Firmware/Marlin/stepper.cpp
2015-04-12 16:57:00 -07:00

1334 lines
40 KiB
C++

/*
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 "Marlin.h"
#include "stepper.h"
#include "planner.h"
#include "temperature.h"
#include "ultralcd.h"
#include "language.h"
#include "cardreader.h"
#include "speed_lookuptable.h"
#if HAS_DIGIPOTSS
#include <SPI.h>
#endif
//===========================================================================
//============================= public variables ============================
//===========================================================================
block_t *current_block; // A pointer to the block currently being traced
//===========================================================================
//============================= private variables ===========================
//===========================================================================
//static makes it impossible to be called from outside of this file by extern.!
// Variables used by The Stepper Driver Interrupt
static unsigned char out_bits; // The next stepping-bits to be output
static unsigned int cleaning_buffer_counter;
#ifdef Z_DUAL_ENDSTOPS
static bool performing_homing = false,
locked_z_motor = false,
locked_z2_motor = false;
#endif
// Counter variables for the bresenham line tracer
static long counter_x, counter_y, counter_z, counter_e;
volatile static unsigned long step_events_completed; // The number of step events executed in the current block
#ifdef ADVANCE
static long advance_rate, advance, final_advance = 0;
static long old_advance = 0;
static long e_steps[4];
#endif
static long acceleration_time, deceleration_time;
//static unsigned long accelerate_until, decelerate_after, acceleration_rate, initial_rate, final_rate, nominal_rate;
static unsigned short acc_step_rate; // needed for deccelaration start point
static char step_loops;
static unsigned short OCR1A_nominal;
static unsigned short step_loops_nominal;
volatile long endstops_trigsteps[3] = { 0 };
volatile long endstops_stepsTotal, endstops_stepsDone;
static volatile bool endstop_x_hit = false;
static volatile bool endstop_y_hit = false;
static volatile bool endstop_z_hit = false;
static volatile bool endstop_z_probe_hit = false; // Leaving this in even if Z_PROBE_ENDSTOP isn't defined, keeps code below cleaner. #ifdef it and usage below to save space.
#ifdef ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED
bool abort_on_endstop_hit = false;
#endif
#ifdef MOTOR_CURRENT_PWM_XY_PIN
int motor_current_setting[3] = DEFAULT_PWM_MOTOR_CURRENT;
#endif
#if HAS_X_MIN
static bool old_x_min_endstop = false;
#endif
#if HAS_X_MAX
static bool old_x_max_endstop = false;
#endif
#if HAS_Y_MIN
static bool old_y_min_endstop = false;
#endif
#if HAS_Y_MAX
static bool old_y_max_endstop = false;
#endif
#if HAS_Z_MIN
static bool old_z_min_endstop = false;
#endif
#if HAS_Z_MAX
static bool old_z_max_endstop = false;
#endif
#ifdef Z_DUAL_ENDSTOPS
// #if HAS_Z2_MIN
static bool old_z2_min_endstop = false;
// #endif
// #if HAS_Z2_MAX
static bool old_z2_max_endstop = false;
// #endif
#endif
#ifdef Z_PROBE_ENDSTOP // No need to check for valid pin, SanityCheck.h already does this.
static bool old_z_probe_endstop = false;
#endif
static bool check_endstops = true;
volatile long count_position[NUM_AXIS] = { 0 };
volatile signed char count_direction[NUM_AXIS] = { 1, 1, 1, 1 };
//===========================================================================
//================================ functions ================================
//===========================================================================
#ifdef DUAL_X_CARRIAGE
#define X_APPLY_DIR(v,ALWAYS) \
if (extruder_duplication_enabled || ALWAYS) { \
X_DIR_WRITE(v); \
X2_DIR_WRITE(v); \
} \
else { \
if (current_block->active_extruder) X2_DIR_WRITE(v); else X_DIR_WRITE(v); \
}
#define X_APPLY_STEP(v,ALWAYS) \
if (extruder_duplication_enabled || ALWAYS) { \
X_STEP_WRITE(v); \
X2_STEP_WRITE(v); \
} \
else { \
if (current_block->active_extruder != 0) X2_STEP_WRITE(v); else X_STEP_WRITE(v); \
}
#else
#define X_APPLY_DIR(v,Q) X_DIR_WRITE(v)
#define X_APPLY_STEP(v,Q) X_STEP_WRITE(v)
#endif
#ifdef Y_DUAL_STEPPER_DRIVERS
#define Y_APPLY_DIR(v,Q) { Y_DIR_WRITE(v); Y2_DIR_WRITE((v) != INVERT_Y2_VS_Y_DIR); }
#define Y_APPLY_STEP(v,Q) { Y_STEP_WRITE(v); Y2_STEP_WRITE(v); }
#else
#define Y_APPLY_DIR(v,Q) Y_DIR_WRITE(v)
#define Y_APPLY_STEP(v,Q) Y_STEP_WRITE(v)
#endif
#ifdef Z_DUAL_STEPPER_DRIVERS
#define Z_APPLY_DIR(v,Q) { Z_DIR_WRITE(v); Z2_DIR_WRITE(v); }
#ifdef Z_DUAL_ENDSTOPS
#define Z_APPLY_STEP(v,Q) \
if (performing_homing) { \
if (Z_HOME_DIR > 0) {\
if (!(old_z_max_endstop && (count_direction[Z_AXIS] > 0)) && !locked_z_motor) Z_STEP_WRITE(v); \
if (!(old_z2_max_endstop && (count_direction[Z_AXIS] > 0)) && !locked_z2_motor) Z2_STEP_WRITE(v); \
} else {\
if (!(old_z_min_endstop && (count_direction[Z_AXIS] < 0)) && !locked_z_motor) Z_STEP_WRITE(v); \
if (!(old_z2_min_endstop && (count_direction[Z_AXIS] < 0)) && !locked_z2_motor) Z2_STEP_WRITE(v); \
} \
} else { \
Z_STEP_WRITE(v); \
Z2_STEP_WRITE(v); \
}
#else
#define Z_APPLY_STEP(v,Q) { Z_STEP_WRITE(v); Z2_STEP_WRITE(v); }
#endif
#else
#define Z_APPLY_DIR(v,Q) Z_DIR_WRITE(v)
#define Z_APPLY_STEP(v,Q) Z_STEP_WRITE(v)
#endif
#define E_APPLY_STEP(v,Q) E_STEP_WRITE(v)
// intRes = intIn1 * intIn2 >> 16
// uses:
// r26 to store 0
// r27 to store the byte 1 of the 24 bit result
#define MultiU16X8toH16(intRes, charIn1, intIn2) \
asm volatile ( \
"clr r26 \n\t" \
"mul %A1, %B2 \n\t" \
"movw %A0, r0 \n\t" \
"mul %A1, %A2 \n\t" \
"add %A0, r1 \n\t" \
"adc %B0, r26 \n\t" \
"lsr r0 \n\t" \
"adc %A0, r26 \n\t" \
"adc %B0, r26 \n\t" \
"clr r1 \n\t" \
: \
"=&r" (intRes) \
: \
"d" (charIn1), \
"d" (intIn2) \
: \
"r26" \
)
// intRes = longIn1 * longIn2 >> 24
// uses:
// r26 to store 0
// r27 to store the byte 1 of the 48bit result
#define MultiU24X24toH16(intRes, longIn1, longIn2) \
asm volatile ( \
"clr r26 \n\t" \
"mul %A1, %B2 \n\t" \
"mov r27, r1 \n\t" \
"mul %B1, %C2 \n\t" \
"movw %A0, r0 \n\t" \
"mul %C1, %C2 \n\t" \
"add %B0, r0 \n\t" \
"mul %C1, %B2 \n\t" \
"add %A0, r0 \n\t" \
"adc %B0, r1 \n\t" \
"mul %A1, %C2 \n\t" \
"add r27, r0 \n\t" \
"adc %A0, r1 \n\t" \
"adc %B0, r26 \n\t" \
"mul %B1, %B2 \n\t" \
"add r27, r0 \n\t" \
"adc %A0, r1 \n\t" \
"adc %B0, r26 \n\t" \
"mul %C1, %A2 \n\t" \
"add r27, r0 \n\t" \
"adc %A0, r1 \n\t" \
"adc %B0, r26 \n\t" \
"mul %B1, %A2 \n\t" \
"add r27, r1 \n\t" \
"adc %A0, r26 \n\t" \
"adc %B0, r26 \n\t" \
"lsr r27 \n\t" \
"adc %A0, r26 \n\t" \
"adc %B0, r26 \n\t" \
"clr r1 \n\t" \
: \
"=&r" (intRes) \
: \
"d" (longIn1), \
"d" (longIn2) \
: \
"r26" , "r27" \
)
// Some useful constants
#define ENABLE_STEPPER_DRIVER_INTERRUPT() TIMSK1 |= BIT(OCIE1A)
#define DISABLE_STEPPER_DRIVER_INTERRUPT() TIMSK1 &= ~BIT(OCIE1A)
void endstops_hit_on_purpose() {
endstop_x_hit = endstop_y_hit = endstop_z_hit = endstop_z_probe_hit = false; // #ifdef endstop_z_probe_hit = to save space if needed.
}
void checkHitEndstops() {
if (endstop_x_hit || endstop_y_hit || endstop_z_hit || endstop_z_probe_hit) { // #ifdef || endstop_z_probe_hit to save space if needed.
SERIAL_ECHO_START;
SERIAL_ECHOPGM(MSG_ENDSTOPS_HIT);
if (endstop_x_hit) {
SERIAL_ECHOPAIR(" X:", (float)endstops_trigsteps[X_AXIS] / axis_steps_per_unit[X_AXIS]);
LCD_MESSAGEPGM(MSG_ENDSTOPS_HIT "X");
}
if (endstop_y_hit) {
SERIAL_ECHOPAIR(" Y:", (float)endstops_trigsteps[Y_AXIS] / axis_steps_per_unit[Y_AXIS]);
LCD_MESSAGEPGM(MSG_ENDSTOPS_HIT "Y");
}
if (endstop_z_hit) {
SERIAL_ECHOPAIR(" Z:", (float)endstops_trigsteps[Z_AXIS] / axis_steps_per_unit[Z_AXIS]);
LCD_MESSAGEPGM(MSG_ENDSTOPS_HIT "Z");
}
#ifdef Z_PROBE_ENDSTOP
if (endstop_z_probe_hit) {
SERIAL_ECHOPAIR(" Z_PROBE:", (float)endstops_trigsteps[Z_AXIS] / axis_steps_per_unit[Z_AXIS]);
LCD_MESSAGEPGM(MSG_ENDSTOPS_HIT "ZP");
}
#endif
SERIAL_EOL;
endstops_hit_on_purpose();
#if defined(ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED) && defined(SDSUPPORT)
if (abort_on_endstop_hit) {
card.sdprinting = false;
card.closefile();
quickStop();
setTargetHotend0(0);
setTargetHotend1(0);
setTargetHotend2(0);
setTargetHotend3(0);
setTargetBed(0);
}
#endif
}
}
void enable_endstops(bool check) { check_endstops = check; }
// __________________________
// /| |\ _________________ ^
// / | | \ /| |\ |
// / | | \ / | | \ 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
// 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 calculated with the leib ramp alghorithm.
void st_wake_up() {
// TCNT1 = 0;
ENABLE_STEPPER_DRIVER_INTERRUPT();
}
FORCE_INLINE unsigned short calc_timer(unsigned short step_rate) {
unsigned short timer;
if (step_rate > MAX_STEP_FREQUENCY) step_rate = MAX_STEP_FREQUENCY;
if (step_rate > 20000) { // If steprate > 20kHz >> step 4 times
step_rate = (step_rate >> 2) & 0x3fff;
step_loops = 4;
}
else if (step_rate > 10000) { // If steprate > 10kHz >> step 2 times
step_rate = (step_rate >> 1) & 0x7fff;
step_loops = 2;
}
else {
step_loops = 1;
}
if (step_rate < (F_CPU / 500000)) step_rate = (F_CPU / 500000);
step_rate -= (F_CPU / 500000); // Correct for minimal speed
if (step_rate >= (8 * 256)) { // higher step rate
unsigned short table_address = (unsigned short)&speed_lookuptable_fast[(unsigned char)(step_rate>>8)][0];
unsigned char tmp_step_rate = (step_rate & 0x00ff);
unsigned short gain = (unsigned short)pgm_read_word_near(table_address+2);
MultiU16X8toH16(timer, tmp_step_rate, gain);
timer = (unsigned short)pgm_read_word_near(table_address) - timer;
}
else { // lower step rates
unsigned short table_address = (unsigned short)&speed_lookuptable_slow[0][0];
table_address += ((step_rate)>>1) & 0xfffc;
timer = (unsigned short)pgm_read_word_near(table_address);
timer -= (((unsigned short)pgm_read_word_near(table_address+2) * (unsigned char)(step_rate & 0x0007))>>3);
}
if (timer < 100) { timer = 100; MYSERIAL.print(MSG_STEPPER_TOO_HIGH); MYSERIAL.println(step_rate); }//(20kHz this should never happen)
return timer;
}
// Initializes the trapezoid generator from the current block. Called whenever a new
// block begins.
FORCE_INLINE void trapezoid_generator_reset() {
#ifdef ADVANCE
advance = current_block->initial_advance;
final_advance = current_block->final_advance;
// Do E steps + advance steps
e_steps[current_block->active_extruder] += ((advance >>8) - old_advance);
old_advance = advance >>8;
#endif
deceleration_time = 0;
// step_rate to timer interval
OCR1A_nominal = calc_timer(current_block->nominal_rate);
// make a note of the number of step loops required at nominal speed
step_loops_nominal = step_loops;
acc_step_rate = current_block->initial_rate;
acceleration_time = calc_timer(acc_step_rate);
OCR1A = acceleration_time;
// SERIAL_ECHO_START;
// SERIAL_ECHOPGM("advance :");
// SERIAL_ECHO(current_block->advance/256.0);
// SERIAL_ECHOPGM("advance rate :");
// SERIAL_ECHO(current_block->advance_rate/256.0);
// SERIAL_ECHOPGM("initial advance :");
// SERIAL_ECHO(current_block->initial_advance/256.0);
// SERIAL_ECHOPGM("final advance :");
// SERIAL_ECHOLN(current_block->final_advance/256.0);
}
// "The Stepper Driver Interrupt" - This timer interrupt is the workhorse.
// It pops blocks from the block_buffer and executes them by pulsing the stepper pins appropriately.
ISR(TIMER1_COMPA_vect) {
if(cleaning_buffer_counter)
{
current_block = NULL;
plan_discard_current_block();
#ifdef SD_FINISHED_RELEASECOMMAND
if ((cleaning_buffer_counter == 1) && (SD_FINISHED_STEPPERRELEASE)) enquecommands_P(PSTR(SD_FINISHED_RELEASECOMMAND));
#endif
cleaning_buffer_counter--;
OCR1A = 200;
return;
}
// If there is no current block, attempt to pop one from the buffer
if (!current_block) {
// Anything in the buffer?
current_block = plan_get_current_block();
if (current_block) {
current_block->busy = true;
trapezoid_generator_reset();
counter_x = -(current_block->step_event_count >> 1);
counter_y = counter_z = counter_e = counter_x;
step_events_completed = 0;
#ifdef Z_LATE_ENABLE
if (current_block->steps[Z_AXIS] > 0) {
enable_z();
OCR1A = 2000; //1ms wait
return;
}
#endif
// #ifdef ADVANCE
// e_steps[current_block->active_extruder] = 0;
// #endif
}
else {
OCR1A = 2000; // 1kHz.
}
}
if (current_block != NULL) {
// Set directions TO DO This should be done once during init of trapezoid. Endstops -> interrupt
out_bits = current_block->direction_bits;
// Set the direction bits (X_AXIS=A_AXIS and Y_AXIS=B_AXIS for COREXY)
if (TEST(out_bits, X_AXIS)) {
X_APPLY_DIR(INVERT_X_DIR,0);
count_direction[X_AXIS] = -1;
}
else {
X_APPLY_DIR(!INVERT_X_DIR,0);
count_direction[X_AXIS] = 1;
}
if (TEST(out_bits, Y_AXIS)) {
Y_APPLY_DIR(INVERT_Y_DIR,0);
count_direction[Y_AXIS] = -1;
}
else {
Y_APPLY_DIR(!INVERT_Y_DIR,0);
count_direction[Y_AXIS] = 1;
}
#define UPDATE_ENDSTOP(axis,AXIS,minmax,MINMAX) \
bool axis ##_## minmax ##_endstop = (READ(AXIS ##_## MINMAX ##_PIN) != AXIS ##_## MINMAX ##_ENDSTOP_INVERTING); \
if (axis ##_## minmax ##_endstop && old_## axis ##_## minmax ##_endstop && (current_block->steps[AXIS ##_AXIS] > 0)) { \
endstops_trigsteps[AXIS ##_AXIS] = count_position[AXIS ##_AXIS]; \
endstop_## axis ##_hit = true; \
step_events_completed = current_block->step_event_count; \
} \
old_## axis ##_## minmax ##_endstop = axis ##_## minmax ##_endstop;
// Check X and Y endstops
if (check_endstops) {
#ifdef COREXY
// Head direction in -X axis for CoreXY bots.
// If DeltaX == -DeltaY, the movement is only in Y axis
if ((current_block->steps[A_AXIS] != current_block->steps[B_AXIS]) || (TEST(out_bits, A_AXIS) == TEST(out_bits, B_AXIS))) {
if (TEST(out_bits, X_HEAD))
#else
if (TEST(out_bits, X_AXIS)) // stepping along -X axis (regular cartesians bot)
#endif
{ // -direction
#ifdef DUAL_X_CARRIAGE
// with 2 x-carriages, endstops are only checked in the homing direction for the active extruder
if ((current_block->active_extruder == 0 && X_HOME_DIR == -1) || (current_block->active_extruder != 0 && X2_HOME_DIR == -1))
#endif
{
#if HAS_X_MIN
UPDATE_ENDSTOP(x, X, min, MIN);
#endif
}
}
else { // +direction
#ifdef DUAL_X_CARRIAGE
// with 2 x-carriages, endstops are only checked in the homing direction for the active extruder
if ((current_block->active_extruder == 0 && X_HOME_DIR == 1) || (current_block->active_extruder != 0 && X2_HOME_DIR == 1))
#endif
{
#if HAS_X_MAX
UPDATE_ENDSTOP(x, X, max, MAX);
#endif
}
}
#ifdef COREXY
}
// Head direction in -Y axis for CoreXY bots.
// If DeltaX == DeltaY, the movement is only in X axis
if ((current_block->steps[A_AXIS] != current_block->steps[B_AXIS]) || (TEST(out_bits, A_AXIS) != TEST(out_bits, B_AXIS))) {
if (TEST(out_bits, Y_HEAD))
#else
if (TEST(out_bits, Y_AXIS)) // -direction
#endif
{ // -direction
#if HAS_Y_MIN
UPDATE_ENDSTOP(y, Y, min, MIN);
#endif
}
else { // +direction
#if HAS_Y_MAX
UPDATE_ENDSTOP(y, Y, max, MAX);
#endif
}
#ifdef COREXY
}
#endif
}
if (TEST(out_bits, Z_AXIS)) { // -direction
Z_APPLY_DIR(INVERT_Z_DIR,0);
count_direction[Z_AXIS] = -1;
if (check_endstops) {
#if HAS_Z_MIN
#ifdef Z_DUAL_ENDSTOPS
bool z_min_endstop = READ(Z_MIN_PIN) != Z_MIN_ENDSTOP_INVERTING,
z2_min_endstop =
#if HAS_Z2_MIN
READ(Z2_MIN_PIN) != Z2_MIN_ENDSTOP_INVERTING
#else
z_min_endstop
#endif
;
bool z_min_both = z_min_endstop && old_z_min_endstop,
z2_min_both = z2_min_endstop && old_z2_min_endstop;
if ((z_min_both || z2_min_both) && current_block->steps[Z_AXIS] > 0) {
endstops_trigsteps[Z_AXIS] = count_position[Z_AXIS];
endstop_z_hit = true;
if (!performing_homing || (performing_homing && z_min_both && z2_min_both)) //if not performing home or if both endstops were trigged during homing...
step_events_completed = current_block->step_event_count;
}
old_z_min_endstop = z_min_endstop;
old_z2_min_endstop = z2_min_endstop;
#else // !Z_DUAL_ENDSTOPS
UPDATE_ENDSTOP(z, Z, min, MIN);
#endif // !Z_DUAL_ENDSTOPS
#endif // Z_MIN_PIN
#ifdef Z_PROBE_ENDSTOP
UPDATE_ENDSTOP(z, Z, probe, PROBE);
z_probe_endstop=(READ(Z_PROBE_PIN) != Z_PROBE_ENDSTOP_INVERTING);
if(z_probe_endstop && old_z_probe_endstop)
{
endstops_trigsteps[Z_AXIS] = count_position[Z_AXIS];
endstop_z_probe_hit=true;
// if (z_probe_endstop && old_z_probe_endstop) SERIAL_ECHOLN("z_probe_endstop = true");
}
old_z_probe_endstop = z_probe_endstop;
#endif
} // check_endstops
}
else { // +direction
Z_APPLY_DIR(!INVERT_Z_DIR,0);
count_direction[Z_AXIS] = 1;
if (check_endstops) {
#if HAS_Z_MAX
#ifdef Z_DUAL_ENDSTOPS
bool z_max_endstop = READ(Z_MAX_PIN) != Z_MAX_ENDSTOP_INVERTING,
z2_max_endstop =
#if HAS_Z2_MAX
READ(Z2_MAX_PIN) != Z2_MAX_ENDSTOP_INVERTING
#else
z_max_endstop
#endif
;
bool z_max_both = z_max_endstop && old_z_max_endstop,
z2_max_both = z2_max_endstop && old_z2_max_endstop;
if ((z_max_both || z2_max_both) && current_block->steps[Z_AXIS] > 0) {
endstops_trigsteps[Z_AXIS] = count_position[Z_AXIS];
endstop_z_hit = true;
// if (z_max_both) SERIAL_ECHOLN("z_max_endstop = true");
// if (z2_max_both) SERIAL_ECHOLN("z2_max_endstop = true");
if (!performing_homing || (performing_homing && z_max_both && z2_max_both)) //if not performing home or if both endstops were trigged during homing...
step_events_completed = current_block->step_event_count;
}
old_z_max_endstop = z_max_endstop;
old_z2_max_endstop = z2_max_endstop;
#else // !Z_DUAL_ENDSTOPS
UPDATE_ENDSTOP(z, Z, max, MAX);
#endif // !Z_DUAL_ENDSTOPS
#endif // Z_MAX_PIN
#ifdef Z_PROBE_ENDSTOP
UPDATE_ENDSTOP(z, Z, probe, PROBE);
z_probe_endstop=(READ(Z_PROBE_PIN) != Z_PROBE_ENDSTOP_INVERTING);
if(z_probe_endstop && old_z_probe_endstop)
{
endstops_trigsteps[Z_AXIS] = count_position[Z_AXIS];
endstop_z_probe_hit=true;
// if (z_probe_endstop && old_z_probe_endstop) SERIAL_ECHOLN("z_probe_endstop = true");
}
old_z_probe_endstop = z_probe_endstop;
#endif
} // check_endstops
} // +direction
#ifndef ADVANCE
if (TEST(out_bits, E_AXIS)) { // -direction
REV_E_DIR();
count_direction[E_AXIS] = -1;
}
else { // +direction
NORM_E_DIR();
count_direction[E_AXIS] = 1;
}
#endif //!ADVANCE
// Take multiple steps per interrupt (For high speed moves)
for (int8_t i = 0; i < step_loops; i++) {
#ifndef AT90USB
MSerial.checkRx(); // Check for serial chars.
#endif
#ifdef ADVANCE
counter_e += current_block->steps[E_AXIS];
if (counter_e > 0) {
counter_e -= current_block->step_event_count;
e_steps[current_block->active_extruder] += TEST(out_bits, E_AXIS) ? -1 : 1;
}
#endif //ADVANCE
#ifdef CONFIG_STEPPERS_TOSHIBA
/**
* The Toshiba stepper controller require much longer pulses.
* So we 'stage' decompose the pulses between high and low
* instead of doing each in turn. The extra tests add enough
* lag to allow it work with without needing NOPs
*/
#define STEP_ADD(axis, AXIS) \
counter_## axis += current_block->steps[AXIS ##_AXIS]; \
if (counter_## axis > 0) { AXIS ##_STEP_WRITE(HIGH); }
STEP_ADD(x,X);
STEP_ADD(y,Y);
STEP_ADD(z,Z);
#ifndef ADVANCE
STEP_ADD(e,E);
#endif
#define STEP_IF_COUNTER(axis, AXIS) \
if (counter_## axis > 0) { \
counter_## axis -= current_block->step_event_count; \
count_position[AXIS ##_AXIS] += count_direction[AXIS ##_AXIS]; \
AXIS ##_STEP_WRITE(LOW); \
}
STEP_IF_COUNTER(x, X);
STEP_IF_COUNTER(y, Y);
STEP_IF_COUNTER(z, Z);
#ifndef ADVANCE
STEP_IF_COUNTER(e, E);
#endif
#else // !CONFIG_STEPPERS_TOSHIBA
#define APPLY_MOVEMENT(axis, AXIS) \
counter_## axis += current_block->steps[AXIS ##_AXIS]; \
if (counter_## axis > 0) { \
AXIS ##_APPLY_STEP(!INVERT_## AXIS ##_STEP_PIN,0); \
counter_## axis -= current_block->step_event_count; \
count_position[AXIS ##_AXIS] += count_direction[AXIS ##_AXIS]; \
AXIS ##_APPLY_STEP(INVERT_## AXIS ##_STEP_PIN,0); \
}
APPLY_MOVEMENT(x, X);
APPLY_MOVEMENT(y, Y);
APPLY_MOVEMENT(z, Z);
#ifndef ADVANCE
APPLY_MOVEMENT(e, E);
#endif
#endif // CONFIG_STEPPERS_TOSHIBA
step_events_completed++;
if (step_events_completed >= current_block->step_event_count) break;
}
// Calculate new timer value
unsigned short timer;
unsigned short step_rate;
if (step_events_completed <= (unsigned long int)current_block->accelerate_until) {
MultiU24X24toH16(acc_step_rate, acceleration_time, current_block->acceleration_rate);
acc_step_rate += current_block->initial_rate;
// upper limit
if (acc_step_rate > current_block->nominal_rate)
acc_step_rate = current_block->nominal_rate;
// step_rate to timer interval
timer = calc_timer(acc_step_rate);
OCR1A = timer;
acceleration_time += timer;
#ifdef ADVANCE
for(int8_t i=0; i < step_loops; i++) {
advance += advance_rate;
}
//if (advance > current_block->advance) advance = current_block->advance;
// Do E steps + advance steps
e_steps[current_block->active_extruder] += ((advance >>8) - old_advance);
old_advance = advance >>8;
#endif
}
else if (step_events_completed > (unsigned long int)current_block->decelerate_after) {
MultiU24X24toH16(step_rate, deceleration_time, current_block->acceleration_rate);
if (step_rate > acc_step_rate) { // Check step_rate stays positive
step_rate = current_block->final_rate;
}
else {
step_rate = acc_step_rate - step_rate; // Decelerate from aceleration end point.
}
// lower limit
if (step_rate < current_block->final_rate)
step_rate = current_block->final_rate;
// step_rate to timer interval
timer = calc_timer(step_rate);
OCR1A = timer;
deceleration_time += timer;
#ifdef ADVANCE
for(int8_t i=0; i < step_loops; i++) {
advance -= advance_rate;
}
if (advance < final_advance) advance = final_advance;
// Do E steps + advance steps
e_steps[current_block->active_extruder] += ((advance >>8) - old_advance);
old_advance = advance >>8;
#endif //ADVANCE
}
else {
OCR1A = OCR1A_nominal;
// ensure we're running at the correct step rate, even if we just came off an acceleration
step_loops = step_loops_nominal;
}
// If current block is finished, reset pointer
if (step_events_completed >= current_block->step_event_count) {
current_block = NULL;
plan_discard_current_block();
}
}
}
#ifdef ADVANCE
unsigned char old_OCR0A;
// Timer interrupt for E. e_steps is set in the main routine;
// Timer 0 is shared with millies
ISR(TIMER0_COMPA_vect)
{
old_OCR0A += 52; // ~10kHz interrupt (250000 / 26 = 9615kHz)
OCR0A = old_OCR0A;
// Set E direction (Depends on E direction + advance)
for(unsigned char i=0; i<4;i++) {
if (e_steps[0] != 0) {
E0_STEP_WRITE(INVERT_E_STEP_PIN);
if (e_steps[0] < 0) {
E0_DIR_WRITE(INVERT_E0_DIR);
e_steps[0]++;
E0_STEP_WRITE(!INVERT_E_STEP_PIN);
}
else if (e_steps[0] > 0) {
E0_DIR_WRITE(!INVERT_E0_DIR);
e_steps[0]--;
E0_STEP_WRITE(!INVERT_E_STEP_PIN);
}
}
#if EXTRUDERS > 1
if (e_steps[1] != 0) {
E1_STEP_WRITE(INVERT_E_STEP_PIN);
if (e_steps[1] < 0) {
E1_DIR_WRITE(INVERT_E1_DIR);
e_steps[1]++;
E1_STEP_WRITE(!INVERT_E_STEP_PIN);
}
else if (e_steps[1] > 0) {
E1_DIR_WRITE(!INVERT_E1_DIR);
e_steps[1]--;
E1_STEP_WRITE(!INVERT_E_STEP_PIN);
}
}
#endif
#if EXTRUDERS > 2
if (e_steps[2] != 0) {
E2_STEP_WRITE(INVERT_E_STEP_PIN);
if (e_steps[2] < 0) {
E2_DIR_WRITE(INVERT_E2_DIR);
e_steps[2]++;
E2_STEP_WRITE(!INVERT_E_STEP_PIN);
}
else if (e_steps[2] > 0) {
E2_DIR_WRITE(!INVERT_E2_DIR);
e_steps[2]--;
E2_STEP_WRITE(!INVERT_E_STEP_PIN);
}
}
#endif
#if EXTRUDERS > 3
if (e_steps[3] != 0) {
E3_STEP_WRITE(INVERT_E_STEP_PIN);
if (e_steps[3] < 0) {
E3_DIR_WRITE(INVERT_E3_DIR);
e_steps[3]++;
E3_STEP_WRITE(!INVERT_E_STEP_PIN);
}
else if (e_steps[3] > 0) {
E3_DIR_WRITE(!INVERT_E3_DIR);
e_steps[3]--;
E3_STEP_WRITE(!INVERT_E_STEP_PIN);
}
}
#endif
}
}
#endif // ADVANCE
void st_init() {
digipot_init(); //Initialize Digipot Motor Current
microstep_init(); //Initialize Microstepping Pins
// initialise TMC Steppers
#ifdef HAVE_TMCDRIVER
tmc_init();
#endif
// initialise L6470 Steppers
#ifdef HAVE_L6470DRIVER
L6470_init();
#endif
// Initialize Dir Pins
#if HAS_X_DIR
X_DIR_INIT;
#endif
#if HAS_X2_DIR
X2_DIR_INIT;
#endif
#if HAS_Y_DIR
Y_DIR_INIT;
#if defined(Y_DUAL_STEPPER_DRIVERS) && HAS_Y2_DIR
Y2_DIR_INIT;
#endif
#endif
#if HAS_Z_DIR
Z_DIR_INIT;
#if defined(Z_DUAL_STEPPER_DRIVERS) && HAS_Z2_DIR
Z2_DIR_INIT;
#endif
#endif
#if HAS_E0_DIR
E0_DIR_INIT;
#endif
#if HAS_E1_DIR
E1_DIR_INIT;
#endif
#if HAS_E2_DIR
E2_DIR_INIT;
#endif
#if HAS_E3_DIR
E3_DIR_INIT;
#endif
//Initialize Enable Pins - steppers default to disabled.
#if HAS_X_ENABLE
X_ENABLE_INIT;
if (!X_ENABLE_ON) X_ENABLE_WRITE(HIGH);
#endif
#if HAS_X2_ENABLE
X2_ENABLE_INIT;
if (!X_ENABLE_ON) X2_ENABLE_WRITE(HIGH);
#endif
#if HAS_Y_ENABLE
Y_ENABLE_INIT;
if (!Y_ENABLE_ON) Y_ENABLE_WRITE(HIGH);
#if defined(Y_DUAL_STEPPER_DRIVERS) && HAS_Y2_ENABLE
Y2_ENABLE_INIT;
if (!Y_ENABLE_ON) Y2_ENABLE_WRITE(HIGH);
#endif
#endif
#if HAS_Z_ENABLE
Z_ENABLE_INIT;
if (!Z_ENABLE_ON) Z_ENABLE_WRITE(HIGH);
#if defined(Z_DUAL_STEPPER_DRIVERS) && HAS_Z2_ENABLE
Z2_ENABLE_INIT;
if (!Z_ENABLE_ON) Z2_ENABLE_WRITE(HIGH);
#endif
#endif
#if HAS_E0_ENABLE
E0_ENABLE_INIT;
if (!E_ENABLE_ON) E0_ENABLE_WRITE(HIGH);
#endif
#if HAS_E1_ENABLE
E1_ENABLE_INIT;
if (!E_ENABLE_ON) E1_ENABLE_WRITE(HIGH);
#endif
#if HAS_E2_ENABLE
E2_ENABLE_INIT;
if (!E_ENABLE_ON) E2_ENABLE_WRITE(HIGH);
#endif
#if HAS_E3_ENABLE
E3_ENABLE_INIT;
if (!E_ENABLE_ON) E3_ENABLE_WRITE(HIGH);
#endif
//endstops and pullups
#if HAS_X_MIN
SET_INPUT(X_MIN_PIN);
#ifdef ENDSTOPPULLUP_XMIN
WRITE(X_MIN_PIN,HIGH);
#endif
#endif
#if HAS_Y_MIN
SET_INPUT(Y_MIN_PIN);
#ifdef ENDSTOPPULLUP_YMIN
WRITE(Y_MIN_PIN,HIGH);
#endif
#endif
#if HAS_Z_MIN
SET_INPUT(Z_MIN_PIN);
#ifdef ENDSTOPPULLUP_ZMIN
WRITE(Z_MIN_PIN,HIGH);
#endif
#endif
#if HAS_X_MAX
SET_INPUT(X_MAX_PIN);
#ifdef ENDSTOPPULLUP_XMAX
WRITE(X_MAX_PIN,HIGH);
#endif
#endif
#if HAS_Y_MAX
SET_INPUT(Y_MAX_PIN);
#ifdef ENDSTOPPULLUP_YMAX
WRITE(Y_MAX_PIN,HIGH);
#endif
#endif
#if HAS_Z_MAX
SET_INPUT(Z_MAX_PIN);
#ifdef ENDSTOPPULLUP_ZMAX
WRITE(Z_MAX_PIN,HIGH);
#endif
#endif
#if HAS_Z2_MAX
SET_INPUT(Z2_MAX_PIN);
#ifdef ENDSTOPPULLUP_ZMAX
WRITE(Z2_MAX_PIN,HIGH);
#endif
#endif
#if (defined(Z_PROBE_PIN) && Z_PROBE_PIN >= 0) && defined(Z_PROBE_ENDSTOP) // Check for Z_PROBE_ENDSTOP so we don't pull a pin high unless it's to be used.
SET_INPUT(Z_PROBE_PIN);
#ifdef ENDSTOPPULLUP_ZPROBE
WRITE(Z_PROBE_PIN,HIGH);
#endif
#endif
#define AXIS_INIT(axis, AXIS, PIN) \
AXIS ##_STEP_INIT; \
AXIS ##_STEP_WRITE(INVERT_## PIN ##_STEP_PIN); \
disable_## axis()
#define E_AXIS_INIT(NUM) AXIS_INIT(e## NUM, E## NUM, E)
// Initialize Step Pins
#if HAS_X_STEP
AXIS_INIT(x, X, X);
#endif
#if HAS_X2_STEP
AXIS_INIT(x, X2, X);
#endif
#if HAS_Y_STEP
#if defined(Y_DUAL_STEPPER_DRIVERS) && HAS_Y2_STEP
Y2_STEP_INIT;
Y2_STEP_WRITE(INVERT_Y_STEP_PIN);
#endif
AXIS_INIT(y, Y, Y);
#endif
#if HAS_Z_STEP
#if defined(Z_DUAL_STEPPER_DRIVERS) && HAS_Z2_STEP
Z2_STEP_INIT;
Z2_STEP_WRITE(INVERT_Z_STEP_PIN);
#endif
AXIS_INIT(z, Z, Z);
#endif
#if HAS_E0_STEP
E_AXIS_INIT(0);
#endif
#if HAS_E1_STEP
E_AXIS_INIT(1);
#endif
#if HAS_E2_STEP
E_AXIS_INIT(2);
#endif
#if HAS_E3_STEP
E_AXIS_INIT(3);
#endif
// waveform generation = 0100 = CTC
TCCR1B &= ~BIT(WGM13);
TCCR1B |= BIT(WGM12);
TCCR1A &= ~BIT(WGM11);
TCCR1A &= ~BIT(WGM10);
// output mode = 00 (disconnected)
TCCR1A &= ~(3<<COM1A0);
TCCR1A &= ~(3<<COM1B0);
// Set the timer pre-scaler
// Generally we use a divider of 8, resulting in a 2MHz timer
// frequency on a 16MHz MCU. If you are going to change this, be
// sure to regenerate speed_lookuptable.h with
// create_speed_lookuptable.py
TCCR1B = (TCCR1B & ~(0x07<<CS10)) | (2<<CS10);
OCR1A = 0x4000;
TCNT1 = 0;
ENABLE_STEPPER_DRIVER_INTERRUPT();
#ifdef ADVANCE
#if defined(TCCR0A) && defined(WGM01)
TCCR0A &= ~BIT(WGM01);
TCCR0A &= ~BIT(WGM00);
#endif
e_steps[0] = e_steps[1] = e_steps[2] = e_steps[3] = 0;
TIMSK0 |= BIT(OCIE0A);
#endif //ADVANCE
enable_endstops(true); // Start with endstops active. After homing they can be disabled
sei();
}
// Block until all buffered steps are executed
void st_synchronize() {
while (blocks_queued()) {
manage_heater();
manage_inactivity();
lcd_update();
}
}
void st_set_position(const long &x, const long &y, const long &z, const long &e) {
CRITICAL_SECTION_START;
count_position[X_AXIS] = x;
count_position[Y_AXIS] = y;
count_position[Z_AXIS] = z;
count_position[E_AXIS] = e;
CRITICAL_SECTION_END;
}
void st_set_e_position(const long &e) {
CRITICAL_SECTION_START;
count_position[E_AXIS] = e;
CRITICAL_SECTION_END;
}
long st_get_position(uint8_t axis) {
long count_pos;
CRITICAL_SECTION_START;
count_pos = count_position[axis];
CRITICAL_SECTION_END;
return count_pos;
}
#ifdef ENABLE_AUTO_BED_LEVELING
float st_get_position_mm(uint8_t axis) {
float steper_position_in_steps = st_get_position(axis);
return steper_position_in_steps / axis_steps_per_unit[axis];
}
#endif // ENABLE_AUTO_BED_LEVELING
void finishAndDisableSteppers() {
st_synchronize();
disable_all_steppers();
}
void quickStop() {
cleaning_buffer_counter = 5000;
DISABLE_STEPPER_DRIVER_INTERRUPT();
while (blocks_queued()) plan_discard_current_block();
current_block = NULL;
ENABLE_STEPPER_DRIVER_INTERRUPT();
}
#ifdef BABYSTEPPING
// MUST ONLY BE CALLED BY AN ISR,
// No other ISR should ever interrupt this!
void babystep(const uint8_t axis, const bool direction) {
#define BABYSTEP_AXIS(axis, AXIS, INVERT) { \
enable_## axis(); \
uint8_t old_pin = AXIS ##_DIR_READ; \
AXIS ##_APPLY_DIR(INVERT_## AXIS ##_DIR^direction^INVERT, true); \
AXIS ##_APPLY_STEP(!INVERT_## AXIS ##_STEP_PIN, true); \
_delay_us(1U); \
AXIS ##_APPLY_STEP(INVERT_## AXIS ##_STEP_PIN, true); \
AXIS ##_APPLY_DIR(old_pin, true); \
}
switch(axis) {
case X_AXIS:
BABYSTEP_AXIS(x, X, false);
break;
case Y_AXIS:
BABYSTEP_AXIS(y, Y, false);
break;
case Z_AXIS: {
#ifndef DELTA
BABYSTEP_AXIS(z, Z, BABYSTEP_INVERT_Z);
#else // DELTA
bool z_direction = direction ^ BABYSTEP_INVERT_Z;
enable_x();
enable_y();
enable_z();
uint8_t old_x_dir_pin = X_DIR_READ,
old_y_dir_pin = Y_DIR_READ,
old_z_dir_pin = Z_DIR_READ;
//setup new step
X_DIR_WRITE(INVERT_X_DIR^z_direction);
Y_DIR_WRITE(INVERT_Y_DIR^z_direction);
Z_DIR_WRITE(INVERT_Z_DIR^z_direction);
//perform step
X_STEP_WRITE(!INVERT_X_STEP_PIN);
Y_STEP_WRITE(!INVERT_Y_STEP_PIN);
Z_STEP_WRITE(!INVERT_Z_STEP_PIN);
_delay_us(1U);
X_STEP_WRITE(INVERT_X_STEP_PIN);
Y_STEP_WRITE(INVERT_Y_STEP_PIN);
Z_STEP_WRITE(INVERT_Z_STEP_PIN);
//get old pin state back.
X_DIR_WRITE(old_x_dir_pin);
Y_DIR_WRITE(old_y_dir_pin);
Z_DIR_WRITE(old_z_dir_pin);
#endif
} break;
default: break;
}
}
#endif //BABYSTEPPING
// From Arduino DigitalPotControl example
void digitalPotWrite(int address, int value) {
#if HAS_DIGIPOTSS
digitalWrite(DIGIPOTSS_PIN,LOW); // take the SS pin low to select the chip
SPI.transfer(address); // send in the address and value via SPI:
SPI.transfer(value);
digitalWrite(DIGIPOTSS_PIN,HIGH); // take the SS pin high to de-select the chip:
//delay(10);
#endif
}
// Initialize Digipot Motor Current
void digipot_init() {
#if HAS_DIGIPOTSS
const uint8_t digipot_motor_current[] = DIGIPOT_MOTOR_CURRENT;
SPI.begin();
pinMode(DIGIPOTSS_PIN, OUTPUT);
for (int i = 0; i <= 4; i++) {
//digitalPotWrite(digipot_ch[i], digipot_motor_current[i]);
digipot_current(i,digipot_motor_current[i]);
}
#endif
#ifdef MOTOR_CURRENT_PWM_XY_PIN
pinMode(MOTOR_CURRENT_PWM_XY_PIN, OUTPUT);
pinMode(MOTOR_CURRENT_PWM_Z_PIN, OUTPUT);
pinMode(MOTOR_CURRENT_PWM_E_PIN, OUTPUT);
digipot_current(0, motor_current_setting[0]);
digipot_current(1, motor_current_setting[1]);
digipot_current(2, motor_current_setting[2]);
//Set timer5 to 31khz so the PWM of the motor power is as constant as possible. (removes a buzzing noise)
TCCR5B = (TCCR5B & ~(_BV(CS50) | _BV(CS51) | _BV(CS52))) | _BV(CS50);
#endif
}
void digipot_current(uint8_t driver, int current) {
#if HAS_DIGIPOTSS
const uint8_t digipot_ch[] = DIGIPOT_CHANNELS;
digitalPotWrite(digipot_ch[driver], current);
#endif
#ifdef MOTOR_CURRENT_PWM_XY_PIN
switch(driver) {
case 0: analogWrite(MOTOR_CURRENT_PWM_XY_PIN, 255L * current / MOTOR_CURRENT_PWM_RANGE); break;
case 1: analogWrite(MOTOR_CURRENT_PWM_Z_PIN, 255L * current / MOTOR_CURRENT_PWM_RANGE); break;
case 2: analogWrite(MOTOR_CURRENT_PWM_E_PIN, 255L * current / MOTOR_CURRENT_PWM_RANGE); break;
}
#endif
}
void microstep_init() {
#if HAS_MICROSTEPS_E1
pinMode(E1_MS1_PIN,OUTPUT);
pinMode(E1_MS2_PIN,OUTPUT);
#endif
#if HAS_MICROSTEPS
pinMode(X_MS1_PIN,OUTPUT);
pinMode(X_MS2_PIN,OUTPUT);
pinMode(Y_MS1_PIN,OUTPUT);
pinMode(Y_MS2_PIN,OUTPUT);
pinMode(Z_MS1_PIN,OUTPUT);
pinMode(Z_MS2_PIN,OUTPUT);
pinMode(E0_MS1_PIN,OUTPUT);
pinMode(E0_MS2_PIN,OUTPUT);
const uint8_t microstep_modes[] = MICROSTEP_MODES;
for (uint16_t i = 0; i < sizeof(microstep_modes) / sizeof(microstep_modes[0]); i++)
microstep_mode(i, microstep_modes[i]);
#endif
}
void microstep_ms(uint8_t driver, int8_t ms1, int8_t ms2) {
if (ms1 >= 0) switch(driver) {
case 0: digitalWrite(X_MS1_PIN, ms1); break;
case 1: digitalWrite(Y_MS1_PIN, ms1); break;
case 2: digitalWrite(Z_MS1_PIN, ms1); break;
case 3: digitalWrite(E0_MS1_PIN, ms1); break;
#if HAS_MICROSTEPS_E1
case 4: digitalWrite(E1_MS1_PIN, ms1); break;
#endif
}
if (ms2 >= 0) switch(driver) {
case 0: digitalWrite(X_MS2_PIN, ms2); break;
case 1: digitalWrite(Y_MS2_PIN, ms2); break;
case 2: digitalWrite(Z_MS2_PIN, ms2); break;
case 3: digitalWrite(E0_MS2_PIN, ms2); break;
#if defined(E1_MS2_PIN) && E1_MS2_PIN >= 0
case 4: digitalWrite(E1_MS2_PIN, ms2); break;
#endif
}
}
void microstep_mode(uint8_t driver, uint8_t stepping_mode) {
switch(stepping_mode) {
case 1: microstep_ms(driver,MICROSTEP1); break;
case 2: microstep_ms(driver,MICROSTEP2); break;
case 4: microstep_ms(driver,MICROSTEP4); break;
case 8: microstep_ms(driver,MICROSTEP8); break;
case 16: microstep_ms(driver,MICROSTEP16); break;
}
}
void microstep_readings() {
SERIAL_PROTOCOLPGM("MS1,MS2 Pins\n");
SERIAL_PROTOCOLPGM("X: ");
SERIAL_PROTOCOL(digitalRead(X_MS1_PIN));
SERIAL_PROTOCOLLN(digitalRead(X_MS2_PIN));
SERIAL_PROTOCOLPGM("Y: ");
SERIAL_PROTOCOL(digitalRead(Y_MS1_PIN));
SERIAL_PROTOCOLLN(digitalRead(Y_MS2_PIN));
SERIAL_PROTOCOLPGM("Z: ");
SERIAL_PROTOCOL(digitalRead(Z_MS1_PIN));
SERIAL_PROTOCOLLN(digitalRead(Z_MS2_PIN));
SERIAL_PROTOCOLPGM("E0: ");
SERIAL_PROTOCOL(digitalRead(E0_MS1_PIN));
SERIAL_PROTOCOLLN(digitalRead(E0_MS2_PIN));
#if HAS_MICROSTEPS_E1
SERIAL_PROTOCOLPGM("E1: ");
SERIAL_PROTOCOL(digitalRead(E1_MS1_PIN));
SERIAL_PROTOCOLLN(digitalRead(E1_MS2_PIN));
#endif
}
#ifdef Z_DUAL_ENDSTOPS
void In_Homing_Process(bool state) { performing_homing = state; }
void Lock_z_motor(bool state) { locked_z_motor = state; }
void Lock_z2_motor(bool state) { locked_z2_motor = state; }
#endif