { // Deceleration-only type
prep.ramp_type = RAMP_DECEL;
prep.decelerate_after = prep.millimeters_remaining;
// prep.decelerate_after = pl_block->millimeters;
prep.maximum_speed = prep.current_speed;
}
} else { // Acceleration-only type
prep.accelerate_until = 0.0;
prep.decelerate_after = 0.0;
// prep.decelerate_after = 0.0;
prep.maximum_speed = prep.exit_speed;
}
}
}
}
// Initialize new segment
@ -584,18 +560,18 @@ void st_prep_buffer()
considered completed despite having a truncated execution time less than DT_SEGMENT.
*/
float dt = 0.0;
float mm_remaining = prep.millimeters_remaining;
float mm_remaining = pl_block->millimeters;
float time_var = DT_SEGMENT; // Time worker variable
float mm_var; // mm distance worker variable
do {
switch (prep.ramp_type) {
case RAMP_ACCEL:
// NOTE: Acceleration ramp always computes during first loop only.
// NOTE: Acceleration ramp only computes during first do-while loop.
mm_remaining -= DT_SEGMENT*(prep.current_speed + pl_block->acceleration*(0.5*DT_SEGMENT));
if (mm_remaining < prep.accelerate_until) { // End of acceleration ramp.
// Acceleration-cruise, acceleration-deceleration ramp junction, or end of block.
mm_remaining = prep.accelerate_until; // NOTE: 0.0 at EOB
time_var = 2.0*(prep.millimeters_remaining-mm_remaining)/(prep.current_speed+prep.maximum_speed);
time_var = 2.0*(pl_block->millimeters-mm_remaining)/(prep.current_speed+prep.maximum_speed);
if (mm_remaining == prep.decelerate_after) { prep.ramp_type = RAMP_DECEL; }
else { prep.ramp_type = RAMP_CRUISE; }
prep.current_speed = prep.maximum_speed;
@ -618,21 +594,21 @@ void st_prep_buffer()
default: // case RAMP_DECEL:
// NOTE: mm_var used to catch negative decelerate distance values near zero speed.
mm_var = time_var*(prep.current_speed - 0.5*pl_block->acceleration*time_var);
if ((mm_var > 0.0) && (mm_var < mm_remaining)) { // Deceleration only.
if ((mm_var > prep.mm_eob) && (mm_var < mm_remaining)) { // Deceleration only.
prep.current_speed -= pl_block->acceleration*time_var;
// Check for near-zero speed and prevent divide by zero in rare scenarios.
if (prep.current_speed > prep.exit_speed) { mm_remaining -= mm_var; }
else { mm_remaining = 0.0; } // NOTE: Force EOB for now. May or may not be needed.
else { mm_remaining = prep.mm_eob; } // NOTE: Force EOB for now. May or may not be needed.
} else { // End of block.
time_var = 2.0*mm_remaining/(prep.current_speed+prep.exit_speed);
mm_remaining = 0.0;
time_var = 2.0*(mm_remaining-prep.mm_eob)/(prep.current_speed+prep.exit_speed);
mm_remaining = prep.mm_eob;
// prep.current_speed = prep.exit_speed; // !! May be needed for feed hold reinitialization.
}
}
dt += time_var; // Add computed ramp time to total segment time.
if (dt < DT_SEGMENT) { time_var = DT_SEGMENT - dt; } // **Incomplete** At ramp junction.
else { break; } // **Complete** Exit loop. Segment execution time maxed.
} while ( mm_remaining > 0.0 ); // **Complete** Exit loop. End of planner block.
} while (mm_remaining > prep.mm_eob); // **Complete** Exit loop. End of planner block.
/* -----------------------------------------------------------------------------------
Compute segment step rate, steps to execute, and step phase correction parameters.
@ -654,38 +630,37 @@ void st_prep_buffer()
prep_segment->phase_dist = ceil(INV_TIME_MULTIPLIER*(ceil(steps_remaining)-steps_remaining));
prep_segment->n_step = ceil(prep.steps_remaining)-ceil(steps_remaining);
// Update step execution variables
prep.step_events_remaining -= prep_segment->n_step;
prep.millimeters_remaining = mm_remaining;
prep.steps_remaining = steps_remaining;
// Update step execution variables.
if (mm_remaining == prep.mm_eob) {
// NOTE: Currently only feed holds qualify for this scenario. May change with overrides.
prep.current_speed = 0.0;
prep.steps_remaining = ceil(steps_remaining);
pl_block->millimeters = prep.steps_remaining/prep.step_per_mm;
plan_cycle_reinitialize();
sys.state = STATE_QUEUED; // End cycle.
} else {
pl_block->millimeters = mm_remaining;
prep.steps_remaining = steps_remaining;
}
} else { // End of block.
// Set to execute the remaining steps and no phase correction upon finishing the block.
prep_segment->dist_per_tick = ceil( prep.steps_remaining*time_var ); // (mult*step/isr_tic)
prep_segment->phase_dist = 0;
prep_segment->n_step = ceil(prep.steps_remaining);
// The planner block is complete. All steps are set to be executed in the segment buffer.
// TODO: Broken with feed holds. Need to recalculate the planner buffer at this time.
pl_block = NULL;
plan_discard_current_block();
prep.step_events_remaining -= prep_segment->n_step;
if (prep.step_events_remaining > 0) {
sys.state = STATE_QUEUED;
pl_block->entry_speed_sqr = 0.0;
prep.current_speed = 0.0;
prep.steps_remaining = prep.step_events_remaining;
pl_block->millimeters = prep.steps_remaining/prep.step_per_mm;
prep.millimeters_remaining = pl_block->millimeters;
pl_block = NULL;
prep.flag_partial_block = true;
plan_cycle_reinitialize();
} else {
// The planner block is complete. All steps are set to be executed in the segment buffer.
// TODO: Ignore this for feed holds. Need to recalculate the planner buffer at this time.
pl_block = NULL;
plan_discard_current_block();
if (sys.state == STATE_HOLD) {
if (prep.current_speed == 0.0) {
plan_cycle_reinitialize();
sys.state = STATE_QUEUED;
}
}
}
// New step segment initialization completed. Increment segment buffer indices.
segment_buffer_head = segment_next_head;
@ -696,3 +671,24 @@ void st_prep_buffer()
// printInteger(blength);
}
}
/*
TODO: With feedrate overrides, increases to the override value will not significantly
change the planner and stepper current operation. When the value increases, we simply
need to recompute the block plan with new nominal speeds and maximum junction velocities.
However with a decreasing feedrate override, this gets a little tricky. The current block
plan is optimal, so if we try to reduce the feed rates, it may be impossible to create
a feasible plan at its current operating speed and decelerate down to zero at the end of
the buffer. We first have to enforce a deceleration to meet and intersect with the reduced
feedrate override plan. For example, if the current block is cruising at a nominal rate
and the feedrate override is reduced, the new nominal rate will now be lower. The velocity
profile must first decelerate to the new nominal rate and then follow on the new plan.
Another issue is whether or not a feedrate override reduction causes a deceleration
that acts over several planner blocks. For example, say that the plan is already heavily
decelerating throughout it, reducing the feedrate override will not do much to it. So,
how do we determine when to resume the new plan? One solution is to tie into the feed hold
handling code to enforce a deceleration, but check when the current speed is less than or
equal to the block maximum speed and is in an acceleration or cruising ramp. At this
point, we know that we can recompute the block velocity profile to meet and continue onto
the new block plan.
*/

788
stepper_test.c
View File

@ -1,788 +0,0 @@
/*
stepper.c - stepper motor driver: executes motion plans using stepper motors
Part of Grbl
Copyright (c) 2011-2013 Sungeun K. Jeon
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/>.
*/
#include <avr/interrupt.h>
#include "stepper.h"
#include "config.h"
#include "settings.h"
#include "planner.h"
#include "nuts_bolts.h"
// Some useful constants
#define TICKS_PER_MICROSECOND (F_CPU/1000000)
#define RAMP_NOOP_CRUISE 0
#define RAMP_ACCEL 1
#define RAMP_DECEL 2
#define LOAD_NOOP 0
#define LOAD_SEGMENT 1
#define LOAD_BLOCK 2
#define SEGMENT_NOOP 0
#define SEGMENT_END_OF_BLOCK bit(0)
#define RAMP_CHANGE_ACCEL bit(1)
#define RAMP_CHANGE_DECEL bit(2)
#define MINIMUM_STEPS_PER_SEGMENT 1 // Don't change
#define SEGMENT_BUFFER_SIZE 6
#define DT_SEGMENT (1/ACCELERATION_TICKS_PER_SECOND)
// Stepper state variable. Contains running data and trapezoid variables.
typedef struct {
// Used by the bresenham line algorithm
int32_t counter_x, // Counter variables for the bresenham line tracer
counter_y,
counter_z;
// Used by inverse time algorithm to track step rate
int32_t counter_dist; // Inverse time distance traveled since last step event
uint8_t step_count; // Steps remaining in line segment motion
uint8_t phase_count; // Phase ticks remaining after line segment steps complete
// Used by the stepper driver interrupt
uint8_t execute_step; // Flags step execution for each interrupt.
uint8_t step_pulse_time; // Step pulse reset time after step rise
uint8_t out_bits; // The next stepping-bits to be output
uint8_t load_flag;
} stepper_t;
static stepper_t st;
// Stores stepper common data for executing steps in the segment buffer. Data can change mid-block when the
// planner updates the remaining block velocity profile with a more optimal plan or a feedrate override occurs.
// NOTE: Normally, this buffer is partially in-use, but, for the worst case scenario, it will never exceed
// the number of accessible stepper buffer segments (SEGMENT_BUFFER_SIZE-1).
typedef struct {
// TODO: Retain step[N_AXIS], step_event_count, and direction byte here, so that we can throw
// away the planner block when the segment prep is complete.
float step_events_remaining; // Tracks step event count for the executing planner block
// Planner block velocity profile parameters used to trace and execute steps.;
float accelerate_until;
float decelerate_after;
float current_speed;
float maximum_speed;
float exit_speed;
} st_data_t;
static st_data_t segment_data[SEGMENT_BUFFER_SIZE-1];
// Primary stepper segment ring buffer. Contains small, short line segments for the stepper algorithm to execute,
// which are "checked-out" incrementally from the first block in the planner buffer. Once "checked-out", the steps
// in the segments buffer cannot be modified by the planner, where the remaining planner block steps still can.
typedef struct {
uint8_t n_step; // Number of step events to be executed for this segment
uint8_t n_phase_tick;
uint32_t dist_per_tick;
uint8_t st_data_index; // Stepper buffer common data index. Uses this information to execute this segment.
uint8_t flag; // Stepper algorithm bit-flag for special execution conditions.
} st_segment_t;
static st_segment_t segment_buffer[SEGMENT_BUFFER_SIZE];
// Step segment ring buffer indices
static volatile uint8_t segment_buffer_tail;
static volatile uint8_t segment_buffer_head;
static uint8_t segment_next_head;
static volatile uint8_t busy; // Used to avoid ISR nesting of the "Stepper Driver Interrupt". Should never occur though.
static plan_block_t *pl_current_block; // A pointer to the planner block currently being traced
static st_segment_t *st_current_segment;
static st_data_t *st_current_data;
// Pointers for the step segment being prepped from the planner buffer. Accessed only by the
// main program. Pointers may be planning segments or planner blocks ahead of what being executed.
static plan_block_t *pl_prep_block; // Pointer to the planner block being prepped
static st_data_t *st_prep_data; // Pointer to the stepper common data being prepped
static uint8_t pl_prep_index; // Index of planner block being prepped
static uint8_t st_data_prep_index; // Index of stepper common data block being prepped
static uint8_t pl_partial_block_flag; // Flag indicating the planner has modified the prepped planner block
static float st_prep_step_per_mm;
// TODO: All this stuff only needs to be retained for the prepped planner block. Once changed
// or complete, we do not need this information anymore. Duh!
// typedef struct {
// float step_events_remaining; // Tracks step event count for the executing planner block
// float accelerate_until;
// float decelerate_after;
// float current_speed;
// float maximum_speed;
// float exit_speed;
// float step_per_mm;
// } st_prep_data_t;
/* __________________________
/| |\ _________________ ^
/ | | \ /| |\ |
/ | | \ / | | \ s
/ | | | | | \ p
/ | | | | | \ e
+-----+------------------------+---+--+---------------+----+ e
| BLOCK 1 | BLOCK 2 | d
time ----->
The trapezoid is the shape the speed curve over time. It starts at block->initial_rate, accelerates by block->rate_delta
until reaching cruising speed block->nominal_rate, and/or until step_events_remaining reaches block->decelerate_after
after which it decelerates until the block is completed. The driver uses constant acceleration, which is applied as
+/- block->rate_delta velocity increments by the midpoint rule at each ACCELERATION_TICKS_PER_SECOND.
*/
// Stepper state initialization. Cycle should only start if the st.cycle_start flag is
// enabled. Startup init and limits call this function but shouldn't start the cycle.
void st_wake_up()
{
// Enable steppers by resetting the stepper disable port
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
}
if (sys.state == STATE_CYCLE) {
// Initialize stepper output bits
st.out_bits = settings.invert_mask;
// Initialize step pulse timing from settings.
st.step_pulse_time = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND) >> 3);
// Enable stepper driver interrupt
st.execute_step = false;
st.load_flag = LOAD_BLOCK;
TCNT2 = 0; // Clear Timer2
TIMSK2 |= (1<<OCIE2A); // Enable Timer2 Compare Match A interrupt
TCCR2B = (1<<CS21); // Begin Timer2. Full speed, 1/8 prescaler
}
}
// Stepper shutdown
void st_go_idle()
{
// Disable stepper driver interrupt. Allow Timer0 to finish. It will disable itself.
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt
TCCR2B = 0; // Disable Timer2
busy = false;
// Disable steppers only upon system alarm activated or by user setting to not be kept enabled.
if ((settings.stepper_idle_lock_time != 0xff) || bit_istrue(sys.execute,EXEC_ALARM)) {
// Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
// stop and not drift from residual inertial forces at the end of the last movement.
delay_ms(settings.stepper_idle_lock_time);
if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) {
STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
} else {
STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
}
}
}
/* "The Stepper Driver Interrupt" - This timer interrupt is the workhorse of Grbl. It is based
on an inverse time stepper algorithm, where a timer ticks at a constant frequency and uses
time-distance counters to track when its the approximate time for a step event. For reference,
a similar inverse-time algorithm by Pramod Ranade is susceptible to numerical round-off, as
described, meaning that some axes steps may not execute correctly for a given multi-axis motion.
Grbl's algorithm differs by using a single inverse time-distance counter to manage a
Bresenham line algorithm for multi-axis step events, which ensures the number of steps for
each axis are executed exactly. In other words, Grbl uses a Bresenham within a Bresenham
algorithm, where one tracks time for step events and the other steps for multi-axis moves.
Grbl specifically uses the Bresenham algorithm due to its innate mathematical exactness and
low computational overhead, requiring simple integer +,- counters only.
This interrupt pops blocks from the step segment buffer and executes them by pulsing the
stepper pins appropriately. It is supported by The Stepper Port Reset Interrupt which it uses
to reset the stepper port after each pulse. The bresenham line tracer algorithm controls all
three stepper outputs simultaneously with these two interrupts.
*/
/* TODO:
- Measure time in ISR. Typical and worst-case. Should be virtually identical to last algorithm.
There are no major changes to the base operations of this ISR with the new segment buffer.
- Write how the acceleration counters work and why they are set at half via mid-point rule.
- Determine if placing the position counters elsewhere (or change them to 8-bit variables that
are added to the system position counters at the end of a segment) frees up cycles.
- Write a blurb about how the acceleration should be handled within the ISR. All of the
time/step/ramp counters accurately keep track of the remainders and phasing of the variables
with time. This means we do not have to compute them via expensive floating point beforehand.
- Need to do an analysis to determine if these counters are really that much cheaper. At least
find out when it isn't anymore. Particularly when the ISR is at a very high frequency.
- Create NOTE: to describe that the total time in this ISR must be less than the ISR frequency
in its worst case scenario.
*/
ISR(TIMER2_COMPA_vect)
{
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
if (busy) { return; } // The busy-flag is used to avoid reentering this interrupt
// Pulse stepper port pins, if flagged. New block dir will always be set one timer tick
// before any step pulse due to algorithm design.
if (st.execute_step) {
st.execute_step = false;
STEPPING_PORT = ( STEPPING_PORT & ~(DIRECTION_MASK | STEP_MASK) ) | st.out_bits;
TCNT0 = st.step_pulse_time; // Reload Timer0 counter.
TCCR0B = (1<<CS21); // Begin Timer0. Full speed, 1/8 prescaler
}
busy = true;
sei(); // Re-enable interrupts to allow Stepper Port Reset Interrupt to fire on-time.
// NOTE: The remaining code in this ISR will finish before returning to main program.
// If there is no step segment, attempt to pop one from the stepper buffer
if (st.load_flag != LOAD_NOOP) {
// Anything in the buffer? If so, load and initialize next step segment.
if (segment_buffer_head != segment_buffer_tail) {
// Initialize new step segment and load number of steps to execute
st_current_segment = &segment_buffer[segment_buffer_tail];
st.step_count = st_current_segment->n_step;
// If the new segment starts a new planner block, initialize stepper variables and counters.
// NOTE: For new segments only, the step counters are not updated to ensure step phasing is continuous.
if (st.load_flag == LOAD_BLOCK) {
pl_current_block = plan_get_current_block(); // Should always be there. Stepper buffer handles this.
st_current_data = &segment_data[segment_buffer[segment_buffer_tail].st_data_index];
// Initialize direction bits for block. Set execute flag to set directions bits upon next ISR tick.
st.out_bits = pl_current_block->direction_bits ^ settings.invert_mask;
st.execute_step = true;
// Initialize Bresenham line counters
st.counter_x = (pl_current_block->step_event_count >> 1);
st.counter_y = st.counter_x;
st.counter_z = st.counter_x;
// Initialize inverse time, step rate data, and acceleration ramp counters
st.counter_dist = INV_TIME_MULTIPLIER; // dist_per_step always greater than dist_per_tick.
}
st.load_flag = LOAD_NOOP; // Segment motion loaded. Set no-operation flag to skip during execution.
} else {
// Can't discard planner block here if a feed hold stops in middle of block.
st_go_idle();
bit_true(sys.execute,EXEC_CYCLE_STOP); // Flag main program for cycle end
return; // Nothing to do but exit.
}
}
// Iterate inverse time counter. Triggers each Bresenham step event.
st.counter_dist -= st_current_segment->dist_per_tick;
// Execute Bresenham step event, when it's time to do so.
if (st.counter_dist < 0) {
if (st.step_count > 0) { // Block phase correction from executing step.
st.counter_dist += INV_TIME_MULTIPLIER; // Reload inverse time counter
st.out_bits = pl_current_block->direction_bits; // Reset out_bits and reload direction bits
st.execute_step = true;
// Execute step displacement profile by Bresenham line algorithm
st.counter_x -= pl_current_block->steps[X_AXIS];
if (st.counter_x < 0) {
st.out_bits |= (1<<X_STEP_BIT);
st.counter_x += pl_current_block->step_event_count;
if (st.out_bits & (1<<X_DIRECTION_BIT)) { sys.position[X_AXIS]--; }
else { sys.position[X_AXIS]++; }
}
st.counter_y -= pl_current_block->steps[Y_AXIS];
if (st.counter_y < 0) {
st.out_bits |= (1<<Y_STEP_BIT);
st.counter_y += pl_current_block->step_event_count;
if (st.out_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS]--; }
else { sys.position[Y_AXIS]++; }
}
st.counter_z -= pl_current_block->steps[Z_AXIS];
if (st.counter_z < 0) {
st.out_bits |= (1<<Z_STEP_BIT);
st.counter_z += pl_current_block->step_event_count;
if (st.out_bits & (1<<Z_DIRECTION_BIT)) { sys.position[Z_AXIS]--; }
else { sys.position[Z_AXIS]++; }
}
// Check step events for trapezoid change or end of block.
st.step_count--; // Decrement step events count
st.out_bits ^= settings.invert_mask; // Apply step port invert mask
}
}
if (st.step_count == 0) {
if (st.phase_count == 0) {
// Line move is complete, set load line flag to check for new move.
// Check if last line move in planner block. Discard if so.
if (st_current_segment->flag & SEGMENT_END_OF_BLOCK) {
plan_discard_current_block();
st.load_flag = LOAD_BLOCK;
} else {
st.load_flag = LOAD_SEGMENT;
}
// Discard current segment by advancing buffer tail index
if ( ++segment_buffer_tail == SEGMENT_BUFFER_SIZE) { segment_buffer_tail = 0; }
}
st.phase_count--;
}
busy = false;
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
}
// The Stepper Port Reset Interrupt: Timer0 OVF interrupt handles the falling edge of the step
// pulse. This should always trigger before the next Timer2 COMPA interrupt and independently
// finish, if Timer2 is disabled after completing a move.
ISR(TIMER0_OVF_vect)
{
STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | (settings.invert_mask & STEP_MASK);
TCCR0B = 0; // Disable timer until needed.
}
// Reset and clear stepper subsystem variables
void st_reset()
{
memset(&st, 0, sizeof(st));
st.load_flag = LOAD_BLOCK;
busy = false;
pl_current_block = NULL; // Planner block pointer used by stepper algorithm
pl_prep_block = NULL; // Planner block pointer used by segment buffer
pl_prep_index = 0; // Planner buffer indices are also reset to zero.
st_data_prep_index = 0;
segment_buffer_tail = 0;
segment_buffer_head = 0; // empty = tail
segment_next_head = 1;
pl_partial_block_flag = false;
}
// Initialize and start the stepper motor subsystem
void st_init()
{
// Configure directions of interface pins
STEPPING_DDR |= STEPPING_MASK;
STEPPING_PORT = (STEPPING_PORT & ~STEPPING_MASK) | settings.invert_mask;
STEPPERS_DISABLE_DDR |= 1<<STEPPERS_DISABLE_BIT;
// Configure Timer 2
TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt while configuring it
TCCR2B = 0; // Disable Timer2 until needed
TCNT2 = 0; // Clear Timer2 counter
TCCR2A = (1<<WGM21); // Set CTC mode
OCR2A = (F_CPU/ISR_TICKS_PER_SECOND)/8 - 1; // Set Timer2 CTC rate
// Configure Timer 0
TIMSK0 &= ~(1<<TOIE0);
TCCR0A = 0; // Normal operation
TCCR0B = 0; // Disable Timer0 until needed
TIMSK0 |= (1<<TOIE0); // Enable overflow interrupt
// Start in the idle state, but first wake up to check for keep steppers enabled option.
st_wake_up();
st_go_idle();
}
// Planner external interface to start stepper interrupt and execute the blocks in queue. Called
// by the main program functions: planner auto-start and run-time command execution.
void st_cycle_start()
{
if (sys.state == STATE_QUEUED) {
sys.state = STATE_CYCLE;
st_prep_buffer(); // Initialize step segment buffer before beginning cycle.
st_wake_up();
}
}
// Execute a feed hold with deceleration, only during cycle. Called by main program.
void st_feed_hold()
{
if (sys.state == STATE_CYCLE) {
sys.state = STATE_HOLD;
sys.auto_start = false; // Disable planner auto start upon feed hold.
}
}
// Reinitializes the cycle plan and stepper system after a feed hold for a resume. Called by
// runtime command execution in the main program, ensuring that the planner re-plans safely.
// NOTE: Bresenham algorithm variables are still maintained through both the planner and stepper
// cycle reinitializations. The stepper path should continue exactly as if nothing has happened.
// Only the planner de/ac-celerations profiles and stepper rates have been updated.
void st_cycle_reinitialize()
{
// if (pl_current_block != NULL) {
// Replan buffer from the feed hold stop location.
// TODO: Need to add up all of the step events in the current planner block to give
// back to the planner. Should only need it for the current block.
// BUT! The planner block millimeters is all changed and may be changed into the next
// planner block. The block millimeters would need to be recalculated via step counts
// and the mm/step variable.
// OR. Do we plan the feed hold itself down with the planner.
// plan_cycle_reinitialize(st_current_data->step_events_remaining);
// st.ramp_type = RAMP_ACCEL;
// st.counter_ramp = ISR_TICKS_PER_ACCELERATION_TICK/2;
// st.ramp_rate = 0;
// sys.state = STATE_QUEUED;
// } else {
// sys.state = STATE_IDLE;
// }
sys.state = STATE_IDLE;
}
/* Prepares step segment buffer. Continuously called from main program.
The segment buffer is an intermediary buffer interface between the execution of steps
by the stepper algorithm and the velocity profiles generated by the planner. The stepper
algorithm only executes steps within the segment buffer and is filled by the main program
when steps are "checked-out" from the first block in the planner buffer. This keeps the
step execution and planning optimization processes atomic and protected from each other.
The number of steps "checked-out" from the planner buffer and the number of segments in
the segment buffer is sized and computed such that no operation in the main program takes
longer than the time it takes the stepper algorithm to empty it before refilling it.
Currently, the segment buffer conservatively holds roughly up to 40-60 msec of steps.
NOTE: The segment buffer executes a set number of steps over an approximate time period.
If we try to execute over a fixed time period, it is difficult to guarantee or predict
how many steps will execute over it, especially when the step pulse phasing between the
neighboring segments must also be kept consistent. Meaning that, if the last segment step
pulses right before a segment end, the next segment must delay its first pulse so that the
step pulses are consistently spaced apart over time to keep the step pulse train nice and
smooth. Keeping track of phasing and ensuring that the exact number of steps are executed
as defined by the planner block, the related computational overhead can get quickly and
prohibitively expensive, especially in real-time.
Since the stepper algorithm automatically takes care of the step pulse phasing with
its ramp and inverse time counters by retaining the count remainders, we don't have to
explicitly and expensively track and synchronize the exact number of steps, time, and
phasing of steps. All we need to do is approximate the number of steps in each segment
such that the segment buffer has enough execution time for the main program to do what
it needs to do and refill it when it comes back. In other words, we just need to compute
a cheap approximation of the current velocity and the number of steps over it.
*/
/*
TODO: Figure out how to enforce a deceleration when a feedrate override is reduced.
The problem is that when an override is reduced, the planner may not plan back to
the current rate. Meaning that the velocity profiles for certain conditions no longer
are trapezoidal or triangular. For example, if the current block is cruising at a
nominal rate and the feedrate override is reduced, the new nominal rate will now be
lower. The velocity profile must first decelerate to the new nominal rate and then
follow on the new plan. So the remaining velocity profile will have a decelerate,
cruise, and another decelerate.
Another issue is whether or not a feedrate override reduction causes a deceleration
that acts over several planner blocks. For example, say that the plan is already
heavily decelerating throughout it, reducing the feedrate will not do much to it. So,
how do we determine when to resume the new plan? How many blocks do we have to wait
until the new plan intersects with the deceleration curve? One plus though, the
deceleration will never be more than the number of blocks in the entire planner buffer,
but it theoretically can be equal to it when all planner blocks are decelerating already.
*/
void st_prep_buffer()
{
if (sys.state == STATE_QUEUED) { return; } // Block until a motion state is issued
while (segment_buffer_tail != segment_next_head) { // Check if we need to fill the buffer.
// Initialize new segment
st_segment_t *prep_segment = &segment_buffer[segment_buffer_head];
prep_segment->flag = SEGMENT_NOOP;
// -----------------------------------------------------------------------------------
// Determine if we need to load a new planner block. If so, prepare step data.
if (pl_prep_block == NULL) {
pl_prep_block = plan_get_block_by_index(pl_prep_index); // Query planner for a queued block
if (pl_prep_block == NULL) { return; } // No planner blocks. Exit.
// Increment stepper common data index
if ( ++st_data_prep_index == (SEGMENT_BUFFER_SIZE-1) ) { st_data_prep_index = 0; }
// Check if the planner has re-computed this block mid-execution. If so, push the previous
// segment data. Otherwise, prepare a new segment data for the new planner block.
if (pl_partial_block_flag) {
// Prepare new shared segment block data and copy the relevant last segment block data.
st_data_t *last_st_prep_data;
last_st_prep_data = st_prep_data;
st_prep_data = &segment_data[st_data_prep_index];
st_prep_data->step_events_remaining = last_st_prep_data->step_events_remaining;
pl_partial_block_flag = false; // Reset flag
} else {
// Prepare commonly shared planner block data for the ensuing segment buffer moves ad-hoc, since
// the planner buffer can dynamically change the velocity profile data as blocks are added.
st_prep_data = &segment_data[st_data_prep_index];
st_prep_step_per_mm = pl_prep_block->step_event_count/pl_prep_block->millimeters;
// Initialize planner block step data
st_prep_data->step_events_remaining = pl_prep_block->step_event_count;
}
st_prep_data->current_speed = sqrt(pl_prep_block->entry_speed_sqr);
// Determine current block exit speed
plan_block_t *pl_next_block = plan_get_block_by_index(plan_next_block_index(pl_prep_index));
float exit_speed_sqr;
if (pl_next_block == NULL) {
exit_speed_sqr = 0.0;
st_prep_data->exit_speed = 0.0;
} else {
exit_speed_sqr = pl_next_block->entry_speed_sqr;
st_prep_data->exit_speed = sqrt(exit_speed_sqr);
}
// st_prep_data->accelerate_until = 0.5*(pl_prep_block->nominal_speed_sqr-pl_prep_block->entry_speed_sqr)/(pl_prep_block->acceleration);
// st_prep_data->decelerate_after = 0.5*(pl_prep_block->nominal_speed_sqr-exit_speed_sqr)/(pl_prep_block->acceleration);
// if (pl_prep_block->millimeters < st_prep_data->accelerate_until+st_prep_data->decelerate_after) {
// st_prep_data->decelerate_after = 0.5*( pl_prep_block->millimeters + 0.5*(pl_prep_block->entry_speed_sqr
// - exit_speed_sqr)/(pl_prep_block->acceleration) );
// st_prep_data->accelerate_until = pl_prep_block->millimeters-st_prep_data->decelerate_after;
// st_prep_data->maximum_speed = sqrt(2*pl_prep_block->acceleration*st_prep_data->decelerate_after+exit_speed_sqr);
// } else {
// st_prep_data->accelerate_until = pl_prep_block->millimeters-st_prep_data->accelerate_until;
// st_prep_data->maximum_speed = sqrt(pl_prep_block->nominal_speed_sqr);
// }
// Determine velocity profile based on the 7 possible types: Cruise-only, cruise-deceleration,
// acceleration-cruise, acceleration-only, deceleration-only, trapezoid, and triangle.
st_prep_data->accelerate_until = pl_prep_block->millimeters;
if (pl_prep_block->entry_speed_sqr == pl_prep_block->nominal_speed_sqr) {
st_prep_data->maximum_speed = sqrt(pl_prep_block->nominal_speed_sqr);
if (exit_speed_sqr == pl_prep_block->nominal_speed_sqr) { // Cruise-only type
st_prep_data->decelerate_after = 0.0;
} else { // Cruise-deceleration type
st_prep_data->decelerate_after = 0.5*(pl_prep_block->nominal_speed_sqr-exit_speed_sqr)/(pl_prep_block->acceleration);
}
} else if (exit_speed_sqr == pl_prep_block->nominal_speed_sqr) {
// Acceleration-cruise type
st_prep_data->maximum_speed = sqrt(pl_prep_block->nominal_speed_sqr);
st_prep_data->decelerate_after = 0.0;
st_prep_data->accelerate_until -= 0.5*(pl_prep_block->nominal_speed_sqr-pl_prep_block->entry_speed_sqr)/(pl_prep_block->acceleration);
} else {
float intersection_dist = 0.5*( pl_prep_block->millimeters + 0.5*(pl_prep_block->entry_speed_sqr
- exit_speed_sqr)/(pl_prep_block->acceleration) );
if (intersection_dist > 0.0) {
if (intersection_dist < pl_prep_block->millimeters) { // Either trapezoid or triangle types
st_prep_data->decelerate_after = 0.5*(pl_prep_block->nominal_speed_sqr-exit_speed_sqr)/(pl_prep_block->acceleration);
if (st_prep_data->decelerate_after < intersection_dist) { // Trapezoid type
st_prep_data->maximum_speed = sqrt(pl_prep_block->nominal_speed_sqr);
st_prep_data->accelerate_until -= 0.5*(pl_prep_block->nominal_speed_sqr-pl_prep_block->entry_speed_sqr)/(pl_prep_block->acceleration);
} else { // Triangle type
st_prep_data->decelerate_after = intersection_dist;
st_prep_data->maximum_speed = sqrt(2*pl_prep_block->acceleration*st_prep_data->decelerate_after+exit_speed_sqr);
st_prep_data->accelerate_until -= st_prep_data->decelerate_after;
}
} else { // Deceleration-only type
st_prep_data->maximum_speed = st_prep_data->current_speed;
st_prep_data->decelerate_after = pl_prep_block->millimeters;
}
} else { // Acceleration-only type
st_prep_data->maximum_speed = st_prep_data->exit_speed;
st_prep_data->decelerate_after = 0.0;
st_prep_data->accelerate_until = 0.0;
}
}
}
// Set new segment to point to the current segment data block.
prep_segment->st_data_index = st_data_prep_index;
// -----------------------------------------------------------------------------------
// Initialize segment execute distance. Attempt to create a full segment over DT_SEGMENT.
float mm_remaining = pl_prep_block->millimeters;
float dt = DT_SEGMENT;
if (mm_remaining > st_prep_data->accelerate_until) { // Acceleration ramp
mm_remaining -= (st_prep_data->current_speed*DT_SEGMENT
+ pl_prep_block->acceleration*(0.5*DT_SEGMENT*DT_SEGMENT));
if (mm_remaining < st_prep_data->accelerate_until) { // **Incomplete** Acceleration ramp end.
// Acceleration-cruise, acceleration-deceleration ramp junction, or end of block.
mm_remaining = st_prep_data->accelerate_until; // NOTE: 0.0 at EOB
dt = 2*(pl_prep_block->millimeters-mm_remaining)/
(st_prep_data->current_speed+st_prep_data->maximum_speed);
st_prep_data->current_speed = st_prep_data->maximum_speed;
} else { // **Complete** Acceleration only.
st_prep_data->current_speed += pl_prep_block->acceleration*DT_SEGMENT;
}
} else if (mm_remaining <= st_prep_data->decelerate_after) { // Deceleration ramp
mm_remaining -= (st_prep_data->current_speed*DT_SEGMENT
- pl_prep_block->acceleration*(0.5*DT_SEGMENT*DT_SEGMENT));
if (mm_remaining > 0.0) { // **Complete** Deceleration only.
st_prep_data->current_speed -= pl_prep_block->acceleration*DT_SEGMENT;
} else { // **Complete* End of block.
dt = 2*pl_prep_block->millimeters/(st_prep_data->current_speed+st_prep_data->exit_speed);
mm_remaining = 0.0;
// st_prep_data->current_speed = st_prep_data->exit_speed;
}
} else { // Cruising profile
mm_remaining -= st_prep_data->maximum_speed*DT_SEGMENT;
if (mm_remaining < st_prep_data->decelerate_after) { // **Incomplete** End of cruise.
// Cruise-deceleration junction or end of block.
mm_remaining = st_prep_data->decelerate_after; // NOTE: 0.0 at EOB
dt = (pl_prep_block->millimeters-mm_remaining)/st_prep_data->maximum_speed;
} // Otherwise **Complete** Cruising only.
}
// -----------------------------------------------------------------------------------
// If segment is incomplete, attempt to fill the remainder.
// NOTE: Segment remainder always spans a cruise and/or a deceleration ramp.
if (dt < DT_SEGMENT) {
if (mm_remaining > 0.0) { // Skip if end of block.
float last_mm_remaining;
float dt_remainder;
// Fill incomplete segment with an acceleration junction.
if (mm_remaining > st_prep_data->decelerate_after) { // Cruising profile
last_mm_remaining = mm_remaining;
dt_remainder = DT_SEGMENT-dt;
mm_remaining -= st_prep_data->current_speed*dt_remainder;
if (mm_remaining < st_prep_data->decelerate_after) { // **Incomplete**
mm_remaining = st_prep_data->decelerate_after;
dt += (last_mm_remaining-mm_remaining)/st_prep_data->maximum_speed;
// current_speed = maximum_speed;
} else { // **Complete** Segment filled.
dt = DT_SEGMENT;
}
}
// Fill incomplete segment with a deceleration junction.
if (mm_remaining > 0.0) {
if (mm_remaining <= st_prep_data->decelerate_after) { // Deceleration ramp
last_mm_remaining = mm_remaining;
dt_remainder = DT_SEGMENT-dt;
mm_remaining -= (dt_remainder*(st_prep_data->current_speed
- 0.5*pl_prep_block->acceleration*dt_remainder));
if (mm_remaining > 0.0) { // **Complete** Segment filled.
st_prep_data->current_speed -= pl_prep_block->acceleration*dt_remainder;
dt = DT_SEGMENT;
} else { // **Complete** End of block.
mm_remaining = 0.0;
dt += (2*last_mm_remaining/(st_prep_data->current_speed+st_prep_data->exit_speed));
// st_prep_data->current_speed = st_prep_data->exit_speed;
}
}
}
}
}
// -----------------------------------------------------------------------------------
// Compute segment step rate, steps to execute, and step phase correction parameters.
// Convert segment distance in terms of steps.
// float dist_travel = pl_prep_block->millimeters;
// if (mm_remaining > 0.0) { dist_travel -= mm_remaining; }
if (mm_remaining > 0.0) {
float steps_remaining = st_prep_step_per_mm*mm_remaining;
prep_segment->dist_per_tick = ceil( (INV_TIME_MULTIPLIER/ISR_TICKS_PER_SECOND)*
(st_prep_data->step_events_remaining-steps_remaining)/dt ); // (mult*step/isr_tic)
// Compute number of steps to execute and segment step phase correction.
prep_segment->n_step = ceil(st_prep_data->step_events_remaining)-ceil(steps_remaining);
prep_segment->n_phase_tick = ceil(INV_TIME_MULTIPLIER*(ceil(steps_remaining)-steps_remaining)/prep_segment->dist_per_tick);
// Update step execution variables
st_prep_data->step_events_remaining = steps_remaining;
pl_prep_block->millimeters = mm_remaining;
} else { // End of block. Finish it out.
prep_segment->dist_per_tick = ceil( (INV_TIME_MULTIPLIER/ISR_TICKS_PER_SECOND)*
st_prep_data->step_events_remaining/dt ); // (mult*step/isr_tic)
// Set to execute the remaining steps and no phase correction upon finishing the block.
prep_segment->n_step = ceil(st_prep_data->step_events_remaining);
prep_segment->n_phase_tick = 0;
// NOTE: Not required. Planner will ignore this block as it is now complete.
// st_prep_data->step_events_remaining = 0.0;
// pl_prep_block->millimeters = 0.0;
// Move planner pointer to next block and flag to load a new block for the next segment.
pl_prep_index = plan_next_block_index(pl_prep_index);
pl_prep_block = NULL;
prep_segment->flag |= SEGMENT_END_OF_BLOCK;
}
// !!! PROBLEM. Step events remaining in floating point can limit the number of steps
// we can accurately track, since floats have ~7.2 significant digits. However, this only
// becomes a problem if there are more than 1,000,000, which translates to a CNC machine
// with 200 step/mm and 5 meters of axis travel. Possible but unlikely. Could have more
// issues with user setting up their machine with too high of steps.
// TODO: dist_per_tick must be less than INV_TIME_MULTIPLIER. A check can be made to
// make this a hard limit. Need to make sure this doesn't affect the velocity profiles..
// it shouldn't. The same could said for the minimum allowable step rate too. This should
// not affect the tracing of the profiles either.
// Ensure the initial step rate exceeds the MINIMUM_STEP_RATE.
// TODO: Use config.h error checking to do this. Otherwise, counters get screwy.
// New step segment initialization completed. Increment segment buffer indices.
segment_buffer_head = segment_next_head;
if ( ++segment_next_head == SEGMENT_BUFFER_SIZE ) { segment_next_head = 0; }
SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT;
}
}
uint8_t st_get_prep_block_index()
{
// Returns only the index but doesn't state if the block has been partially executed. How do we simply check for this?
return(pl_prep_index);
}
void st_update_plan_block_parameters()
{
if (pl_prep_block != NULL) { // Ignore if at start of a new block.
plan_block_t *pl_partial_block = plan_get_block_by_index(pl_prep_index); // Point to partially completed block
pl_partial_block->entry_speed_sqr = st_prep_data->current_speed*st_prep_data->current_speed;
// pl_partial_block->max_entry_speed_sqr = pl_partial_block->entry_speed_sqr; // Not sure if this needs to be updated.
// Flag for new prep_block when st_prep_buffer() is called after the planner recomputes.
pl_partial_block_flag = true;
pl_prep_block = NULL;
}
return;
}