kopia lustrzana https://github.com/gnea/grbl
850 wiersze
45 KiB
C
850 wiersze
45 KiB
C
/*
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stepper.c - stepper motor driver: executes motion plans using stepper motors
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Part of Grbl
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Copyright (c) 2011-2014 Sungeun K. Jeon
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Copyright (c) 2009-2011 Simen Svale Skogsrud
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Grbl is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Grbl is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Grbl. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "system.h"
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#include "nuts_bolts.h"
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#include "stepper.h"
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#include "settings.h"
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#include "planner.h"
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#include "probe.h"
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// Some useful constants.
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#define DT_SEGMENT (1.0/(ACCELERATION_TICKS_PER_SECOND*60.0)) // min/segment
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#define REQ_MM_INCREMENT_SCALAR 1.25
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#define RAMP_ACCEL 0
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#define RAMP_CRUISE 1
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#define RAMP_DECEL 2
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// Define Adaptive Multi-Axis Step-Smoothing(AMASS) levels and cutoff frequencies. The highest level
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// frequency bin starts at 0Hz and ends at its cutoff frequency. The next lower level frequency bin
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// starts at the next higher cutoff frequency, and so on. The cutoff frequencies for each level must
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// be considered carefully against how much it over-drives the stepper ISR, the accuracy of the 16-bit
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// timer, and the CPU overhead. Level 0 (no AMASS, normal operation) frequency bin starts at the
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// Level 1 cutoff frequency and up to as fast as the CPU allows (over 30kHz in limited testing).
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// NOTE: AMASS cutoff frequency multiplied by ISR overdrive factor must not exceed maximum step frequency.
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// NOTE: Current settings are set to overdrive the ISR to no more than 16kHz, balancing CPU overhead
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// and timer accuracy. Do not alter these settings unless you know what you are doing.
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#define MAX_AMASS_LEVEL 3
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// AMASS_LEVEL0: Normal operation. No AMASS. No upper cutoff frequency. Starts at LEVEL1 cutoff frequency.
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#define AMASS_LEVEL1 (F_CPU/8000) // Over-drives ISR (x2). Defined as F_CPU/(Cutoff frequency in Hz)
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#define AMASS_LEVEL2 (F_CPU/4000) // Over-drives ISR (x4)
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#define AMASS_LEVEL3 (F_CPU/2000) // Over-drives ISR (x8)
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// Stores the planner block Bresenham algorithm execution data for the segments in the segment
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// buffer. Normally, this buffer is partially in-use, but, for the worst case scenario, it will
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// never exceed the number of accessible stepper buffer segments (SEGMENT_BUFFER_SIZE-1).
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// NOTE: This data is copied from the prepped planner blocks so that the planner blocks may be
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// discarded when entirely consumed and completed by the segment buffer. Also, AMASS alters this
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// data for its own use.
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typedef struct {
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uint8_t direction_bits;
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uint32_t steps[N_AXIS];
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uint32_t step_event_count;
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} st_block_t;
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static st_block_t st_block_buffer[SEGMENT_BUFFER_SIZE-1];
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// Primary stepper segment ring buffer. Contains small, short line segments for the stepper
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// algorithm to execute, which are "checked-out" incrementally from the first block in the
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// planner buffer. Once "checked-out", the steps in the segments buffer cannot be modified by
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// the planner, where the remaining planner block steps still can.
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typedef struct {
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uint16_t n_step; // Number of step events to be executed for this segment
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uint8_t st_block_index; // Stepper block data index. Uses this information to execute this segment.
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uint16_t cycles_per_tick; // Step distance traveled per ISR tick, aka step rate.
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#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
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uint8_t amass_level; // Indicates AMASS level for the ISR to execute this segment
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#else
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uint8_t prescaler; // Without AMASS, a prescaler is required to adjust for slow timing.
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#endif
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} segment_t;
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static segment_t segment_buffer[SEGMENT_BUFFER_SIZE];
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// Stepper ISR data struct. Contains the running data for the main stepper ISR.
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typedef struct {
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// Used by the bresenham line algorithm
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uint32_t counter_x, // Counter variables for the bresenham line tracer
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counter_y,
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counter_z;
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#ifdef STEP_PULSE_DELAY
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uint8_t step_bits; // Stores out_bits output to complete the step pulse delay
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#endif
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uint8_t execute_step; // Flags step execution for each interrupt.
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uint8_t step_pulse_time; // Step pulse reset time after step rise
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uint8_t step_outbits; // The next stepping-bits to be output
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uint8_t dir_outbits;
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#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
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uint32_t steps[N_AXIS];
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#endif
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uint16_t step_count; // Steps remaining in line segment motion
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uint8_t exec_block_index; // Tracks the current st_block index. Change indicates new block.
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st_block_t *exec_block; // Pointer to the block data for the segment being executed
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segment_t *exec_segment; // Pointer to the segment being executed
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} stepper_t;
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static stepper_t st;
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// Step segment ring buffer indices
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static volatile uint8_t segment_buffer_tail;
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static uint8_t segment_buffer_head;
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static uint8_t segment_next_head;
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// Used to avoid ISR nesting of the "Stepper Driver Interrupt". Should never occur though.
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static volatile uint8_t busy;
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// Pointers for the step segment being prepped from the planner buffer. Accessed only by the
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// main program. Pointers may be planning segments or planner blocks ahead of what being executed.
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static plan_block_t *pl_block; // Pointer to the planner block being prepped
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static st_block_t *st_prep_block; // Pointer to the stepper block data being prepped
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// Segment preparation data struct. Contains all the necessary information to compute new segments
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// based on the current executing planner block.
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typedef struct {
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uint8_t st_block_index; // Index of stepper common data block being prepped
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uint8_t flag_partial_block; // Flag indicating the last block completed. Time to load a new one.
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float steps_remaining;
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float step_per_mm; // Current planner block step/millimeter conversion scalar
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float req_mm_increment;
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float dt_remainder;
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uint8_t ramp_type; // Current segment ramp state
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float mm_complete; // End of velocity profile from end of current planner block in (mm).
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// NOTE: This value must coincide with a step(no mantissa) when converted.
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float current_speed; // Current speed at the end of the segment buffer (mm/min)
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float maximum_speed; // Maximum speed of executing block. Not always nominal speed. (mm/min)
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float exit_speed; // Exit speed of executing block (mm/min)
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float accelerate_until; // Acceleration ramp end measured from end of block (mm)
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float decelerate_after; // Deceleration ramp start measured from end of block (mm)
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} st_prep_t;
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static st_prep_t prep;
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/* BLOCK VELOCITY PROFILE DEFINITION
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__________________________
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/| |\ _________________ ^
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/ | | \ /| |\ |
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/ | | \ / | | \ s
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/ | | | | | \ p
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/ | | | | | \ e
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+-----+------------------------+---+--+---------------+----+ e
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| BLOCK 1 ^ BLOCK 2 | d
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time -----> EXAMPLE: Block 2 entry speed is at max junction velocity
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The planner block buffer is planned assuming constant acceleration velocity profiles and are
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continuously joined at block junctions as shown above. However, the planner only actively computes
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the block entry speeds for an optimal velocity plan, but does not compute the block internal
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velocity profiles. These velocity profiles are computed ad-hoc as they are executed by the
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stepper algorithm and consists of only 7 possible types of profiles: cruise-only, cruise-
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deceleration, acceleration-cruise, acceleration-only, deceleration-only, full-trapezoid, and
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triangle(no cruise).
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maximum_speed (< nominal_speed) -> +
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+--------+ <- maximum_speed (= nominal_speed) /|\
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/ \ / | \
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current_speed -> + \ / | + <- exit_speed
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| + <- exit_speed / | |
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+-------------+ current_speed -> +----+--+
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time --> ^ ^ ^ ^
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decelerate_after(in mm) decelerate_after(in mm)
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^ ^ ^ ^
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accelerate_until(in mm) accelerate_until(in mm)
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The step segment buffer computes the executing block velocity profile and tracks the critical
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parameters for the stepper algorithm to accurately trace the profile. These critical parameters
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are shown and defined in the above illustration.
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*/
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// Stepper state initialization. Cycle should only start if the st.cycle_start flag is
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// enabled. Startup init and limits call this function but shouldn't start the cycle.
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void st_wake_up()
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{
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// Enable stepper drivers.
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if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) { STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT); }
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else { STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT); }
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if (sys.state & (STATE_CYCLE | STATE_HOMING)){
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// Initialize stepper output bits
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st.dir_outbits = settings.dir_invert_mask;
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st.step_outbits = settings.step_invert_mask;
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// Initialize step pulse timing from settings. Here to ensure updating after re-writing.
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#ifdef STEP_PULSE_DELAY
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// Set total step pulse time after direction pin set. Ad hoc computation from oscilloscope.
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st.step_pulse_time = -(((settings.pulse_microseconds+STEP_PULSE_DELAY-2)*TICKS_PER_MICROSECOND) >> 3);
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// Set delay between direction pin write and step command.
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OCR0A = -(((settings.pulse_microseconds)*TICKS_PER_MICROSECOND) >> 3);
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#else // Normal operation
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// Set step pulse time. Ad hoc computation from oscilloscope. Uses two's complement.
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st.step_pulse_time = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND) >> 3);
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#endif
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// Enable Stepper Driver Interrupt
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TIMSK1 |= (1<<OCIE1A);
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}
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}
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// Stepper shutdown
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void st_go_idle()
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{
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// Disable Stepper Driver Interrupt. Allow Stepper Port Reset Interrupt to finish, if active.
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TIMSK1 &= ~(1<<OCIE1A); // Disable Timer1 interrupt
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TCCR1B = (TCCR1B & ~((1<<CS12) | (1<<CS11))) | (1<<CS10); // Reset clock to no prescaling.
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busy = false;
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// Set stepper driver idle state, disabled or enabled, depending on settings and circumstances.
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bool pin_state = false; // Keep enabled.
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if (((settings.stepper_idle_lock_time != 0xff) || bit_istrue(sys.execute,EXEC_ALARM)) && sys.state != STATE_HOMING) {
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// Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
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// stop and not drift from residual inertial forces at the end of the last movement.
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delay_ms(settings.stepper_idle_lock_time);
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pin_state = true; // Override. Disable steppers.
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}
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if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) { pin_state = !pin_state; } // Apply pin invert.
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if (pin_state) { STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT); }
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else { STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT); }
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}
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/* "The Stepper Driver Interrupt" - This timer interrupt is the workhorse of Grbl. Grbl employs
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the venerable Bresenham line algorithm to manage and exactly synchronize multi-axis moves.
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Unlike the popular DDA algorithm, the Bresenham algorithm is not susceptible to numerical
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round-off errors and only requires fast integer counters, meaning low computational overhead
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and maximizing the Arduino's capabilities. However, the downside of the Bresenham algorithm
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is, for certain multi-axis motions, the non-dominant axes may suffer from un-smooth step
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pulse trains, or aliasing, which can lead to strange audible noises or shaking. This is
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particularly noticeable or may cause motion issues at low step frequencies (0-5kHz), but
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is usually not a physical problem at higher frequencies, although audible.
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To improve Bresenham multi-axis performance, Grbl uses what we call an Adaptive Multi-Axis
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Step Smoothing (AMASS) algorithm, which does what the name implies. At lower step frequencies,
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AMASS artificially increases the Bresenham resolution without effecting the algorithm's
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innate exactness. AMASS adapts its resolution levels automatically depending on the step
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frequency to be executed, meaning that for even lower step frequencies the step smoothing
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level increases. Algorithmically, AMASS is acheived by a simple bit-shifting of the Bresenham
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step count for each AMASS level. For example, for a Level 1 step smoothing, we bit shift
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the Bresenham step event count, effectively multiplying it by 2, while the axis step counts
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remain the same, and then double the stepper ISR frequency. In effect, we are allowing the
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non-dominant Bresenham axes step in the intermediate ISR tick, while the dominant axis is
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stepping every two ISR ticks, rather than every ISR tick in the traditional sense. At AMASS
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Level 2, we simply bit-shift again, so the non-dominant Bresenham axes can step within any
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of the four ISR ticks, the dominant axis steps every four ISR ticks, and quadruple the
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stepper ISR frequency. And so on. This, in effect, virtually eliminates multi-axis aliasing
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issues with the Bresenham algorithm and does not significantly alter Grbl's performance, but
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in fact, more efficiently utilizes unused CPU cycles overall throughout all configurations.
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AMASS retains the Bresenham algorithm exactness by requiring that it always executes a full
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Bresenham step, regardless of AMASS Level. Meaning that for an AMASS Level 2, all four
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intermediate steps must be completed such that baseline Bresenham (Level 0) count is always
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retained. Similarly, AMASS Level 3 means all eight intermediate steps must be executed.
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Although the AMASS Levels are in reality arbitrary, where the baseline Bresenham counts can
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be multiplied by any integer value, multiplication by powers of two are simply used to ease
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CPU overhead with bitshift integer operations.
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This interrupt is simple and dumb by design. All the computational heavy-lifting, as in
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determining accelerations, is performed elsewhere. This interrupt pops pre-computed segments,
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defined as constant velocity over n number of steps, from the step segment buffer and then
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executes them by pulsing the stepper pins appropriately via the Bresenham algorithm. This
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ISR is supported by The Stepper Port Reset Interrupt which it uses to reset the stepper port
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after each pulse. The bresenham line tracer algorithm controls all stepper outputs
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simultaneously with these two interrupts.
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NOTE: This interrupt must be as efficient as possible and complete before the next ISR tick,
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which for Grbl must be less than 33.3usec (@30kHz ISR rate). Oscilloscope measured time in
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ISR is 5usec typical and 25usec maximum, well below requirement.
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NOTE: This ISR expects at least one step to be executed per segment.
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*/
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// TODO: Replace direct updating of the int32 position counters in the ISR somehow. Perhaps use smaller
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// int8 variables and update position counters only when a segment completes. This can get complicated
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// with probing and homing cycles that require true real-time positions.
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ISR(TIMER1_COMPA_vect)
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{
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// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
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if (busy) { return; } // The busy-flag is used to avoid reentering this interrupt
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// Set the direction pins a couple of nanoseconds before we step the steppers
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DIRECTION_PORT = (DIRECTION_PORT & ~DIRECTION_MASK) | (st.dir_outbits & DIRECTION_MASK);
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// Then pulse the stepping pins
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#ifdef STEP_PULSE_DELAY
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st.step_bits = (STEP_PORT & ~STEP_MASK) | st.step_outbits; // Store out_bits to prevent overwriting.
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#else // Normal operation
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STEP_PORT = (STEP_PORT & ~STEP_MASK) | st.step_outbits;
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#endif
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// Enable step pulse reset timer so that The Stepper Port Reset Interrupt can reset the signal after
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// exactly settings.pulse_microseconds microseconds, independent of the main Timer1 prescaler.
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TCNT0 = st.step_pulse_time; // Reload Timer0 counter
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TCCR0B = (1<<CS01); // Begin Timer0. Full speed, 1/8 prescaler
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busy = true;
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sei(); // Re-enable interrupts to allow Stepper Port Reset Interrupt to fire on-time.
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// NOTE: The remaining code in this ISR will finish before returning to main program.
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// If there is no step segment, attempt to pop one from the stepper buffer
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if (st.exec_segment == NULL) {
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// Anything in the buffer? If so, load and initialize next step segment.
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if (segment_buffer_head != segment_buffer_tail) {
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// Initialize new step segment and load number of steps to execute
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st.exec_segment = &segment_buffer[segment_buffer_tail];
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#ifndef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
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// With AMASS is disabled, set timer prescaler for segments with slow step frequencies (< 250Hz).
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TCCR1B = (TCCR1B & ~(0x07<<CS10)) | (st.exec_segment->prescaler<<CS10);
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#endif
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// Initialize step segment timing per step and load number of steps to execute.
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OCR1A = st.exec_segment->cycles_per_tick;
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st.step_count = st.exec_segment->n_step; // NOTE: Can sometimes be zero when moving slow.
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// If the new segment starts a new planner block, initialize stepper variables and counters.
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// NOTE: When the segment data index changes, this indicates a new planner block.
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if ( st.exec_block_index != st.exec_segment->st_block_index ) {
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st.exec_block_index = st.exec_segment->st_block_index;
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st.exec_block = &st_block_buffer[st.exec_block_index];
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// Initialize Bresenham line and distance counters
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st.counter_x = (st.exec_block->step_event_count >> 1);
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st.counter_y = st.counter_x;
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st.counter_z = st.counter_x;
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}
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st.dir_outbits = st.exec_block->direction_bits ^ settings.dir_invert_mask;
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#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
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// With AMASS enabled, adjust Bresenham axis increment counters according to AMASS level.
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st.steps[X_AXIS] = st.exec_block->steps[X_AXIS] >> st.exec_segment->amass_level;
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st.steps[Y_AXIS] = st.exec_block->steps[Y_AXIS] >> st.exec_segment->amass_level;
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st.steps[Z_AXIS] = st.exec_block->steps[Z_AXIS] >> st.exec_segment->amass_level;
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#endif
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} else {
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// Segment buffer empty. Shutdown.
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st_go_idle();
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bit_true(sys.execute,EXEC_CYCLE_STOP); // Flag main program for cycle end
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return; // Nothing to do but exit.
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}
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}
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// Check probing state.
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probe_state_monitor();
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// Reset step out bits.
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st.step_outbits = 0;
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// Execute step displacement profile by Bresenham line algorithm
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#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
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st.counter_x += st.steps[X_AXIS];
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#else
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st.counter_x += st.exec_block->steps[X_AXIS];
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#endif
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if (st.counter_x > st.exec_block->step_event_count) {
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st.step_outbits |= (1<<X_STEP_BIT);
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st.counter_x -= st.exec_block->step_event_count;
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if (st.exec_block->direction_bits & (1<<X_DIRECTION_BIT)) { sys.position[X_AXIS]--; }
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else { sys.position[X_AXIS]++; }
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}
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#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
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st.counter_y += st.steps[Y_AXIS];
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#else
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st.counter_y += st.exec_block->steps[Y_AXIS];
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#endif
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if (st.counter_y > st.exec_block->step_event_count) {
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st.step_outbits |= (1<<Y_STEP_BIT);
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st.counter_y -= st.exec_block->step_event_count;
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if (st.exec_block->direction_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS]--; }
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else { sys.position[Y_AXIS]++; }
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}
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#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
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st.counter_z += st.steps[Z_AXIS];
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#else
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st.counter_z += st.exec_block->steps[Z_AXIS];
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#endif
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if (st.counter_z > st.exec_block->step_event_count) {
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st.step_outbits |= (1<<Z_STEP_BIT);
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st.counter_z -= st.exec_block->step_event_count;
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if (st.exec_block->direction_bits & (1<<Z_DIRECTION_BIT)) { sys.position[Z_AXIS]--; }
|
|
else { sys.position[Z_AXIS]++; }
|
|
}
|
|
|
|
// During a homing cycle, lock out and prevent desired axes from moving.
|
|
if (sys.state == STATE_HOMING) { st.step_outbits &= sys.homing_axis_lock; }
|
|
|
|
st.step_count--; // Decrement step events count
|
|
if (st.step_count == 0) {
|
|
// 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; }
|
|
}
|
|
|
|
st.step_outbits ^= settings.step_invert_mask; // Apply step port invert mask
|
|
busy = false;
|
|
// SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
|
|
}
|
|
|
|
|
|
/* The Stepper Port Reset Interrupt: Timer0 OVF interrupt handles the falling edge of the step
|
|
pulse. This should always trigger before the next Timer1 COMPA interrupt and independently
|
|
finish, if Timer1 is disabled after completing a move.
|
|
NOTE: Interrupt collisions between the serial and stepper interrupts can cause delays by
|
|
a few microseconds, if they execute right before one another. Not a big deal, but can
|
|
cause issues at high step rates if another high frequency asynchronous interrupt is
|
|
added to Grbl.
|
|
*/
|
|
// This interrupt is enabled by ISR_TIMER1_COMPAREA when it sets the motor port bits to execute
|
|
// a step. This ISR resets the motor port after a short period (settings.pulse_microseconds)
|
|
// completing one step cycle.
|
|
ISR(TIMER0_OVF_vect)
|
|
{
|
|
// Reset stepping pins (leave the direction pins)
|
|
STEP_PORT = (STEP_PORT & ~STEP_MASK) | (settings.step_invert_mask & STEP_MASK);
|
|
TCCR0B = 0; // Disable Timer0 to prevent re-entering this interrupt when it's not needed.
|
|
}
|
|
#ifdef STEP_PULSE_DELAY
|
|
// This interrupt is used only when STEP_PULSE_DELAY is enabled. Here, the step pulse is
|
|
// initiated after the STEP_PULSE_DELAY time period has elapsed. The ISR TIMER2_OVF interrupt
|
|
// will then trigger after the appropriate settings.pulse_microseconds, as in normal operation.
|
|
// The new timing between direction, step pulse, and step complete events are setup in the
|
|
// st_wake_up() routine.
|
|
ISR(TIMER0_COMPA_vect)
|
|
{
|
|
STEP_PORT = st.step_bits; // Begin step pulse.
|
|
}
|
|
#endif
|
|
|
|
|
|
// Reset and clear stepper subsystem variables
|
|
void st_reset()
|
|
{
|
|
// Initialize stepper driver idle state.
|
|
st_go_idle();
|
|
|
|
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 stepper_init()
|
|
{
|
|
// Configure step and direction interface pins
|
|
STEP_DDR |= STEP_MASK;
|
|
STEP_PORT = (STEP_PORT & ~STEP_MASK) | settings.step_invert_mask;
|
|
STEPPERS_DISABLE_DDR |= 1<<STEPPERS_DISABLE_BIT;
|
|
DIRECTION_DDR |= DIRECTION_MASK;
|
|
DIRECTION_PORT = (DIRECTION_PORT & ~DIRECTION_MASK) | settings.dir_invert_mask;
|
|
|
|
// Configure Timer 1: Stepper Driver Interrupt
|
|
TCCR1B &= ~(1<<WGM13); // waveform generation = 0100 = CTC
|
|
TCCR1B |= (1<<WGM12);
|
|
TCCR1A &= ~((1<<WGM11) | (1<<WGM10));
|
|
TCCR1A &= ~((1<<COM1A1) | (1<<COM1A0) | (1<<COM1B1) | (1<<COM1B0)); // Disconnect OC1 output
|
|
// TCCR1B = (TCCR1B & ~((1<<CS12) | (1<<CS11))) | (1<<CS10); // Set in st_go_idle().
|
|
// TIMSK1 &= ~(1<<OCIE1A); // Set in st_go_idle().
|
|
|
|
// Configure Timer 0: Stepper Port Reset Interrupt
|
|
TIMSK0 &= ~((1<<OCIE0B) | (1<<OCIE0A) | (1<<TOIE0)); // Disconnect OC0 outputs and OVF interrupt.
|
|
TCCR0A = 0; // Normal operation
|
|
TCCR0B = 0; // Disable Timer0 until needed
|
|
TIMSK0 |= (1<<TOIE0); // Enable Timer0 overflow interrupt
|
|
#ifdef STEP_PULSE_DELAY
|
|
TIMSK0 |= (1<<OCIE0A); // Enable Timer0 Compare Match A interrupt
|
|
#endif
|
|
}
|
|
|
|
|
|
// Called by planner_recalculate() when the executing block is updated by the new plan.
|
|
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->entry_speed_sqr = prep.current_speed*prep.current_speed; // Update entry speed.
|
|
pl_block = NULL; // Flag st_prep_segment() to load new velocity profile.
|
|
}
|
|
}
|
|
|
|
|
|
/* 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()
|
|
{
|
|
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 has been 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.
|
|
|
|
// Check if the segment buffer completed the last planner block. If so, load the Bresenham
|
|
// data for the block. If not, we are still mid-block and the velocity profile was updated.
|
|
if (prep.flag_partial_block) {
|
|
prep.flag_partial_block = false; // Reset flag
|
|
} else {
|
|
// Increment stepper common data index to store new planner block data.
|
|
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 when the
|
|
// segment buffer finishes the prepped block, but the stepper ISR is still executing it.
|
|
st_prep_block = &st_block_buffer[prep.st_block_index];
|
|
st_prep_block->direction_bits = pl_block->direction_bits;
|
|
#ifndef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
|
|
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->step_event_count = pl_block->step_event_count;
|
|
#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.
|
|
st_prep_block->steps[X_AXIS] = pl_block->steps[X_AXIS] << MAX_AMASS_LEVEL;
|
|
st_prep_block->steps[Y_AXIS] = pl_block->steps[Y_AXIS] << MAX_AMASS_LEVEL;
|
|
st_prep_block->steps[Z_AXIS] = pl_block->steps[Z_AXIS] << MAX_AMASS_LEVEL;
|
|
st_prep_block->step_event_count = pl_block->step_event_count << MAX_AMASS_LEVEL;
|
|
#endif
|
|
|
|
// Initialize segment buffer data for generating the segments.
|
|
prep.steps_remaining = pl_block->step_event_count;
|
|
prep.step_per_mm = prep.steps_remaining/pl_block->millimeters;
|
|
prep.req_mm_increment = REQ_MM_INCREMENT_SCALAR/prep.step_per_mm;
|
|
|
|
prep.dt_remainder = 0.0; // Reset for new planner block
|
|
|
|
if (sys.state == STATE_HOLD) {
|
|
// Override planner block entry speed and enforce deceleration during feed hold.
|
|
prep.current_speed = prep.exit_speed;
|
|
pl_block->entry_speed_sqr = prep.exit_speed*prep.exit_speed;
|
|
}
|
|
else { prep.current_speed = sqrt(pl_block->entry_speed_sqr); }
|
|
}
|
|
|
|
/* ---------------------------------------------------------------------------------
|
|
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 = 0.0; // Default velocity profile complete at 0.0mm from end of block.
|
|
float inv_2_accel = 0.5/pl_block->acceleration;
|
|
if (sys.state == STATE_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 < 0.0) {
|
|
// Deceleration through entire planner block. End of feed hold is not in this block.
|
|
prep.exit_speed = sqrt(pl_block->entry_speed_sqr-2*pl_block->acceleration*pl_block->millimeters);
|
|
} else {
|
|
prep.mm_complete = decel_dist; // End of feed hold.
|
|
prep.exit_speed = 0.0;
|
|
}
|
|
} 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;
|
|
prep.exit_speed = plan_get_exec_block_exit_speed();
|
|
float exit_speed_sqr = prep.exit_speed*prep.exit_speed;
|
|
float intersect_distance =
|
|
0.5*(pl_block->millimeters+inv_2_accel*(pl_block->entry_speed_sqr-exit_speed_sqr));
|
|
if (intersect_distance > 0.0) {
|
|
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
|
|
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;
|
|
} else {
|
|
// Full-trapezoid or acceleration-cruise types
|
|
prep.accelerate_until -= inv_2_accel*(pl_block->nominal_speed_sqr-pl_block->entry_speed_sqr);
|
|
}
|
|
} else { // Triangle type
|
|
prep.accelerate_until = intersect_distance;
|
|
prep.decelerate_after = intersect_distance;
|
|
prep.maximum_speed = sqrt(2.0*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 = 0.0;
|
|
// prep.decelerate_after = 0.0;
|
|
prep.maximum_speed = prep.exit_speed;
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
// 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. 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 = 0.0; // 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 (minimum_mm < 0.0) { minimum_mm = 0.0; }
|
|
|
|
do {
|
|
switch (prep.ramp_type) {
|
|
case RAMP_ACCEL:
|
|
// NOTE: Acceleration ramp only computes during first do-while loop.
|
|
speed_var = pl_block->acceleration*time_var;
|
|
mm_remaining -= time_var*(prep.current_speed + 0.5*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 = 2.0*(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 += speed_var;
|
|
}
|
|
break;
|
|
case RAMP_CRUISE:
|
|
// NOTE: mm_var used to retain the last mm_remaining for incomplete segment time_var calculations.
|
|
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.
|
|
speed_var = pl_block->acceleration*time_var; // Used as delta speed (mm/min)
|
|
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 - 0.5*speed_var); // (mm)
|
|
if (mm_var > prep.mm_complete) { // Deceleration only.
|
|
mm_remaining = mm_var;
|
|
prep.current_speed -= speed_var;
|
|
break; // Segment complete. Exit switch-case statement. Continue do-while loop.
|
|
}
|
|
} // End of block or end of forced-deceleration.
|
|
time_var = 2.0*(mm_remaining-prep.mm_complete)/(prep.current_speed+prep.exit_speed);
|
|
mm_remaining = prep.mm_complete;
|
|
}
|
|
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.
|
|
|
|
|
|
/* -----------------------------------------------------------------------------------
|
|
Compute segment step rate, steps to execute, and apply necessary rate corrections.
|
|
NOTE: Steps are computed by direct scalar conversion of the millimeter distance
|
|
remaining in the block, rather than incrementally tallying the steps executed per
|
|
segment. This helps in removing floating point round-off issues of several additions.
|
|
However, since floats have only 7.2 significant digits, long moves with extremely
|
|
high step counts can exceed the precision of floats, which can lead to lost steps.
|
|
Fortunately, this scenario is highly unlikely and unrealistic in CNC machines
|
|
supported by Grbl (i.e. exceeding 10 meters axis travel at 200 step/mm).
|
|
*/
|
|
float steps_remaining = prep.step_per_mm*mm_remaining; // Convert mm_remaining to steps
|
|
float n_steps_remaining = ceil(steps_remaining); // Round-up current steps remaining
|
|
float last_n_steps_remaining = ceil(prep.steps_remaining); // Round-up last steps remaining
|
|
prep_segment->n_step = last_n_steps_remaining-n_steps_remaining; // Compute number of steps to execute.
|
|
|
|
// Bail if we are at the end of a feed hold and don't have a step to execute.
|
|
if (prep_segment->n_step == 0) {
|
|
if (sys.state == STATE_HOLD) {
|
|
|
|
// Less than one step to decelerate to zero speed, but already very close. AMASS
|
|
// requires full steps to execute. So, just bail.
|
|
prep.current_speed = 0.0;
|
|
prep.dt_remainder = 0.0;
|
|
prep.steps_remaining = n_steps_remaining;
|
|
pl_block->millimeters = prep.steps_remaining/prep.step_per_mm; // Update with full steps.
|
|
plan_cycle_reinitialize();
|
|
sys.state = STATE_QUEUED;
|
|
return; // Segment not generated, but current step data still retained.
|
|
}
|
|
}
|
|
|
|
// Compute segment step rate. Since steps are integers and mm distances traveled are not,
|
|
// the end of every segment can have a partial step of varying magnitudes that are not
|
|
// executed, because the stepper ISR requires whole steps due to the AMASS algorithm. To
|
|
// compensate, we track the time to execute the previous segment's partial step and simply
|
|
// apply it with the partial step distance to the current segment, so that it minutely
|
|
// adjusts the whole segment rate to keep step output exact. These rate adjustments are
|
|
// typically very small and do not adversely effect performance, but ensures that Grbl
|
|
// outputs the exact acceleration and velocity profiles as computed by the planner.
|
|
dt += prep.dt_remainder; // Apply previous segment partial step execute time
|
|
float inv_rate = dt/(last_n_steps_remaining - steps_remaining); // Compute adjusted step rate inverse
|
|
prep.dt_remainder = (n_steps_remaining - steps_remaining)*inv_rate; // Update segment partial step time
|
|
|
|
// Compute CPU cycles per step for the prepped segment.
|
|
uint32_t cycles = ceil( (TICKS_PER_MICROSECOND*1000000*60)*inv_rate ); // (cycles/step)
|
|
|
|
#ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
|
|
// Compute step timing and multi-axis smoothing level.
|
|
// NOTE: AMASS overdrives the timer with each level, so only one prescalar is required.
|
|
if (cycles < AMASS_LEVEL1) { prep_segment->amass_level = 0; }
|
|
else {
|
|
if (cycles < AMASS_LEVEL2) { prep_segment->amass_level = 1; }
|
|
else if (cycles < AMASS_LEVEL3) { prep_segment->amass_level = 2; }
|
|
else { prep_segment->amass_level = 3; }
|
|
cycles >>= prep_segment->amass_level;
|
|
prep_segment->n_step <<= prep_segment->amass_level;
|
|
}
|
|
if (cycles < (1UL << 16)) { prep_segment->cycles_per_tick = cycles; } // < 65536 (4.1ms @ 16MHz)
|
|
else { prep_segment->cycles_per_tick = 0xffff; } // Just set the slowest speed possible.
|
|
#else
|
|
// Compute step timing and timer prescalar for normal step generation.
|
|
if (cycles < (1UL << 16)) { // < 65536 (4.1ms @ 16MHz)
|
|
prep_segment->prescaler = 1; // prescaler: 0
|
|
prep_segment->cycles_per_tick = cycles;
|
|
} else if (cycles < (1UL << 19)) { // < 524288 (32.8ms@16MHz)
|
|
prep_segment->prescaler = 2; // prescaler: 8
|
|
prep_segment->cycles_per_tick = cycles >> 3;
|
|
} else {
|
|
prep_segment->prescaler = 3; // prescaler: 64
|
|
if (cycles < (1UL << 22)) { // < 4194304 (262ms@16MHz)
|
|
prep_segment->cycles_per_tick = cycles >> 6;
|
|
} else { // Just set the slowest speed possible. (Around 4 step/sec.)
|
|
prep_segment->cycles_per_tick = 0xffff;
|
|
}
|
|
}
|
|
#endif
|
|
|
|
// Segment complete! Increment segment buffer indices.
|
|
segment_buffer_head = segment_next_head;
|
|
if ( ++segment_next_head == SEGMENT_BUFFER_SIZE ) { segment_next_head = 0; }
|
|
|
|
// Setup initial conditions for next segment.
|
|
if (mm_remaining > prep.mm_complete) {
|
|
// Normal operation. Block incomplete. Distance remaining in block to be executed.
|
|
pl_block->millimeters = mm_remaining;
|
|
prep.steps_remaining = steps_remaining;
|
|
} else {
|
|
// End of planner block or forced-termination. No more distance to be executed.
|
|
if (mm_remaining > 0.0) { // At end of forced-termination.
|
|
// Reset prep parameters for resuming and then bail.
|
|
// NOTE: Currently only feed holds qualify for this scenario. May change with overrides.
|
|
prep.current_speed = 0.0;
|
|
prep.dt_remainder = 0.0;
|
|
prep.steps_remaining = ceil(steps_remaining);
|
|
pl_block->millimeters = prep.steps_remaining/prep.step_per_mm; // Update with full steps.
|
|
plan_cycle_reinitialize();
|
|
sys.state = STATE_QUEUED; // End cycle.
|
|
|
|
return; // Bail!
|
|
// TODO: Try to move QUEUED setting into cycle re-initialize.
|
|
|
|
} else { // End of planner block
|
|
// The planner block is complete. All steps are set to be executed in the segment buffer.
|
|
pl_block = NULL;
|
|
plan_discard_current_block();
|
|
}
|
|
}
|
|
|
|
// int32_t blength = segment_buffer_head - segment_buffer_tail;
|
|
// if (blength < 0) { blength += SEGMENT_BUFFER_SIZE; }
|
|
// printInteger(blength);
|
|
}
|
|
}
|
|
|
|
/*
|
|
TODO: With feedrate overrides, increases to the override value will not significantly
|
|
change the current planner and stepper 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.
|
|
One "easy" way to do this is to have the step segment buffer enforce a deceleration and
|
|
continually re-plan the planner buffer until the plan becomes feasible. This can work
|
|
and may be easy to implement, but it expends a lot of CPU cycles and may block out the
|
|
rest of the functions from operating at peak efficiency. Still the question is how do
|
|
we know when the plan is feasible in the context of what's already in the code and not
|
|
require too much more code?
|
|
*/
|