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stepper.c
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/*
stepper.c - stepper motor driver: executes motion plans using stepper motors
Part of grblHAL
Copyright (c) 2016-2025 Terje Io
Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
Copyright (c) 2009-2011 Simen Svale Skogsrud
grblHAL 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.
grblHAL 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 grblHAL. If not, see <http://www.gnu.org/licenses/>.
*/
#include <math.h>
#include <stdlib.h>
#include <string.h>
#include "hal.h"
#include "protocol.h"
#include "state_machine.h"
//#define MINIMIZE_PROBE_OVERSHOOT
//#include "debug.h"
//! \cond
// Some useful constants.
#define DT_SEGMENT (1.0f / (ACCELERATION_TICKS_PER_SECOND * 60.0f)) // min/segment
#define REQ_MM_INCREMENT_SCALAR 1.25f
typedef enum {
Ramp_Accel,
Ramp_Cruise,
Ramp_Decel,
Ramp_DecelOverride
} ramp_type_t;
typedef union {
uint8_t flags;
struct {
uint8_t velocity_profile :1,
hold_partial_block :1,
parking :1,
decel_override :1,
unassigned :4;
};
} prep_flags_t;
// Holds 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. Also, AMASS alters this
// data for its own use.
static st_block_t st_block_buffer[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.
static segment_t segment_buffer[SEGMENT_BUFFER_SIZE];
// Stepper ISR data struct. Contains the running data for the main stepper ISR.
static stepper_t st;
#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
typedef struct {
uint32_t level_1;
uint32_t level_2;
uint32_t level_3;
} amass_t;
static amass_t amass;
#endif
// Used for blocking new segments being added to the seqment buffer until deceleration starts
// after probe signal has been asserted.
static volatile bool probe_asserted = false;
// Stepper timer ticks per minute
static float cycles_per_min;
// Step segment ring buffer pointers
static volatile segment_t *segment_buffer_tail;
static segment_t *segment_buffer_head, *segment_next_head;
#if ENABLE_JERK_ACCELERATION
// Static storage for acceleration value of last computed segment.
static float last_segment_accel = 0.0f;
#endif
// 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
static st_block_t st_hold_block; // Copy of stepper block data for block put on hold during parking
// Segment preparation data struct. Contains all the necessary information to compute new segments
// based on the current executing planner block.
typedef struct {
prep_flags_t recalculate;
float dt_remainder;
uint32_t steps_remaining;
float steps_per_mm;
float req_mm_increment;
st_block_t *last_st_block;
uint32_t last_steps_remaining;
float last_steps_per_mm;
float last_dt_remainder;
ramp_type_t ramp_type; // Current segment ramp state
float mm_complete; // End of velocity profile from end of current planner block in (mm).
// NOTE: This value must coincide with a step(no mantissa) when converted.
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)
#ifdef KINEMATICS_API
float rate_multiplier; // Rate multiplier of executing block.
#endif
float accelerate_until; // Acceleration ramp end measured from end of block (mm)
float decelerate_after; // Deceleration ramp start measured from end of block (mm)
float target_position; //
float target_feed; //
float inv_feedrate; // Used by PWM laser mode to speed up segment calculations.
float current_spindle_rpm;
} st_prep_t;
//! \endcond
static st_prep_t prep;
extern void gc_output_message (char *message);
/* BLOCK VELOCITY PROFILE DEFINITION
__________________________
/| |\ _________________ ^
/ | | \ /| |\ |
/ | | \ / | | \ s
/ | | | | | \ p
/ | | | | | \ e
+-----+------------------------+---+--+---------------+----+ e
| BLOCK 1 ^ BLOCK 2 | d
|
time -----> EXAMPLE: Block 2 entry speed is at max junction velocity
The planner block buffer is planned assuming constant acceleration velocity profiles and are
continuously joined at block junctions as shown above. However, the planner only actively computes
the block entry speeds for an optimal velocity plan, but does not compute the block internal
velocity profiles. These velocity profiles are computed ad-hoc as they are executed by the
stepper algorithm and consists of only 7 possible types of profiles: cruise-only, cruise-
deceleration, acceleration-cruise, acceleration-only, deceleration-only, full-trapezoid, and
triangle(no cruise).
maximum_speed (< nominal_speed) -> +
+--------+ <- maximum_speed (= nominal_speed) /|\
/ \ / | \
current_speed -> + \ / | + <- exit_speed
| + <- exit_speed / | |
+-------------+ current_speed -> +----+--+
time --> ^ ^ ^ ^
| | | |
decelerate_after(in mm) decelerate_after(in mm)
^ ^ ^ ^
| | | |
accelerate_until(in mm) accelerate_until(in mm)
The step segment buffer computes the executing block velocity profile and tracks the critical
parameters for the stepper algorithm to accurately trace the profile. These critical parameters
are shown and defined in the above illustration.
*/
//
// Callback from delay to deenergize steppers after movement, might been cancelled
void st_deenergize (void *data)
{
if(sys.steppers_deenergize) {
hal.stepper.enable(settings.steppers.energize, true);
sys.steppers_deenergize = false;
}
}
// 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 (void)
{
// Initialize stepper data to ensure first ISR call does not step and
// cancel any pending steppers deenergize
//st.exec_block = NULL;
sys.steppers_deenergize = false;
hal.stepper.wake_up();
}
// Stepper shutdown
ISR_CODE void ISR_FUNC(st_go_idle)(void)
{
// Disable Stepper Driver Interrupt. Allow Stepper Port Reset Interrupt to finish, if active.
sys_state_t state = state_get();
hal.stepper.go_idle(false);
// Set stepper driver idle state, disabled or enabled, depending on settings and circumstances.
if(((settings.steppers.idle_lock_time != 255) || sys.rt_exec_alarm || state == STATE_SLEEP) && state != STATE_HOMING) {
if(settings.steppers.idle_lock_time == 0 || state == STATE_SLEEP)
hal.stepper.enable((axes_signals_t){0}, true);
else {
// 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.
task_delete(st_deenergize, NULL); // Cancel any pending steppers deenergize task
sys.steppers_deenergize = task_add_delayed(st_deenergize, NULL, settings.steppers.idle_lock_time);
}
} else
hal.stepper.enable(settings.steppers.idle_lock_time == 255 ? (axes_signals_t){AXES_BITMASK} : settings.steppers.energize, true);
}
/* "The Stepper Driver Interrupt" - This timer interrupt is the workhorse of grblHAL. grblHAL employs
the venerable Bresenham line algorithm to manage and exactly synchronize multi-axis moves.
Unlike the popular DDA algorithm, the Bresenham algorithm is not susceptible to numerical
round-off errors and only requires fast integer counters, meaning low computational overhead
and maximizing the microcontrollers capabilities. However, the downside of the Bresenham algorithm
is, for certain multi-axis motions, the non-dominant axes may suffer from un-smooth step
pulse trains, or aliasing, which can lead to strange audible noises or shaking. This is
particularly noticeable or may cause motion issues at low step frequencies (0-5kHz), but
is usually not a physical problem at higher frequencies, although audible.
To improve Bresenham multi-axis performance, grblHAL uses what we call an Adaptive Multi-Axis
Step Smoothing (AMASS) algorithm, which does what the name implies. At lower step frequencies,
AMASS artificially increases the Bresenham resolution without effecting the algorithm's
innate exactness. AMASS adapts its resolution levels automatically depending on the step
frequency to be executed, meaning that for even lower step frequencies the step smoothing
level increases. Algorithmically, AMASS is achieved by a simple bit-shifting of the Bresenham
step count for each AMASS level. For example, for a Level 1 step smoothing, we bit shift
the Bresenham step event count, effectively multiplying it by 2, while the axis step counts
remain the same, and then double the stepper ISR frequency. In effect, we are allowing the
non-dominant Bresenham axes step in the intermediate ISR tick, while the dominant axis is
stepping every two ISR ticks, rather than every ISR tick in the traditional sense. At AMASS
Level 2, we simply bit-shift again, so the non-dominant Bresenham axes can step within any
of the four ISR ticks, the dominant axis steps every four ISR ticks, and quadruple the
stepper ISR frequency. And so on. This, in effect, virtually eliminates multi-axis aliasing
issues with the Bresenham algorithm and does not significantly alter grblHAL's performance, but
in fact, more efficiently utilizes unused CPU cycles overall throughout all configurations.
AMASS retains the Bresenham algorithm exactness by requiring that it always executes a full
Bresenham step, regardless of AMASS Level. Meaning that for an AMASS Level 2, all four
intermediate steps must be completed such that baseline Bresenham (Level 0) count is always
retained. Similarly, AMASS Level 3 means all eight intermediate steps must be executed.
Although the AMASS Levels are in reality arbitrary, where the baseline Bresenham counts can
be multiplied by any integer value, multiplication by powers of two are simply used to ease
CPU overhead with bitshift integer operations.
This interrupt is simple and dumb by design. All the computational heavy-lifting, as in
determining accelerations, is performed elsewhere. This interrupt pops pre-computed segments,
defined as constant velocity over n number of steps, from the step segment buffer and then
executes them by pulsing the stepper pins appropriately via the Bresenham algorithm. This
ISR 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 stepper outputs
simultaneously with these two interrupts.
NOTE: This interrupt must be as efficient as possible and complete before the next ISR tick.
NOTE: This ISR expects at least one step to be executed per segment.
*/
//! \cond
ISR_CODE void ISR_FUNC(stepper_driver_interrupt_handler)(void)
{
#if ENABLE_BACKLASH_COMPENSATION
static bool backlash_motion;
#endif
// Start a step pulse when there is a block to execute.
if(st.exec_block) {
hal.stepper.pulse_start(&st);
st.new_block = st.dir_change = false;
if (st.step_count == 0) // Segment is complete. Discard current segment.
st.exec_segment = NULL;
}
// 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_tail != segment_buffer_head) {
// Initialize new step segment and load number of steps to execute
st.exec_segment = (segment_t *)segment_buffer_tail;
// Initialize step segment timing per step and load number of steps to execute.
hal.stepper.cycles_per_tick(st.exec_segment->cycles_per_tick);
st.step_count = st.exec_segment->n_step; // NOTE: Can sometimes be zero when moving slow.
// If the new segment starts a new planner block, initialize stepper variables and counters.
if (st.exec_block != st.exec_segment->exec_block) {
if((st.dir_change = st.exec_block == NULL || st.dir_outbits.value != st.exec_segment->exec_block->direction_bits.value))
st.dir_outbits = st.exec_segment->exec_block->direction_bits;
if(st.exec_block != NULL && st.exec_block->offset_id != st.exec_segment->exec_block->offset_id)
sys.report.wco = sys.report.force_wco = On; // Do not generate grbl.on_rt_reports_added event!
st.exec_block = st.exec_segment->exec_block;
st.step_event_count = st.exec_block->step_event_count;
st.new_block = true;
#if ENABLE_BACKLASH_COMPENSATION
backlash_motion = st.exec_block->backlash_motion;
#endif
if(st.exec_block->overrides.sync)
sys.override.control = st.exec_block->overrides;
// Execute output commands to be synchronized with motion
while(st.exec_block->output_commands) {
output_command_t *cmd = st.exec_block->output_commands;
if(cmd->is_digital)
hal.port.digital_out(cmd->port, cmd->value != 0.0f);
else
hal.port.analog_out(cmd->port, cmd->value);
st.exec_block->output_commands = cmd->next;
}
// Enqueue any message to be printed (by foreground process)
if(st.exec_block->message) {
if(!task_add_immediate((foreground_task_ptr)gc_output_message, st.exec_block->message))
free(st.exec_block->message);
st.exec_block->message = NULL;
}
// Initialize Bresenham line and distance counters
st.counter_x = st.counter_y = st.counter_z
#ifdef A_AXIS
= st.counter_a
#endif
#ifdef B_AXIS
= st.counter_b
#endif
#ifdef C_AXIS
= st.counter_c
#endif
#ifdef U_AXIS
= st.counter_u
#endif
#ifdef V_AXIS
= st.counter_v
#endif
= st.step_event_count >> 1;
#ifndef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
memcpy(st.steps, st.exec_block->steps, sizeof(st.steps));
#endif
}
#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
// With AMASS enabled, adjust Bresenham axis increment counters according to AMASS level.
st.amass_level = st.exec_segment->amass_level;
st.steps[X_AXIS] = st.exec_block->steps[X_AXIS] >> st.amass_level;
st.steps[Y_AXIS] = st.exec_block->steps[Y_AXIS] >> st.amass_level;
st.steps[Z_AXIS] = st.exec_block->steps[Z_AXIS] >> st.amass_level;
#ifdef A_AXIS
st.steps[A_AXIS] = st.exec_block->steps[A_AXIS] >> st.amass_level;
#endif
#ifdef B_AXIS
st.steps[B_AXIS] = st.exec_block->steps[B_AXIS] >> st.amass_level;
#endif
#ifdef C_AXIS
st.steps[C_AXIS] = st.exec_block->steps[C_AXIS] >> st.amass_level;
#endif
#ifdef U_AXIS
st.steps[U_AXIS] = st.exec_block->steps[U_AXIS] >> st.amass_level;
#endif
#ifdef V_AXIS
st.steps[V_AXIS] = st.exec_block->steps[V_AXIS] >> st.amass_level;
#endif
#endif
if(st.exec_segment->update_pwm)
st.exec_segment->update_pwm(st.exec_block->spindle, st.exec_segment->spindle_pwm);
else if(st.exec_segment->update_rpm)
st.exec_segment->update_rpm(st.exec_block->spindle, st.exec_segment->spindle_rpm);
} else {
// Segment buffer empty. Shutdown.
st_go_idle();
// Ensure pwm is set properly upon completion of rate-controlled motion.
if(st.exec_block->dynamic_rpm && st.exec_block->spindle->cap.laser) {
prep.current_spindle_rpm = 0.0f;
st.exec_block->spindle->update_pwm(st.exec_block->spindle, st.exec_block->spindle->pwm_off_value);
}
st.exec_block = NULL;
system_set_exec_state_flag(EXEC_CYCLE_COMPLETE); // Flag main program for cycle complete
return; // Nothing to do but exit.
}
}
// Check probing state.
// Monitors probe pin state and records the system position when detected.
// NOTE: This function must be extremely efficient as to not bog down the stepper ISR.
if (sys.probing_state == Probing_Active && hal.probe.get_state().triggered) {
sys.probing_state = Probing_Off;
memcpy(sys.probe_position, sys.position, sizeof(sys.position));
bit_true(sys.rt_exec_state, EXEC_MOTION_CANCEL);
#ifdef MINIMIZE_PROBE_OVERSHOOT
// "Flush" segment buffer if full in order to start deceleration early.
if((probe_asserted = segment_buffer_head->next == segment_buffer_tail)) {
segment_buffer_head = segment_buffer_tail->next;
if(st.step_count < 3 || st.step_count < (st.exec_segment->n_step >> 3))
segment_buffer_head = segment_buffer_head->next;
segment_next_head = segment_next_head->next;
}
#endif
}
register axes_signals_t step_outbits = (axes_signals_t){0};
// Execute step displacement profile by Bresenham line algorithm
st.counter_x += st.steps[X_AXIS];
if (st.counter_x > st.step_event_count) {
step_outbits.x = On;
st.counter_x -= st.step_event_count;
#if ENABLE_BACKLASH_COMPENSATION
if(!backlash_motion)
#endif
sys.position[X_AXIS] = sys.position[X_AXIS] + (st.dir_outbits.x ? -1 : 1);
}
st.counter_y += st.steps[Y_AXIS];
if (st.counter_y > st.step_event_count) {
step_outbits.y = On;
st.counter_y -= st.step_event_count;
#if ENABLE_BACKLASH_COMPENSATION
if(!backlash_motion)
#endif
sys.position[Y_AXIS] = sys.position[Y_AXIS] + (st.dir_outbits.y ? -1 : 1);
}
st.counter_z += st.steps[Z_AXIS];
if (st.counter_z > st.step_event_count) {
step_outbits.z = On;
st.counter_z -= st.step_event_count;
#if ENABLE_BACKLASH_COMPENSATION
if(!backlash_motion)
#endif
sys.position[Z_AXIS] = sys.position[Z_AXIS] + (st.dir_outbits.z ? -1 : 1);
}
#ifdef A_AXIS
st.counter_a += st.steps[A_AXIS];
if (st.counter_a > st.step_event_count) {
step_outbits.a = On;
st.counter_a -= st.step_event_count;
#if ENABLE_BACKLASH_COMPENSATION
if(!backlash_motion)
#endif
sys.position[A_AXIS] = sys.position[A_AXIS] + (st.dir_outbits.a ? -1 : 1);
}
#endif
#ifdef B_AXIS
st.counter_b += st.steps[B_AXIS];
if (st.counter_b > st.step_event_count) {
step_outbits.b = On;
st.counter_b -= st.step_event_count;
#if ENABLE_BACKLASH_COMPENSATION
if(!backlash_motion)
#endif
sys.position[B_AXIS] = sys.position[B_AXIS] + (st.dir_outbits.b ? -1 : 1);
}
#endif
#ifdef C_AXIS
st.counter_c += st.steps[C_AXIS];
if (st.counter_c > st.step_event_count) {
step_outbits.c = On;
st.counter_c -= st.step_event_count;
#if ENABLE_BACKLASH_COMPENSATION
if(!backlash_motion)
#endif
sys.position[C_AXIS] = sys.position[C_AXIS] + (st.dir_outbits.c ? -1 : 1);
}
#endif
#ifdef U_AXIS
st.counter_u += st.steps[U_AXIS];
if (st.counter_u > st.step_event_count) {
step_outbits.u = On;
st.counter_u -= st.step_event_count;
#if ENABLE_BACKLASH_COMPENSATION
if(!backlash_motion)
#endif
sys.position[U_AXIS] = sys.position[U_AXIS] + (st.dir_outbits.u ? -1 : 1);
}
#endif
#ifdef V_AXIS
st.counter_v += st.steps[V_AXIS];
if (st.counter_v > st.step_event_count) {
step_outbits.v = On;
st.counter_v -= st.step_event_count;
#if ENABLE_BACKLASH_COMPENSATION
if(!backlash_motion)
#endif
sys.position[V_AXIS] = sys.position[V_AXIS] + (st.dir_outbits.v ? -1 : 1);
}
#endif
st.step_outbits.value = step_outbits.value;
// During a homing cycle, lock out and prevent desired axes from moving.
if (state_get() == STATE_HOMING)
st.step_outbits.value &= sys.homing_axis_lock.mask;
if (st.step_count == 0 || --st.step_count == 0) {
// Segment is complete. Advance segment tail pointer.
segment_buffer_tail = segment_buffer_tail->next;
}
}
//! \endcond
// Reset and clear stepper subsystem variables
void st_reset (void)
{
if(hal.probe.configure)
hal.probe.configure(false, false);
// Initialize stepper driver idle state, clear step and direction port pins.
st_go_idle();
// hal.stepper.go_idle(true);
// NOTE: buffer indices starts from 1 for simpler driver coding!
// Set up stepper block ringbuffer as circular linked list and add id
uint_fast8_t idx, idx_max = (sizeof(st_block_buffer) / sizeof(st_block_t)) - 1;
for(idx = 0 ; idx <= idx_max ; idx++) {
st_block_buffer[idx].next = &st_block_buffer[idx == idx_max ? 0 : idx + 1];
st_block_buffer[idx].id = idx + 1;
}
// Set up segments ringbuffer as circular linked list, add id and clear AMASS level
idx_max = (sizeof(segment_buffer) / sizeof(segment_t)) - 1;
for(idx = 0 ; idx <= idx_max ; idx++) {
segment_buffer[idx].next = &segment_buffer[idx == idx_max ? 0 : idx + 1];
segment_buffer[idx].id = idx + 1;
segment_buffer[idx].amass_level = 0;
}
st_prep_block = &st_block_buffer[0];
// Initialize stepper algorithm variables.
pl_block = NULL; // Planner block pointer used by segment buffer
segment_buffer_tail = segment_buffer_head = &segment_buffer[0]; // empty = tail
segment_next_head = segment_buffer_head->next;
memset(&prep, 0, sizeof(st_prep_t));
memset(&st, 0, sizeof(stepper_t));
#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
// TODO: move to driver?
// AMASS_LEVEL0: Normal operation. No AMASS. No upper cutoff frequency. Starts at LEVEL1 cutoff frequency.
// Defined as step timer frequency / Cutoff frequency in Hz
amass.level_1 = hal.f_step_timer / 8000;
amass.level_2 = hal.f_step_timer / 4000;
amass.level_3 = hal.f_step_timer / 2000;
#endif
cycles_per_min = (float)hal.f_step_timer * 60.0f;
}
// Called by spindle_set_state() to inform about RPM changes.
// Used by st_prep_buffer() to determine if spindle needs update when dynamic RPM is called for.
void st_rpm_changed (float rpm)
{
prep.current_spindle_rpm = rpm;
}
// Called by planner_recalculate() when the executing block is updated by the new plan.
void st_update_plan_block_parameters (void)
{
if (pl_block != NULL) { // Ignore if at start of a new block.
prep.recalculate.velocity_profile = On;
pl_block->entry_speed_sqr = prep.current_speed * prep.current_speed; // Update entry speed.
pl_block = NULL; // Flag st_prep_segment() to load and check active velocity profile.
}
}
// Changes the run state of the step segment buffer to execute the special parking motion.
void st_parking_setup_buffer (void)
{
// Store step execution data of partially completed block, if necessary.
if (prep.recalculate.hold_partial_block && !prep.recalculate.parking) {
prep.last_st_block = st_prep_block;
memcpy(&st_hold_block, st_prep_block, sizeof(st_block_t));
prep.last_steps_remaining = prep.steps_remaining;
prep.last_dt_remainder = prep.dt_remainder;
prep.last_steps_per_mm = prep.steps_per_mm;
}
// Set flags to execute a parking motion
prep.recalculate.parking = On;
prep.recalculate.velocity_profile = Off;
pl_block = NULL; // Always reset parking motion to reload new block.
}
// Restores the step segment buffer to the normal run state after a parking motion.
void st_parking_restore_buffer (void)
{
// Restore step execution data and flags of partially completed block, if necessary.
if (prep.recalculate.hold_partial_block) {
memcpy(prep.last_st_block, &st_hold_block, sizeof(st_block_t));
st_prep_block = prep.last_st_block;
prep.steps_remaining = prep.last_steps_remaining;
prep.dt_remainder = prep.last_dt_remainder;
prep.steps_per_mm = prep.last_steps_per_mm;
prep.recalculate.flags = 0;
prep.recalculate.hold_partial_block = prep.recalculate.velocity_profile = On;
prep.req_mm_increment = REQ_MM_INCREMENT_SCALAR / prep.steps_per_mm; // Recompute this value.
} else
prep.recalculate.flags = 0;
pl_block = NULL; // Set to reload next block.
}
/* 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 40-50 msec of steps.
NOTE: Computation units are in steps, millimeters, and minutes.
*/
void st_prep_buffer (void)
{
// Block step prep buffer, while in a suspend state and there is no suspend motion to execute.
if (sys.step_control.end_motion)
return;
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 or if the block needs to be recomputed.
if (pl_block == NULL) {
// Query planner for a queued block
pl_block = sys.step_control.execute_sys_motion ? plan_get_system_motion_block() : plan_get_current_block();
if (pl_block == NULL)
return; // No planner blocks. Exit.
// Check if we need to only recompute the velocity profile or load a new block.
if (prep.recalculate.velocity_profile) {
if(settings.parking.flags.enabled) {
if (prep.recalculate.parking)
prep.recalculate.velocity_profile = Off;
else
prep.recalculate.flags = 0;
} else
prep.recalculate.flags = 0;
} else {
// 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 when the
// segment buffer finishes the prepped block, but the stepper ISR is still executing it.
st_prep_block = st_prep_block->next;
uint_fast8_t idx = N_AXIS;
#ifndef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
do {
idx--;
st_prep_block->steps[idx] = (pl_block->steps[idx] << 1);
} while(idx);
st_prep_block->step_event_count = (pl_block->step_event_count << 1);
#else
// With AMASS enabled, simply bit-shift multiply all Bresenham data by the max AMASS
// level, such that we never divide beyond the original data anywhere in the algorithm.
// If the original data is divided, we can lose a step from integer roundoff.
do {
idx--;
st_prep_block->steps[idx] = pl_block->steps[idx] << MAX_AMASS_LEVEL;
} while(idx);
st_prep_block->step_event_count = pl_block->step_event_count << MAX_AMASS_LEVEL;
#endif
st_prep_block->direction_bits = pl_block->direction_bits;
st_prep_block->programmed_rate = pl_block->programmed_rate;
// st_prep_block->r = pl_block->programmed_rate;
st_prep_block->millimeters = pl_block->millimeters;
st_prep_block->steps_per_mm = (float)pl_block->step_event_count / pl_block->millimeters;
st_prep_block->spindle = pl_block->spindle.hal;
st_prep_block->output_commands = pl_block->output_commands;
st_prep_block->overrides = pl_block->overrides;
st_prep_block->offset_id = pl_block->offset_id;
st_prep_block->backlash_motion = pl_block->condition.backlash_motion;
st_prep_block->message = pl_block->message;
pl_block->message = NULL;
// Initialize segment buffer data for generating the segments.
prep.steps_per_mm = st_prep_block->steps_per_mm;
prep.steps_remaining = pl_block->step_event_count;
prep.req_mm_increment = REQ_MM_INCREMENT_SCALAR / prep.steps_per_mm;
prep.dt_remainder = prep.target_position = 0.0f; // Reset for new segment block
#ifdef KINEMATICS_API
prep.rate_multiplier = pl_block->rate_multiplier;
#endif
if (sys.step_control.execute_hold || prep.recalculate.decel_override) {
// New block loaded mid-hold. Override planner block entry speed to enforce deceleration.
prep.current_speed = prep.exit_speed;
pl_block->entry_speed_sqr = prep.exit_speed * prep.exit_speed;
prep.recalculate.decel_override = Off;
} else
prep.current_speed = sqrtf(pl_block->entry_speed_sqr);
// Setup laser mode variables. RPM rate adjusted motions will always complete a motion with the
// spindle off.
if ((st_prep_block->dynamic_rpm = pl_block->condition.is_rpm_rate_adjusted)) {
// Pre-compute inverse programmed rate to speed up RPM updating per step segment.
prep.inv_feedrate = pl_block->condition.is_laser_ppi_mode ? 1.0f : 1.0f / pl_block->programmed_rate;
} else
st_prep_block->dynamic_rpm = !!pl_block->spindle.css;
}
/* ---------------------------------------------------------------------------------
Compute the velocity profile of a new planner block based on its entry and exit
speeds, or recompute the profile of a partially-completed planner block if the
planner has updated it. For a commanded forced-deceleration, such as from a feed
hold, override the planner velocities and decelerate to the target exit speed.
*/
prep.mm_complete = 0.0f; // Default velocity profile complete at 0.0mm from end of block.
float inv_2_accel = 0.5f / pl_block->acceleration;
if (sys.step_control.execute_hold) { // [Forced Deceleration to Zero Velocity]
// 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;
// Compute decelerate distance relative to end of block.
float decel_dist = pl_block->millimeters - inv_2_accel * pl_block->entry_speed_sqr;
if(decel_dist < -0.0001f) {
// Deceleration through entire planner block. End of feed hold is not in this block.
prep.exit_speed = sqrtf(pl_block->entry_speed_sqr - 2.0f * pl_block->acceleration * pl_block->millimeters);
} else {
prep.mm_complete = decel_dist < 0.0001f ? 0.0f : decel_dist; // End of feed hold.
prep.exit_speed = 0.0f;
}
} else { // [Normal Operation]
// Compute or recompute velocity profile parameters of the prepped planner block.
prep.ramp_type = Ramp_Accel; // Initialize as acceleration ramp.
prep.accelerate_until = pl_block->millimeters;
float exit_speed_sqr;
if (sys.step_control.execute_sys_motion)
prep.exit_speed = exit_speed_sqr = 0.0f; // Enforce stop at end of system motion.
else {
exit_speed_sqr = plan_get_exec_block_exit_speed_sqr();
prep.exit_speed = sqrtf(exit_speed_sqr);
}
float nominal_speed = plan_compute_profile_nominal_speed(pl_block);
float nominal_speed_sqr = nominal_speed * nominal_speed;
float intersect_distance = 0.5f * (pl_block->millimeters + inv_2_accel * (pl_block->entry_speed_sqr - exit_speed_sqr));
prep.target_feed = nominal_speed;
if (pl_block->entry_speed_sqr > nominal_speed_sqr) { // Only occurs during override reductions.
prep.accelerate_until = pl_block->millimeters - inv_2_accel * (pl_block->entry_speed_sqr - nominal_speed_sqr);
if (prep.accelerate_until <= 0.0f) { // Deceleration-only.
prep.ramp_type = Ramp_Decel;
// prep.decelerate_after = pl_block->millimeters;
// prep.maximum_speed = prep.current_speed;
// Compute override block exit speed since it doesn't match the planner exit speed.
prep.exit_speed = sqrtf(pl_block->entry_speed_sqr - 2.0f * pl_block->acceleration * pl_block->millimeters);
prep.recalculate.decel_override = On; // Flag to load next block as deceleration override.
// TODO: Determine correct handling of parameters in deceleration-only.
// Can be tricky since entry speed will be current speed, as in feed holds.
// Also, look into near-zero speed handling issues with this.
} else {
// Decelerate to cruise or cruise-decelerate types. Guaranteed to intersect updated plan.
prep.decelerate_after = inv_2_accel * (nominal_speed_sqr - exit_speed_sqr); // Should always be >= 0.0 due to planner reinit.
prep.maximum_speed = nominal_speed;
prep.ramp_type = Ramp_DecelOverride;
}
} else if (intersect_distance > 0.0f) {
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 * (nominal_speed_sqr - exit_speed_sqr);
if (prep.decelerate_after < intersect_distance) { // Trapezoid type
prep.maximum_speed = nominal_speed;
if (pl_block->entry_speed_sqr == nominal_speed_sqr) {
// Cruise-deceleration or cruise-only type.
prep.ramp_type = Ramp_Cruise;
} else {
// Full-trapezoid or acceleration-cruise types
prep.accelerate_until -= inv_2_accel * (nominal_speed_sqr - pl_block->entry_speed_sqr);
}
} else { // Triangle type
prep.accelerate_until = prep.decelerate_after = intersect_distance;
prep.maximum_speed = sqrtf(2.0f * pl_block->acceleration * intersect_distance + exit_speed_sqr);
}
} else { // Deceleration-only type
prep.ramp_type = Ramp_Decel;
// prep.decelerate_after = pl_block->millimeters;
// prep.maximum_speed = prep.current_speed;
}
} else { // Acceleration-only type
prep.accelerate_until = 0.0f;
// prep.decelerate_after = 0.0f;
prep.maximum_speed = prep.exit_speed;
}
}
if(state_get() != STATE_HOMING)
sys.step_control.update_spindle_rpm |= pl_block->spindle.hal->cap.laser; // Force update whenever updating block in laser mode.
probe_asserted = false;
}
// Block adding new segments after probe is asserted until deceleration is started.
if(probe_asserted)
return;
// Initialize new segment
segment_t *prep_segment = segment_buffer_head;
// Set new segment to point to the current segment data block.
prep_segment->exec_block = st_prep_block;
prep_segment->update_rpm = NULL;
prep_segment->update_pwm = NULL;
/*------------------------------------------------------------------------------------
Compute the average velocity of this new segment by determining the total distance
traveled over the segment time DT_SEGMENT. The following code first attempts to create
a full segment based on the current ramp conditions. If the segment time is incomplete
when terminating at a ramp state change, the code will continue to loop through the
progressing ramp states to fill the remaining segment execution time. However, if
an incomplete segment terminates at the end of the velocity profile, the segment is
considered completed despite having a truncated execution time less than DT_SEGMENT.
The velocity profile is always assumed to progress through the ramp sequence:
acceleration ramp, cruising state, and deceleration ramp. Each ramp's travel distance
may range from zero to the length of the block. Velocity profiles can end either at
the end of planner block (typical) or mid-block at the end of a forced deceleration,
such as from a feed hold.
*/
float dt_max = DT_SEGMENT; // Maximum segment time
float dt = 0.0f; // Initialize segment time
float time_var = dt_max; // Time worker variable
float mm_var; // mm - Distance worker variable
float speed_var; // Speed worker variable
float mm_remaining = pl_block->millimeters; // New segment distance from end of block.
float minimum_mm = mm_remaining - prep.req_mm_increment; // Guarantee at least one step.
#if ENABLE_JERK_ACCELERATION
float time_to_jerk; // time needed for jerk ramp
float jerk_rampdown; // calculated startpoint of jerk rampdown
#endif
if (minimum_mm < 0.0f)
minimum_mm = 0.0f;
do {
switch (prep.ramp_type) {
case Ramp_DecelOverride:
speed_var = pl_block->acceleration * time_var;
if ((prep.current_speed - prep.maximum_speed) <= speed_var) {
// Cruise or cruise-deceleration types only for deceleration override.
mm_remaining = prep.accelerate_until;
time_var = 2.0f * (pl_block->millimeters - mm_remaining) / (prep.current_speed + prep.maximum_speed);
prep.ramp_type = Ramp_Cruise;
prep.current_speed = prep.maximum_speed;
} else {// Mid-deceleration override ramp.
mm_remaining -= time_var * (prep.current_speed - 0.5f * speed_var);
prep.current_speed -= speed_var;
}
break;
case Ramp_Accel:
// NOTE: Acceleration ramp only computes during first do-while loop.
#if ENABLE_JERK_ACCELERATION
time_to_jerk = last_segment_accel / pl_block->jerk;
jerk_rampdown =time_to_jerk * (prep.current_speed + (0.5f * last_segment_accel * time_to_jerk) + (pl_block->jerk * time_to_jerk * time_to_jerk) / 6.0f); //Distance to 0 acceleration at speed (mm == V(0)*T + 1/2 A0*T^2 + 1/6 J*T^3)
if ((mm_remaining - prep.accelerate_until) > jerk_rampdown) {
//+1.0f to avoid divide by 0 speed, minor effect on jerk ramp
// Check if we are on ramp up or ramp down. Ramp down if distance to end of acceleration is less than distance needed to reach 0 acceleration.
// Then limit acceleration change by jerk up to max acceleration and update for next segment.
// Minimum acceleration jerk per time_var to ensure acceleration completes. Acceleration change at end of ramp is in acceptable jerk range.
last_segment_accel = min(last_segment_accel + pl_block->jerk * time_var, pl_block->max_acceleration);
} else {
last_segment_accel = max(last_segment_accel - pl_block->jerk * time_var, pl_block->jerk * time_var);
}
speed_var = last_segment_accel * time_var;
#else
speed_var = pl_block->acceleration * time_var;
#endif
mm_remaining -= time_var * (prep.current_speed + 0.5f * speed_var);
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 = 2.0f * (pl_block->millimeters - mm_remaining) / (prep.current_speed + prep.maximum_speed);
prep.ramp_type = mm_remaining == prep.decelerate_after ? Ramp_Decel : Ramp_Cruise;
prep.current_speed = prep.maximum_speed;
#if ENABLE_JERK_ACCELERATION
last_segment_accel = 0.0f; // reset acceleration variable to 0 for next accel ramp
#endif
} else // Acceleration only.
prep.current_speed += speed_var;
break;
case Ramp_Cruise:
// NOTE: mm_var used to retain the last mm_remaining for incomplete segment time_var calculations.
// NOTE: If maximum_speed*time_var value is too low, round-off can cause mm_var to not change. To
// prevent this, simply enforce a minimum speed threshold in the planner.
mm_var = mm_remaining - prep.maximum_speed * time_var;
if (mm_var < prep.decelerate_after) { // End of cruise.
// Cruise-deceleration junction or end of block.
time_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 as a misc worker variable to prevent errors when near zero speed.
#if ENABLE_JERK_ACCELERATION
time_to_jerk = last_segment_accel / pl_block->jerk;
jerk_rampdown = prep.exit_speed + time_to_jerk * (last_segment_accel - (0.5f * pl_block->jerk * time_to_jerk)); // Speedpoint to start ramping down deceleration. (V = a * t - 1/2 j * t^2)
if (prep.current_speed > jerk_rampdown) {
// Check if we are on ramp up or ramp down. Ramp down if speed is less than speed needed for reaching 0 acceleration.
// Then limit acceleration change by jerk up to max acceleration and update for next segment.
// Minimum acceleration of jerk per time_var to ensure deceleration completes. Acceleration change at end of ramp is in acceptable jerk range.
last_segment_accel = min(last_segment_accel + pl_block->jerk * time_var, pl_block->max_acceleration);
} else {
last_segment_accel = max(last_segment_accel - pl_block->jerk * time_var, pl_block->jerk * time_var);
}
speed_var = last_segment_accel * time_var; // Used as delta speed (mm/min)
#else
speed_var = pl_block->acceleration * time_var; // Used as delta speed (mm/min)
#endif
if (prep.current_speed > speed_var) { // Check if at or below zero speed.
// Compute distance from end of segment to end of block.
mm_var = mm_remaining - time_var * (prep.current_speed - 0.5f * speed_var); // (mm)
if (mm_var > prep.mm_complete) { // Typical case. In deceleration ramp.
mm_remaining = mm_var;
prep.current_speed -= speed_var;
break; // Segment complete. Exit switch-case statement. Continue do-while loop.
}
}
// Otherwise, at end of block or end of forced-deceleration.
time_var = 2.0f * (mm_remaining - prep.mm_complete) / (prep.current_speed + prep.exit_speed);
mm_remaining = prep.mm_complete;
prep.current_speed = prep.exit_speed;
#if ENABLE_JERK_ACCELERATION
last_segment_accel = 0.0f; // reset acceleration variable to 0 for next accel ramp
#endif
}
dt += time_var; // Add computed ramp time to total segment time.
if (dt < dt_max)
time_var = dt_max - dt;// **Incomplete** At ramp junction.
else {
if (mm_remaining > minimum_mm) { // Check for very slow segments with zero steps.
// Increase segment time to ensure at least one step in segment. Override and loop
// through distance calculations until minimum_mm or mm_complete.
dt_max += DT_SEGMENT;
time_var = dt_max - dt;
} else
break; // **Complete** Exit loop. Segment execution time maxed.
}
} while (mm_remaining > prep.mm_complete); // **Complete** Exit loop. Profile complete.
/* -----------------------------------------------------------------------------------