03e2ca7cd5
- ALPHA status. - Multitasking ability with run-time command executions for real-time control and feedback. - Decelerating feed hold and resume during operation. - System abort/reset, which immediately kills all movement and re-initializes grbl. - Re-structured grbl to easily allow for new features: Status reporting, jogging, backlash compensation. (To be completed in the following releases.) - Resized TX/RX serial buffers (32/128 bytes) - Increased planner buffer size to 20 blocks. - Updated documentation.
434 lines
19 KiB
C
434 lines
19 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) 2009-2011 Simen Svale Skogsrud
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Copyright (c) 2011 Sungeun K. Jeon
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Copyright (c) 2011 Jens Geisler
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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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/* The timer calculations of this module informed by the 'RepRap cartesian firmware' by Zack Smith
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and Philipp Tiefenbacher. */
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#include "stepper.h"
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#include "config.h"
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#include "settings.h"
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#include <math.h>
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#include <stdlib.h>
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#include <util/delay.h>
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#include "nuts_bolts.h"
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#include <avr/interrupt.h>
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#include "planner.h"
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#include "limits.h"
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#include "print.h"
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// Some useful constants
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#define STEP_MASK ((1<<X_STEP_BIT)|(1<<Y_STEP_BIT)|(1<<Z_STEP_BIT)) // All step bits
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#define DIRECTION_MASK ((1<<X_DIRECTION_BIT)|(1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT)) // All direction bits
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#define STEPPING_MASK (STEP_MASK | DIRECTION_MASK) // All stepping-related bits (step/direction)
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#define TICKS_PER_MICROSECOND (F_CPU/1000000)
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#define CYCLES_PER_ACCELERATION_TICK ((TICKS_PER_MICROSECOND*1000000)/ACCELERATION_TICKS_PER_SECOND)
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// Stepper state variable. Contains running data and trapezoid variables.
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typedef struct {
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volatile uint8_t cycle_start; // Cycle start flag
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volatile uint8_t feed_hold; // Feed hold flag
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// Used by the bresenham line algorithm
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int32_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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uint32_t event_count;
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uint32_t step_events_completed; // The number of step events left in current motion
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// Used by the trapezoid generator
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uint32_t cycles_per_step_event; // The number of machine cycles between each step event
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uint32_t trapezoid_tick_cycle_counter; // The cycles since last trapezoid_tick. Used to generate ticks at a steady
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// pace without allocating a separate timer
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uint32_t trapezoid_adjusted_rate; // The current rate of step_events according to the trapezoid generator
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uint32_t min_safe_rate; // Minimum safe rate for full deceleration rate reduction step. Otherwise halves step_rate.
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} stepper_state_t;
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static stepper_state_t st;
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static int32_t st_position[3]; // Track current position in steps from initialization state.
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static block_t *current_block; // A pointer to the block currently being traced
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// Used by the stepper driver interrupt
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static uint8_t step_pulse_time; // Step pulse reset time after step rise
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static uint8_t out_bits; // The next stepping-bits to be output
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static volatile uint8_t busy; // True when SIG_OUTPUT_COMPARE1A is being serviced. Used to avoid retriggering that handler.
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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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//
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// time ----->
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//
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// The trapezoid is the shape the speed curve over time. It starts at block->initial_rate, accelerates by block->rate_delta
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// during the first block->accelerate_until step_events_completed, then keeps going at constant speed until
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// step_events_completed reaches block->decelerate_after after which it decelerates until the trapezoid generator is reset.
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// The slope of acceleration is always +/- block->rate_delta and is applied at a constant rate following the midpoint rule
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// by the trapezoid generator, which is called ACCELERATION_TICKS_PER_SECOND times per second.
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static void set_step_events_per_minute(uint32_t steps_per_minute);
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// Stepper state initialization
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static void st_wake_up()
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{
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// Initialize stepper output bits
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out_bits = (0) ^ (settings.invert_mask);
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// Set step pulse time. Ad hoc computation from oscilloscope.
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step_pulse_time = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND) >> 3);
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// Enable steppers by resetting the stepper disable port
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STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT);
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// Enable stepper driver interrupt
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TIMSK1 |= (1<<OCIE1A);
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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
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TIMSK1 &= ~(1<<OCIE1A);
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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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#if STEPPER_IDLE_LOCK_TIME
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_delay_ms(STEPPER_IDLE_LOCK_TIME);
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#endif
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// Disable steppers by setting stepper disable
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STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
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}
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// This function determines an acceleration velocity change every CYCLES_PER_ACCELERATION_TICK by
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// keeping track of the number of elapsed cycles during a de/ac-celeration. The code assumes that
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// step_events occur significantly more often than the acceleration velocity iterations.
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static uint8_t iterate_trapezoid_cycle_counter()
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{
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st.trapezoid_tick_cycle_counter += st.cycles_per_step_event;
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if(st.trapezoid_tick_cycle_counter > CYCLES_PER_ACCELERATION_TICK) {
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st.trapezoid_tick_cycle_counter -= CYCLES_PER_ACCELERATION_TICK;
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return(true);
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} else {
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return(false);
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}
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}
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// "The Stepper Driver Interrupt" - This timer interrupt is the workhorse of Grbl. It is executed at the rate set with
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// config_step_timer. It pops blocks from the block_buffer and executes them by pulsing the stepper pins appropriately.
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// It is supported by The Stepper Port Reset Interrupt which it uses to reset the stepper port after each pulse.
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// The bresenham line tracer algorithm controls all three stepper outputs simultaneously with these two interrupts.
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// NOTE: ISR_NOBLOCK allows SIG_OVERFLOW2 to trigger on-time regardless of time in this handler.
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// TODO: ISR_NOBLOCK is the same as the old SIGNAL with sei() method, but is optimizable by the compiler. On
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// an oscilloscope there is a weird hitch in the step pulse during high load operation. Very infrequent, but
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// when this does happen most of the time the pulse falling edge is randomly delayed by 20%-50% of the total
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// intended pulse time, but sometimes it pulses less than 3usec. The former likely caused by the serial
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// interrupt doing its thing, not that big of a deal, but the latter cause is unknown and worrisome. Need
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// to track down what is causing this problem. Functionally, this shouldn't cause any noticeable issues
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// as long as stepper drivers have a pulse minimum of 1usec or so (Pololu and any Allegro IC are ok).
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ISR(TIMER1_COMPA_vect,ISR_NOBLOCK)
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{
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if (busy) { return; } // The busy-flag is used to avoid reentering this interrupt
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busy = true;
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// Set the direction pins a couple of nanoseconds before we step the steppers
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STEPPING_PORT = (STEPPING_PORT & ~DIRECTION_MASK) | (out_bits & DIRECTION_MASK);
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// Then pulse the stepping pins
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STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | out_bits;
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// Reset 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.
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TCNT2 = step_pulse_time;
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// If there is no current block, attempt to pop one from the buffer
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if (current_block == NULL) {
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// Anything in the buffer? If so, initialize next motion.
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current_block = plan_get_current_block();
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if (current_block != NULL) {
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if (!st.feed_hold) { // During feed hold, do not update rate and trap counter. Keep decelerating.
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st.trapezoid_adjusted_rate = current_block->initial_rate;
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set_step_events_per_minute(st.trapezoid_adjusted_rate); // Initialize cycles_per_step_event
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st.trapezoid_tick_cycle_counter = CYCLES_PER_ACCELERATION_TICK/2; // Start halfway for midpoint rule.
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}
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st.min_safe_rate = current_block->rate_delta + (current_block->rate_delta >> 1); // 1.5 x rate_delta
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st.counter_x = -(current_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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st.event_count = current_block->step_event_count;
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st.step_events_completed = 0;
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} else {
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st.cycle_start = false;
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st.feed_hold = false;
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st_go_idle();
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}
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}
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if (current_block != NULL) {
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// Execute step displacement profile by bresenham line algorithm
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out_bits = current_block->direction_bits;
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st.counter_x += current_block->steps_x;
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if (st.counter_x > 0) {
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out_bits |= (1<<X_STEP_BIT);
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st.counter_x -= st.event_count;
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if (out_bits & (1<<X_DIRECTION_BIT)) { st_position[X_AXIS]--; }
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else { st_position[X_AXIS]++; }
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}
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st.counter_y += current_block->steps_y;
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if (st.counter_y > 0) {
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out_bits |= (1<<Y_STEP_BIT);
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st.counter_y -= st.event_count;
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if (out_bits & (1<<Y_DIRECTION_BIT)) { st_position[Y_AXIS]--; }
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else { st_position[Y_AXIS]++; }
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}
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st.counter_z += current_block->steps_z;
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if (st.counter_z > 0) {
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out_bits |= (1<<Z_STEP_BIT);
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st.counter_z -= st.event_count;
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if (out_bits & (1<<Z_DIRECTION_BIT)) { st_position[Z_AXIS]--; }
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else { st_position[Z_AXIS]++; }
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}
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st.step_events_completed++; // Iterate step events
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// While in block steps, check for de/ac-celeration events and execute them accordingly.
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if (st.step_events_completed < current_block->step_event_count) {
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if (st.feed_hold) {
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// Check for and execute feed hold by enforcing a steady deceleration from the moment of
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// execution. The rate of deceleration is limited by rate_delta and will never decelerate
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// faster or slower than in normal operation. If the distance required for the feed hold
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// deceleration spans more than one block, the initial rate of the following blocks are not
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// updated and deceleration is continued according to their corresponding rate_delta.
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// NOTE: The trapezoid tick cycle counter is not updated intentionally. This ensures that
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// the deceleration is smooth regardless of where the feed hold is initiated and if the
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// deceleration distance spans multiple blocks.
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if ( iterate_trapezoid_cycle_counter() ) {
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// If deceleration complete, set system flags and shutdown steppers.
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if (st.trapezoid_adjusted_rate <= current_block->rate_delta) {
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// Just go idle. Do not NULL current block. The bresenham algorithm variables must
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// remain intact to ensure the stepper path is exactly the same.
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st.cycle_start = false;
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st_go_idle();
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sys_state |= BIT_REPLAN_CYCLE; // Flag main program that feed hold is complete.
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} else {
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st.trapezoid_adjusted_rate -= current_block->rate_delta;
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set_step_events_per_minute(st.trapezoid_adjusted_rate);
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}
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}
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} else {
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// The trapezoid generator always checks step event location to ensure de/ac-celerations are
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// executed and terminated at exactly the right time. This helps prevent over/under-shooting
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// the target position and speed.
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// NOTE: By increasing the ACCELERATION_TICKS_PER_SECOND in config.h, the resolution of the
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// discrete velocity changes increase and accuracy can increase as well to a point. Numerical
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// round-off errors can effect this, if set too high. This is important to note if a user has
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// very high acceleration and/or feedrate requirements for their machine.
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if (st.step_events_completed < current_block->accelerate_until) {
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// Iterate cycle counter and check if speeds need to be increased.
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if ( iterate_trapezoid_cycle_counter() ) {
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st.trapezoid_adjusted_rate += current_block->rate_delta;
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if (st.trapezoid_adjusted_rate >= current_block->nominal_rate) {
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// Reached nominal rate a little early. Cruise at nominal rate until decelerate_after.
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st.trapezoid_adjusted_rate = current_block->nominal_rate;
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}
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set_step_events_per_minute(st.trapezoid_adjusted_rate);
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}
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} else if (st.step_events_completed >= current_block->decelerate_after) {
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// Reset trapezoid tick cycle counter to make sure that the deceleration is performed the
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// same every time. Reset to CYCLES_PER_ACCELERATION_TICK/2 to follow the midpoint rule for
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// an accurate approximation of the deceleration curve.
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if (st.step_events_completed == current_block-> decelerate_after) {
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st.trapezoid_tick_cycle_counter = CYCLES_PER_ACCELERATION_TICK/2;
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} else {
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// Iterate cycle counter and check if speeds need to be reduced.
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if ( iterate_trapezoid_cycle_counter() ) {
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// NOTE: We will only do a full speed reduction if the result is more than the minimum safe
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// rate, initialized in trapezoid reset as 1.5 x rate_delta. Otherwise, reduce the speed by
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// half increments until finished. The half increments are guaranteed not to exceed the
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// CNC acceleration limits, because they will never be greater than rate_delta. This catches
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// small errors that might leave steps hanging after the last trapezoid tick or a very slow
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// step rate at the end of a full stop deceleration in certain situations. The half rate
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// reductions should only be called once or twice per block and create a nice smooth
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// end deceleration.
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if (st.trapezoid_adjusted_rate > st.min_safe_rate) {
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st.trapezoid_adjusted_rate -= current_block->rate_delta;
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} else {
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st.trapezoid_adjusted_rate >>= 1; // Bit shift divide by 2
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}
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if (st.trapezoid_adjusted_rate < current_block->final_rate) {
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// Reached final rate a little early. Cruise to end of block at final rate.
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st.trapezoid_adjusted_rate = current_block->final_rate;
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}
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set_step_events_per_minute(st.trapezoid_adjusted_rate);
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}
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}
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} else {
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// No accelerations. Make sure we cruise exactly at the nominal rate.
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if (st.trapezoid_adjusted_rate != current_block->nominal_rate) {
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st.trapezoid_adjusted_rate = current_block->nominal_rate;
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set_step_events_per_minute(st.trapezoid_adjusted_rate);
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}
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}
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}
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} else {
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// If current block is finished, reset pointer
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current_block = NULL;
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plan_discard_current_block();
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}
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}
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out_bits ^= settings.invert_mask; // Apply stepper invert mask
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busy = false;
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}
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// This interrupt is set up by SIG_OUTPUT_COMPARE1A when it sets the motor port bits. It resets
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// the motor port after a short period (settings.pulse_microseconds) completing one step cycle.
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ISR(TIMER2_OVF_vect)
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{
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// Reset stepping pins (leave the direction pins)
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STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | (settings.invert_mask & STEP_MASK);
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}
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// Reset and clear stepper subsystem variables
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void st_reset()
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{
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memset(&st, 0, sizeof(st));
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set_step_events_per_minute(MINIMUM_STEPS_PER_MINUTE);
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current_block = NULL;
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busy = false;
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}
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// Initialize and start the stepper motor subsystem
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void st_init()
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{
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// Configure directions of interface pins
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STEPPING_DDR |= STEPPING_MASK;
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STEPPING_PORT = (STEPPING_PORT & ~STEPPING_MASK) | settings.invert_mask;
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STEPPERS_DISABLE_DDR |= 1<<STEPPERS_DISABLE_BIT;
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// waveform generation = 0100 = CTC
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TCCR1B &= ~(1<<WGM13);
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TCCR1B |= (1<<WGM12);
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TCCR1A &= ~(1<<WGM11);
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TCCR1A &= ~(1<<WGM10);
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// output mode = 00 (disconnected)
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TCCR1A &= ~(3<<COM1A0);
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TCCR1A &= ~(3<<COM1B0);
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// Configure Timer 2
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TCCR2A = 0; // Normal operation
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TCCR2B = (1<<CS21); // Full speed, 1/8 prescaler
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TIMSK2 |= (1<<TOIE2);
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// Initialize machine position vector
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clear_vector(st_position);
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// Start in the idle state
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st_go_idle();
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}
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// Configures the prescaler and ceiling of timer 1 to produce the given rate as accurately as possible.
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// Returns the actual number of cycles per interrupt
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static uint32_t config_step_timer(uint32_t cycles)
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{
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uint16_t ceiling;
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uint16_t prescaler;
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uint32_t actual_cycles;
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if (cycles <= 0xffffL) {
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ceiling = cycles;
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prescaler = 0; // prescaler: 0
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actual_cycles = ceiling;
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} else if (cycles <= 0x7ffffL) {
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ceiling = cycles >> 3;
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prescaler = 1; // prescaler: 8
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actual_cycles = ceiling * 8L;
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} else if (cycles <= 0x3fffffL) {
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ceiling = cycles >> 6;
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prescaler = 2; // prescaler: 64
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actual_cycles = ceiling * 64L;
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} else if (cycles <= 0xffffffL) {
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ceiling = (cycles >> 8);
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prescaler = 3; // prescaler: 256
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actual_cycles = ceiling * 256L;
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} else if (cycles <= 0x3ffffffL) {
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ceiling = (cycles >> 10);
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prescaler = 4; // prescaler: 1024
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actual_cycles = ceiling * 1024L;
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} else {
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// Okay, that was slower than we actually go. Just set the slowest speed
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ceiling = 0xffff;
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prescaler = 4;
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actual_cycles = 0xffff * 1024;
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}
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// Set prescaler
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TCCR1B = (TCCR1B & ~(0x07<<CS10)) | ((prescaler+1)<<CS10);
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// Set ceiling
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OCR1A = ceiling;
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return(actual_cycles);
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}
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static void set_step_events_per_minute(uint32_t steps_per_minute)
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{
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if (steps_per_minute < MINIMUM_STEPS_PER_MINUTE) { steps_per_minute = MINIMUM_STEPS_PER_MINUTE; }
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st.cycles_per_step_event = config_step_timer((TICKS_PER_MICROSECOND*1000000*60)/steps_per_minute);
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}
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// Planner external interface to start stepper interrupt and execute the blocks in queue. Called
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// by planner auto-start and run-time command functions.
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void st_cycle_start()
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{
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if (!st.cycle_start) {
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if (!st.feed_hold) {
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st.cycle_start = true;
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st_wake_up();
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}
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}
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}
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// Execute a feed hold with deceleration, only during cycle. Called by main program.
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void st_feed_hold()
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{
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if (!st.feed_hold) {
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if (st.cycle_start) {
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st.feed_hold = true;
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}
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}
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}
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// Reinitializes the cycle plan and stepper system after a feed hold for a resume. Called by
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// runtime command execution in the main program, ensuring that the planner re-plans safely.
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// NOTE: Bresenham algorithm variables are still maintained through both the planner and stepper
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// cycle reinitializations. The stepper path should continue exactly as if nothing has happened.
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// Only the planner de/ac-celerations profiles and stepper rates have been updated.
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void st_cycle_reinitialize()
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{
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// Replan buffer from the feed hold stop location.
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plan_cycle_reinitialize(current_block->step_event_count - st.step_events_completed);
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// Update initial rate and timers after feed hold.
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st.trapezoid_adjusted_rate = 0; // Resumes from rest
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set_step_events_per_minute(st.trapezoid_adjusted_rate);
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st.trapezoid_tick_cycle_counter = CYCLES_PER_ACCELERATION_TICK/2; // Start halfway for midpoint rule.
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st.step_events_completed = 0;
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st.feed_hold = false; // Release feed hold. Cycle is ready to re-start.
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}
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