plan_buffer_line

Hi everyone,

I was looking through the Marlin firmware and came across this function (plan_buffer_line) throughout marlin_main.cpp
It appears to be involved in the movement of the printer. I just cannot find this function anywhere in the files.
Does anyone know where this function is? I would like to figure out its inner workings and get to the bottom of this.

Thanks!

Bryan

This might be helpful:
[3digitalcooks.com]

You can find it in planner.cpp
It is a long function that generates the blocks according to many considerations such as speed and acceleration.

Here I copy the function for you:
#ifdef ENABLE_AUTO_BED_LEVELING
void plan_buffer_line(float x, float y, float z, const float &e, float feed_rate, const uint8_t &extruder)
#else
void plan_buffer_line(const float &x, const float &y, const float &z, const float &e, float feed_rate, const uint8_t &extruder)
#endif //ENABLE_AUTO_BED_LEVELING
{
// Calculate the buffer head after we push this byte
int next_buffer_head = next_block_index(block_buffer_head);

// If the buffer is full: good! That means we are well ahead of the robot.
// Rest here until there is room in the buffer.
while(block_buffer_tail == next_buffer_head)
{
manage_heater();
manage_inactivity();
lcd_update();
}

#ifdef ENABLE_AUTO_BED_LEVELING
apply_rotation_xyz(plan_bed_level_matrix, x, y, z);
#endif // ENABLE_AUTO_BED_LEVELING

// The target position of the tool in absolute steps
// Calculate target position in absolute steps
//this should be done after the wait, because otherwise a M92 code within the gcode disrupts this calculation somehow
long target[4];
target[X_AXIS] = lround(x*axis_steps_per_unit[X_AXIS]);
target[Y_AXIS] = lround(y*axis_steps_per_unit[Y_AXIS]);
target[Z_AXIS] = lround(z*axis_steps_per_unit[Z_AXIS]);
target[E_AXIS] = lround(e*axis_steps_per_unit[E_AXIS]);

#ifdef PREVENT_DANGEROUS_EXTRUDE
if(target[E_AXIS]!=position[E_AXIS])
{
if(degHotend(active_extruder)axis_steps_per_unit[E_AXIS]*EXTRUDE_MAXLENGTH)
{
position[E_AXIS]=target[E_AXIS]; //behave as if the move really took place, but ignore E part
SERIAL_ECHO_START;
SERIAL_ECHOLNPGM(MSG_ERR_LONG_EXTRUDE_STOP);
}
#endif
}
#endif

// Prepare to set up new block
block_t *block = &block_buffer[block_buffer_head];

// Mark block as not busy (Not executed by the stepper interrupt)
block->busy = false;

// Number of steps for each axis
#ifndef COREXY
// default non-h-bot planning
block->steps_x = labs(target[X_AXIS]-position[X_AXIS]);
block->steps_y = labs(target[Y_AXIS]-position[Y_AXIS]);
#else
// corexy planning
// these equations follow the form of the dA and dB equations on [www.corexy.com]
block->steps_x = labs((target[X_AXIS]-position[X_AXIS]) + (target[Y_AXIS]-position[Y_AXIS]));
block->steps_y = labs((target[X_AXIS]-position[X_AXIS]) - (target[Y_AXIS]-position[Y_AXIS]));
#endif
block->steps_z = labs(target[Z_AXIS]-position[Z_AXIS]);
block->steps_e = labs(target[E_AXIS]-position[E_AXIS]);
block->steps_e *= volumetric_multiplier[active_extruder];
block->steps_e *= extrudemultiply;
block->steps_e /= 100;
block->step_event_count = max(block->steps_x, max(block->steps_y, max(block->steps_z, block->steps_e)));

// Bail if this is a zero-length block
if (block->step_event_count <= dropsegments)
{
return;
}

block->fan_speed = fanSpeed;
#ifdef BARICUDA
block->valve_pressure = ValvePressure;
block->e_to_p_pressure = EtoPPressure;
#endif

// Compute direction bits for this block
block->direction_bits = 0;
#ifndef COREXY
if (target[X_AXIS] < position[X_AXIS])
{
block->direction_bits |= (1<direction_bits |= (1<direction_bits |= (1<direction_bits |= (1<direction_bits |= (1<direction_bits |= (1<active_extruder = extruder;

//enable active axes
#ifdef COREXY
if((block->steps_x != 0) || (block->steps_y != 0))
{
enable_x();
enable_y();
}
#else
if(block->steps_x != 0) enable_x();
if(block->steps_y != 0) enable_y();
#endif
#ifndef Z_LATE_ENABLE
if(block->steps_z != 0) enable_z();
#endif

// Enable extruder(s)
if(block->steps_e != 0)
{
if (DISABLE_INACTIVE_EXTRUDER) //enable only selected extruder
{

if(g_uc_extruder_last_move[0] > 0) g_uc_extruder_last_move[0]--;
if(g_uc_extruder_last_move[1] > 0) g_uc_extruder_last_move[1]--;
if(g_uc_extruder_last_move[2] > 0) g_uc_extruder_last_move[2]--;

switch(extruder)
{
case 0:
enable_e0();
g_uc_extruder_last_move[0] = BLOCK_BUFFER_SIZE*2;

if(g_uc_extruder_last_move[1] == 0) disable_e1();
if(g_uc_extruder_last_move[2] == 0) disable_e2();
break;
case 1:
enable_e1();
g_uc_extruder_last_move[1] = BLOCK_BUFFER_SIZE*2;

if(g_uc_extruder_last_move[0] == 0) disable_e0();
if(g_uc_extruder_last_move[2] == 0) disable_e2();
break;
case 2:
enable_e2();
g_uc_extruder_last_move[2] = BLOCK_BUFFER_SIZE*2;

if(g_uc_extruder_last_move[0] == 0) disable_e0();
if(g_uc_extruder_last_move[1] == 0) disable_e1();
break;
}
}
else //enable all
{
enable_e0();
enable_e1();
enable_e2();
}
}

if (block->steps_e == 0)
{
if(feed_ratesteps_x <=dropsegments && block->steps_y <=dropsegments && block->steps_z <=dropsegments )
{
block->millimeters = fabs(delta_mm[E_AXIS]);
}
else
{
#ifndef COREXY
block->millimeters = sqrt(square(delta_mm[X_AXIS]) + square(delta_mm[Y_AXIS]) + square(delta_mm[Z_AXIS]));
#else
block->millimeters = sqrt(square(delta_mm[X_HEAD]) + square(delta_mm[Y_HEAD]) + square(delta_mm[Z_AXIS]));
#endif
}
float inverse_millimeters = 1.0/block->millimeters; // Inverse millimeters to remove multiple divides

// Calculate speed in mm/second for each axis. No divide by zero due to previous checks.
float inverse_second = feed_rate * inverse_millimeters;

int moves_queued=(block_buffer_head-block_buffer_tail + BLOCK_BUFFER_SIZE) & (BLOCK_BUFFER_SIZE - 1);

// slow down when de buffer starts to empty, rather than wait at the corner for a buffer refill
#ifdef OLD_SLOWDOWN
if(moves_queued < (BLOCK_BUFFER_SIZE * 0.5) && moves_queued > 1)
feed_rate = feed_rate*moves_queued / (BLOCK_BUFFER_SIZE * 0.5);
#endif

#ifdef SLOWDOWN
// segment time im micro seconds
unsigned long segment_time = lround(1000000.0/inverse_second);
if ((moves_queued > 1) && (moves_queued < (BLOCK_BUFFER_SIZE * 0.5)))
{
if (segment_time < minsegmenttime)
{ // buffer is draining, add extra time. The amount of time added increases if the buffer is still emptied more.
inverse_second=1000000.0/(segment_time+lround(2*(minsegmenttime-segment_time)/moves_queued));
#ifdef XY_FREQUENCY_LIMIT
segment_time = lround(1000000.0/inverse_second);
#endif
}
}
#endif
// END OF SLOW DOWN SECTION


block->nominal_speed = block->millimeters * inverse_second; // (mm/sec) Always > 0
block->nominal_rate = ceil(block->step_event_count * inverse_second); // (step/sec) Always > 0

#ifdef FILAMENT_SENSOR
//FMM update ring buffer used for delay with filament measurements


if((extruder==FILAMENT_SENSOR_EXTRUDER_NUM) && (delay_index2 > -1)) //only for extruder with filament sensor and if ring buffer is initialized
{
delay_dist = delay_dist + delta_mm[E_AXIS]; //increment counter with next move in e axis

while (delay_dist >= (10*(MAX_MEASUREMENT_DELAY+1))) //check if counter is over max buffer size in mm
delay_dist = delay_dist - 10*(MAX_MEASUREMENT_DELAY+1); //loop around the buffer
while (delay_dist<0)
delay_dist = delay_dist + 10*(MAX_MEASUREMENT_DELAY+1); //loop around the buffer

delay_index1=delay_dist/10.0; //calculate index

//ensure the number is within range of the array after converting from floating point
if(delay_index1<0)
delay_index1=0;
else if (delay_index1>MAX_MEASUREMENT_DELAY)
delay_index1=MAX_MEASUREMENT_DELAY;

if(delay_index1 != delay_index2) //moved index
{
meas_sample=widthFil_to_size_ratio()-100; //subtract off 100 to reduce magnitude - to store in a signed char
}
while( delay_index1 != delay_index2)
{
delay_index2 = delay_index2 + 1;
if(delay_index2>MAX_MEASUREMENT_DELAY)
delay_index2=delay_index2-(MAX_MEASUREMENT_DELAY+1); //loop around buffer when incrementing
if(delay_index2<0)
delay_index2=0;
else if (delay_index2>MAX_MEASUREMENT_DELAY)
delay_index2=MAX_MEASUREMENT_DELAY;

measurement_delay[delay_index2]=meas_sample;
}


}
#endif


// Calculate and limit speed in mm/sec for each axis
float current_speed[4];
float speed_factor = 1.0; //factor <=1 do decrease speed
for(int i=0; i < 4; i++)
{
current_speed = delta_mm * inverse_second;
if(fabs(current_speed) > max_feedrate)
speed_factor = min(speed_factor, max_feedrate / fabs(current_speed));
}

// Max segement time in us.
#ifdef XY_FREQUENCY_LIMIT
#define MAX_FREQ_TIME (1000000.0/XY_FREQUENCY_LIMIT)
// Check and limit the xy direction change frequency
unsigned char direction_change = block->direction_bits ^ old_direction_bits;
old_direction_bits = block->direction_bits;
segment_time = lround((float)segment_time / speed_factor);

if((direction_change & (1<nominal_speed *= speed_factor;
block->nominal_rate *= speed_factor;
}

// Compute and limit the acceleration rate for the trapezoid generator.
float steps_per_mm = block->step_event_count/block->millimeters;
if(block->steps_x == 0 && block->steps_y == 0 && block->steps_z == 0)
{
block->acceleration_st = ceil(retract_acceleration * steps_per_mm); // convert to: acceleration steps/sec^2
}
else
{
block->acceleration_st = ceil(acceleration * steps_per_mm); // convert to: acceleration steps/sec^2
// Limit acceleration per axis
if(((float)block->acceleration_st * (float)block->steps_x / (float)block->step_event_count) > axis_steps_per_sqr_second[X_AXIS])
block->acceleration_st = axis_steps_per_sqr_second[X_AXIS];
if(((float)block->acceleration_st * (float)block->steps_y / (float)block->step_event_count) > axis_steps_per_sqr_second[Y_AXIS])
block->acceleration_st = axis_steps_per_sqr_second[Y_AXIS];
if(((float)block->acceleration_st * (float)block->steps_e / (float)block->step_event_count) > axis_steps_per_sqr_second[E_AXIS])
block->acceleration_st = axis_steps_per_sqr_second[E_AXIS];
if(((float)block->acceleration_st * (float)block->steps_z / (float)block->step_event_count ) > axis_steps_per_sqr_second[Z_AXIS])
block->acceleration_st = axis_steps_per_sqr_second[Z_AXIS];
}
block->acceleration = block->acceleration_st / steps_per_mm;
block->acceleration_rate = (long)((float)block->acceleration_st * (16777216.0 / (F_CPU / 8.0)));

#if 0 // Use old jerk for now
// Compute path unit vector
double unit_vec[3];

unit_vec[X_AXIS] = delta_mm[X_AXIS]*inverse_millimeters;
unit_vec[Y_AXIS] = delta_mm[Y_AXIS]*inverse_millimeters;
unit_vec[Z_AXIS] = delta_mm[Z_AXIS]*inverse_millimeters;

// Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
// Let a circle be tangent to both previous and current path line segments, where the junction
// deviation is defined as the distance from the junction to the closest edge of the circle,
// colinear with the circle center. The circular segment joining the two paths represents the
// path of centripetal acceleration. Solve for max velocity based on max acceleration about the
// radius of the circle, defined indirectly by junction deviation. This may be also viewed as
// path width or max_jerk in the previous grbl version. This approach does not actually deviate
// from path, but used as a robust way to compute cornering speeds, as it takes into account the
// nonlinearities of both the junction angle and junction velocity.
double vmax_junction = MINIMUM_PLANNER_SPEED; // Set default max junction speed

// Skip first block or when previous_nominal_speed is used as a flag for homing and offset cycles.
if ((block_buffer_head != block_buffer_tail) && (previous_nominal_speed > 0.0)) {
// Compute cosine of angle between previous and current path. (prev_unit_vec is negative)
// NOTE: Max junction velocity is computed without sin() or acos() by trig half angle identity.
double cos_theta = - previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
- previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
- previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS] ;

// Skip and use default max junction speed for 0 degree acute junction.
if (cos_theta < 0.95) {
vmax_junction = min(previous_nominal_speed,block->nominal_speed);
// Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
if (cos_theta > -0.95) {
// Compute maximum junction velocity based on maximum acceleration and junction deviation
double sin_theta_d2 = sqrt(0.5*(1.0-cos_theta)); // Trig half angle identity. Always positive.
vmax_junction = min(vmax_junction,
sqrt(block->acceleration * junction_deviation * sin_theta_d2/(1.0-sin_theta_d2)) );
}
}
}
#endif
// Start with a safe speed
float vmax_junction = max_xy_jerk/2;
float vmax_junction_factor = 1.0;
if(fabs(current_speed[Z_AXIS]) > max_z_jerk/2)
vmax_junction = min(vmax_junction, max_z_jerk/2);
if(fabs(current_speed[E_AXIS]) > max_e_jerk/2)
vmax_junction = min(vmax_junction, max_e_jerk/2);
vmax_junction = min(vmax_junction, block->nominal_speed);
float safe_speed = vmax_junction;

if ((moves_queued > 1) && (previous_nominal_speed > 0.0001)) {
float jerk = sqrt(pow((current_speed[X_AXIS]-previous_speed[X_AXIS]), 2)+pow((current_speed[Y_AXIS]-previous_speed[Y_AXIS]), 2));
// if((fabs(previous_speed[X_AXIS]) > 0.0001) || (fabs(previous_speed[Y_AXIS]) > 0.0001)) {
vmax_junction = block->nominal_speed;
// }
if (jerk > max_xy_jerk) {
vmax_junction_factor = (max_xy_jerk/jerk);
}
if(fabs(current_speed[Z_AXIS] - previous_speed[Z_AXIS]) > max_z_jerk) {
vmax_junction_factor= min(vmax_junction_factor, (max_z_jerk/fabs(current_speed[Z_AXIS] - previous_speed[Z_AXIS])));
}
if(fabs(current_speed[E_AXIS] - previous_speed[E_AXIS]) > max_e_jerk) {
vmax_junction_factor = min(vmax_junction_factor, (max_e_jerk/fabs(current_speed[E_AXIS] - previous_speed[E_AXIS])));
}
vmax_junction = min(previous_nominal_speed, vmax_junction * vmax_junction_factor); // Limit speed to max previous speed
}
block->max_entry_speed = vmax_junction;

// Initialize block entry speed. Compute based on deceleration to user-defined MINIMUM_PLANNER_SPEED.
double v_allowable = max_allowable_speed(-block->acceleration,MINIMUM_PLANNER_SPEED,block->millimeters);
block->entry_speed = min(vmax_junction, v_allowable);

// Initialize planner efficiency flags
// Set flag if block will always reach maximum junction speed regardless of entry/exit speeds.
// If a block can de/ac-celerate from nominal speed to zero within the length of the block, then
// the current block and next block junction speeds are guaranteed to always be at their maximum
// junction speeds in deceleration and acceleration, respectively. This is due to how the current
// block nominal speed limits both the current and next maximum junction speeds. Hence, in both
// the reverse and forward planners, the corresponding block junction speed will always be at the
// the maximum junction speed and may always be ignored for any speed reduction checks.
if (block->nominal_speed <= v_allowable) {
block->nominal_length_flag = true;
}
else {
block->nominal_length_flag = false;
}
block->recalculate_flag = true; // Always calculate trapezoid for new block

// Update previous path unit_vector and nominal speed
memcpy(previous_speed, current_speed, sizeof(previous_speed)); // previous_speed[] = current_speed[]
previous_nominal_speed = block->nominal_speed;


#ifdef ADVANCE
// Calculate advance rate
if((block->steps_e == 0) || (block->steps_x == 0 && block->steps_y == 0 && block->steps_z == 0)) {
block->advance_rate = 0;
block->advance = 0;
}
else {
long acc_dist = estimate_acceleration_distance(0, block->nominal_rate, block->acceleration_st);
float advance = (STEPS_PER_CUBIC_MM_E * EXTRUDER_ADVANCE_K) *
(current_speed[E_AXIS] * current_speed[E_AXIS] * EXTRUSION_AREA * EXTRUSION_AREA)*256;
block->advance = advance;
if(acc_dist == 0) {
block->advance_rate = 0;
}
else {
block->advance_rate = advance / (float)acc_dist;
}
}
/*
SERIAL_ECHO_START;
SERIAL_ECHOPGM("advance :");
SERIAL_ECHO(block->advance/256.0);
SERIAL_ECHOPGM("advance rate :");
SERIAL_ECHOLN(block->advance_rate/256.0);
*/
#endif // ADVANCE

calculate_trapezoid_for_block(block, block->entry_speed/block->nominal_speed,
safe_speed/block->nominal_speed);

// Move buffer head
block_buffer_head = next_buffer_head;

// Update position
memcpy(position, target, sizeof(target)); // position[] = target[]

planner_recalculate();

st_wake_up();
}

#ifdef ENABLE_AUTO_BED_LEVELING
vector_3 plan_get_position() {
vector_3 position = vector_3(st_get_position_mm(X_AXIS), st_get_position_mm(Y_AXIS), st_get_position_mm(Z_AXIS));

//position.debug("in plan_get position");
//plan_bed_level_matrix.debug("in plan_get bed_level");
matrix_3x3 inverse = matrix_3x3::transpose(plan_bed_level_matrix);
//inverse.debug("in plan_get inverse");
position.apply_rotation(inverse);
//position.debug("after rotation");

return position;
}