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/*
stepper.c - stepper motor driver: executes motion plans using stepper motors
Part of Grbl
Copyright (c) 2009-2011 Simen Svale Skogsrud
Grbl is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Grbl is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with Grbl. If not, see <http://www.gnu.org/licenses/>.
*/
/* The timer calculations of this module informed by the 'RepRap cartesian firmware' by Zack Smith
and Philipp Tiefenbacher. */
#include "stepper.h"
#include "config.h"
#include "settings.h"
#include <math.h>
#include <stdlib.h>
#include <util/delay.h>
#include "nuts_bolts.h"
#include <avr/interrupt.h>
#include "planner.h"
#include "wiring_serial.h"
#include <avr/pgmspace.h>
// Some useful constants
#define STEP_MASK ((1<<X_STEP_BIT)|(1<<Y_STEP_BIT)|(1<<Z_STEP_BIT)) // All step bits
#define DIRECTION_MASK ((1<<X_DIRECTION_BIT)|(1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT)) // All direction bits
#define STEPPING_MASK (STEP_MASK | DIRECTION_MASK) // All stepping-related bits (step/direction)
//#define LIMIT_MASK ((1<<X_LIMIT_BIT)|(1<<Y_LIMIT_BIT)|(1<<Z_LIMIT_BIT)) // All limit bits
#define TICKS_PER_MICROSECOND (F_CPU/1000000)
#define CYCLES_PER_ACCELERATION_TICK ((TICKS_PER_MICROSECOND*1000000)/ACCELERATION_TICKS_PER_SECOND)
#define MINIMUM_STEPS_PER_MINUTE 1200 // The stepper subsystem will never run slower than this, exept when sleeping
#define ENABLE_STEPPER_DRIVER_INTERRUPT() TIMSK1 |= (1<<OCIE1A)
#define DISABLE_STEPPER_DRIVER_INTERRUPT() TIMSK1 &= ~(1<<OCIE1A)
static block_t *current_block; // A pointer to the block currently being traced
// Variables used by The Stepper Driver Interrupt
static uint8_t out_bits; // The next stepping-bits to be output
static int32_t counter_x, // Counter variables for the bresenham line tracer
counter_y,
counter_z;
static uint32_t step_events_completed; // The number of step events executed in the current block
static volatile int busy; // TRUE when SIG_OUTPUT_COMPARE1A is being serviced. Used to avoid retriggering that handler.
// Variables used by the trapezoid generation
static uint32_t cycles_per_step_event; // The number of machine cycles between each step event
static uint32_t trapezoid_tick_cycle_counter; // The cycles since last trapezoid_tick. Used to generate ticks at a steady
// pace without allocating a separate timer
static uint32_t trapezoid_adjusted_rate; // The current rate of step_events according to the trapezoid generator
// __________________________
// /| |\ _________________ ^
// / | | \ /| |\ |
// / | | \ / | | \ s
// / | | | | | \ p
// / | | | | | \ e
// +-----+------------------------+---+--+---------------+----+ e
// | BLOCK 1 | BLOCK 2 | d
//
// time ----->
//
// The trapezoid is the shape the speed curve over time. It starts at block->initial_rate, accelerates by block->rate_delta
// during the first block->accelerate_until step_events_completed, then keeps going at constant speed until
// step_events_completed reaches block->decelerate_after after which it decelerates until the trapezoid generator is reset.
// The slope of acceleration is always +/- block->rate_delta and is applied at a constant rate by trapezoid_generator_tick()
// that is called ACCELERATION_TICKS_PER_SECOND times per second.
void set_step_events_per_minute(uint32_t steps_per_minute);
void st_wake_up() {
ENABLE_STEPPER_DRIVER_INTERRUPT();
}
// Initializes the trapezoid generator from the current block. Called whenever a new
// block begins.
inline void trapezoid_generator_reset() {
trapezoid_adjusted_rate = current_block->initial_rate;
trapezoid_tick_cycle_counter = 0; // Always start a new trapezoid with a full acceleration tick
set_step_events_per_minute(trapezoid_adjusted_rate);
}
// This is called ACCELERATION_TICKS_PER_SECOND times per second by the step_event
// interrupt. It can be assumed that the trapezoid-generator-parameters and the
// current_block stays untouched by outside handlers for the duration of this function call.
inline void trapezoid_generator_tick() {
if (current_block) {
if (step_events_completed < current_block->accelerate_until) {
trapezoid_adjusted_rate += current_block->rate_delta;
set_step_events_per_minute(trapezoid_adjusted_rate);
} else if (step_events_completed > current_block->decelerate_after) {
// NOTE: We will only reduce speed if the result will be > 0. This catches small
// rounding errors that might leave steps hanging after the last trapezoid tick.
if (trapezoid_adjusted_rate > current_block->rate_delta) {
trapezoid_adjusted_rate -= current_block->rate_delta;
}
if (trapezoid_adjusted_rate < current_block->final_rate) {
trapezoid_adjusted_rate = current_block->final_rate;
}
set_step_events_per_minute(trapezoid_adjusted_rate);
} else {
// Make sure we cruise at exactly nominal rate
if (trapezoid_adjusted_rate != current_block->nominal_rate) {
trapezoid_adjusted_rate = current_block->nominal_rate;
set_step_events_per_minute(trapezoid_adjusted_rate);
}
}
}
}
// "The Stepper Driver Interrupt" - This timer interrupt is the workhorse of Grbl. It is executed at the rate set with
// config_step_timer. It pops blocks from the block_buffer and executes them by pulsing the stepper pins appropriately.
// It is supported by The Stepper Port Reset Interrupt which it uses to reset the stepper port after each pulse.
SIGNAL(TIMER1_COMPA_vect)
{
// TODO: Check if the busy-flag can be eliminated by just disableing this interrupt while we are in it
if(busy){ return; } // The busy-flag is used to avoid reentering this interrupt
// Set the direction pins a cuple of nanoseconds before we step the steppers
STEPPING_PORT = (STEPPING_PORT & ~DIRECTION_MASK) | (out_bits & DIRECTION_MASK);
// Then pulse the stepping pins
STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | out_bits;
// Reset step pulse reset timer so that The Stepper Port Reset Interrupt can reset the signal after
// exactly settings.pulse_microseconds microseconds.
TCNT2 = -(((settings.pulse_microseconds-2)*TICKS_PER_MICROSECOND)/8);
busy = TRUE;
sei(); // Re enable interrupts (normally disabled while inside an interrupt handler)
// ((We re-enable interrupts in order for SIG_OVERFLOW2 to be able to be triggered
// at exactly the right time even if we occasionally spend a lot of time inside this handler.))
// If there is no current block, attempt to pop one from the buffer
if (current_block == NULL) {
// Anything in the buffer?
current_block = plan_get_current_block();
if (current_block != NULL) {
trapezoid_generator_reset();
counter_x = -(current_block->step_event_count >> 1);
counter_y = counter_x;
counter_z = counter_x;
step_events_completed = 0;
} else {
DISABLE_STEPPER_DRIVER_INTERRUPT();
}
}
if (current_block != NULL) {
out_bits = current_block->direction_bits;
counter_x += current_block->steps_x;
if (counter_x > 0) {
out_bits |= (1<<X_STEP_BIT);
counter_x -= current_block->step_event_count;
}
counter_y += current_block->steps_y;
if (counter_y > 0) {
out_bits |= (1<<Y_STEP_BIT);
counter_y -= current_block->step_event_count;
}
counter_z += current_block->steps_z;
if (counter_z > 0) {
out_bits |= (1<<Z_STEP_BIT);
counter_z -= current_block->step_event_count;
}
// If current block is finished, reset pointer
step_events_completed += 1;
if (step_events_completed >= current_block->step_event_count) {
current_block = NULL;
plan_discard_current_block();
}
} else {
out_bits = 0;
}
out_bits ^= settings.invert_mask;
// In average this generates a trapezoid_generator_tick every CYCLES_PER_ACCELERATION_TICK by keeping track
// of the number of elapsed cycles. The code assumes that step_events occur significantly more often than
// trapezoid_generator_ticks as they well should.
trapezoid_tick_cycle_counter += cycles_per_step_event;
if(trapezoid_tick_cycle_counter > CYCLES_PER_ACCELERATION_TICK) {
trapezoid_tick_cycle_counter -= CYCLES_PER_ACCELERATION_TICK;
trapezoid_generator_tick();
}
busy=FALSE;
}
// This interrupt is set up by SIG_OUTPUT_COMPARE1A when it sets the motor port bits. It resets
// the motor port after a short period (settings.pulse_microseconds) completing one step cycle.
SIGNAL(TIMER2_OVF_vect)
{
// reset stepping pins (leave the direction pins)
STEPPING_PORT = (STEPPING_PORT & ~STEP_MASK) | (settings.invert_mask & STEP_MASK);
}
// Initialize and start the stepper motor subsystem
void st_init()
{
// Configure directions of interface pins
STEPPING_DDR |= STEPPING_MASK;
STEPPING_PORT = (STEPPING_PORT & ~STEPPING_MASK) | settings.invert_mask;
//LIMIT_DDR &= ~(LIMIT_MASK);
STEPPERS_ENABLE_DDR |= 1<<STEPPERS_ENABLE_BIT;
STEPPERS_RESET_DDR |= 1<<STEPPERS_RESET_BIT;
// waveform generation = 0100 = CTC
TCCR1B &= ~(1<<WGM13);
TCCR1B |= (1<<WGM12);
TCCR1A &= ~(1<<WGM11);
TCCR1A &= ~(1<<WGM10);
// output mode = 00 (disconnected)
TCCR1A &= ~(3<<COM1A0);
TCCR1A &= ~(3<<COM1B0);
// Configure Timer 2
TCCR2A = 0; // Normal operation
TCCR2B = (1<<CS21); // Full speed, 1/8 prescaler
TIMSK2 |= (1<<TOIE2);
set_step_events_per_minute(6000);
DISABLE_STEPPER_DRIVER_INTERRUPT();
trapezoid_tick_cycle_counter = 0;
// set enable pin
//STEPPERS_ENABLE_PORT |= 1<<STEPPERS_ENABLE_BIT;
STEPPERS_ENABLE_PORT |= 0<<STEPPERS_ENABLE_BIT;
STEPPERS_RESET_PORT |= 1<<STEPPERS_RESET_BIT;
sei();
}
// Block until all buffered steps are executed
void st_synchronize()
{
while(plan_get_current_block()) { sleep_mode(); }
}
// Configures the prescaler and ceiling of timer 1 to produce the given rate as accurately as possible.
// Returns the actual number of cycles per interrupt
uint32_t config_step_timer(uint32_t cycles)
{
uint16_t ceiling;
uint16_t prescaler;
uint32_t actual_cycles;
if (cycles <= 0xffffL) {
ceiling = cycles;
prescaler = 0; // prescaler: 0
actual_cycles = ceiling;
} else if (cycles <= 0x7ffffL) {
ceiling = cycles >> 3;
prescaler = 1; // prescaler: 8
actual_cycles = ceiling * 8L;
} else if (cycles <= 0x3fffffL) {
ceiling = cycles >> 6;
prescaler = 2; // prescaler: 64
actual_cycles = ceiling * 64L;
} else if (cycles <= 0xffffffL) {
ceiling = (cycles >> 8);
prescaler = 3; // prescaler: 256
actual_cycles = ceiling * 256L;
} else if (cycles <= 0x3ffffffL) {
ceiling = (cycles >> 10);
prescaler = 4; // prescaler: 1024
actual_cycles = ceiling * 1024L;
} else {
// Okay, that was slower than we actually go. Just set the slowest speed
ceiling = 0xffff;
prescaler = 4;
actual_cycles = 0xffff * 1024;
}
// Set prescaler
TCCR1B = (TCCR1B & ~(0x07<<CS10)) | ((prescaler+1)<<CS10);
// Set ceiling
OCR1A = ceiling;
return(actual_cycles);
}
void set_step_events_per_minute(uint32_t steps_per_minute) {
if (steps_per_minute < MINIMUM_STEPS_PER_MINUTE) { steps_per_minute = MINIMUM_STEPS_PER_MINUTE; }
cycles_per_step_event = config_step_timer((TICKS_PER_MICROSECOND*1000000*60)/steps_per_minute);
}
void st_go_home()
{
// Todo: Perform the homing cycle
}