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first stab at replacing step-buffering with line-buffering

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Simen Svale Skogsrud
2010-03-02 21:46:51 +01:00
parent 36fd3a9bfb
commit 2be1f473cd
5 changed files with 2616 additions and 256 deletions
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186
motion_control.c
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@ -81,13 +81,7 @@ void compute_and_set_step_pace(double feed_rate, double millimeters_of_travel, u
void mc_line(double x, double y, double z, float feed_rate, int invert_feed_rate)
{
// Flags to keep track of which axes to step
uint8_t step_bits;
uint8_t axis; // loop variable
int8_t direction[3]; // The direction of travel along each axis (-1, 0 or 1)
int32_t target[3], // The target position in absolute steps
step_count[3], // Absolute steps of travel along each axis
counter[3], // A counter used in the bresenham algorithm for line plotting
maximum_steps; // The larges absolute step-count of any axis
int32_t target[3]; // The target position in absolute steps
// Setup ---------------------------------------------------------------------------------------------------
PORTD |= (1<<4);
@ -164,184 +158,6 @@ void mc_line(double x, double y, double z, float feed_rate, int invert_feed_rate
void mc_arc(double theta, double angular_travel, double radius, double linear_travel, int axis_1, int axis_2,
int axis_linear, double feed_rate, int invert_feed_rate)
{
uint32_t start_x, start_y; // The start position in the coordinate system local to the circle
uint32_t diagonal_error; // A variable to keep track of varations in the error-value during
// the tracing of the arc
int8_t direction[3]; // The direction of travel along each axis (-1, 0 or 1)
int8_t angular_direction; // 1 = clockwise, -1 = anticlockwise
int32_t x, y, target_x, target_y; // current position and target position in the
// local coordinate system of the arc-generator where [0,0] is the
// center of the arc.
int target_direction_x, target_direction_y; // signof(target_x)*angular_direction precalculated for speed
int32_t error; // error is always == (x**2 + y**2 - radius**2),
int dx, dy; // Trace directions
// Setup arc interpolation --------------------------------------------------------------------------------
uint32_t radius_steps = round(radius*X_STEPS_PER_MM);
if(radius_steps == 0) { return; }
// Determine angular direction (+1 = clockwise, -1 = counterclockwise)
angular_direction = signof(angular_travel);
// Calculate the initial position and target position in the local coordinate system of the arc
start_x = x = round(sin(theta)*radius_steps);
start_y = y = round(cos(theta)*radius_steps);
target_x = trunc(sin(theta+angular_travel)*radius_steps);
target_y = trunc(cos(theta+angular_travel)*radius_steps);
// Precalculate these values to optimize target detection
target_direction_x = signof(target_x)*angular_direction;
target_direction_y = signof(target_y)*angular_direction;
// The "error" factor is kept up to date so that it is always == (x**2+y**2-radius**2). When error
// <0 we are inside the arc, when it is >0 we are outside of the arc, and when it is 0 we
// are exactly on top of the arc.
error = x*x + y*y - radius_steps*radius_steps;
// Estimate length of arc in steps -------------------------------------------------------------------------
/*
To support helical motion we need to know in advance how many steppings the arc will need.
The calculations are based on the fact that we trace the circle by offsetting a square. The circle has
four "sides" or quadrants. For each quadrant we step mainly in one axis. The amount steps for one quarter of the
circle (e.g. along the x axis with positive y) is equal to one side of a square inscribed in the circle we
are tracing.
Quadrants of the circle
+---- 0 ----+ 0 - y is always positive and |x| < |y|
| | 1 - x is always positive and |x| > |y|
| | 2 - y is always negative and |x| < |y|
3 + 1 3 - x is always negative and |x| > |y|
| |
| | length of one side: 2*radius/sqrt(2)
+---- 2 ----+
*/
// Find the quadrants of the starting point and the target
int start_quadrant = quadrant_of_the_circle(start_x, start_y);
int target_quadrant = quadrant_of_the_circle(target_x, target_y);
uint32_t arc_steps=0;
// Will this whole arc take place within the same quadrant?
if (start_quadrant == target_quadrant && (fabs(angular_travel) <= (M_PI/2))) {
if(quadrant_horizontal(start_quadrant)) { // a horizontal quadrant where x will be the primary direction
arc_steps = labs(target_x-start_x);
} else { // a vertical quadrant where y will be the primary direction
arc_steps = labs(target_y-start_y);
}
} else { // the start and target points are in different quadrants
// Lets estimate the amount of steps along half a quadrant
uint32_t steps_in_half_quadrant = ceil(radius_steps/sqrt(2));
// Add the steps in the first partial quadrant
arc_steps += steps_in_partial_quadrant(start_x, start_y,
start_quadrant, angular_direction, steps_in_half_quadrant);
// Count the number of full quadrants between the start and end quadrants
uint8_t full_quadrants_traveled = full_quadrants_between(start_quadrant, target_quadrant, angular_direction);
// Add steps for the full quadrants plus some stray steps for "corners"
arc_steps += full_quadrants_traveled*(steps_in_half_quadrant*2+1);
// Add the steps in the final partial quadrant. By inverting the angular direction we get the correct number for
// the target quadrant which steps through the opposite part of the quadrant with respect to the start quadrant.
arc_steps += steps_in_partial_quadrant(target_x, target_y,
target_quadrant, -angular_direction, steps_in_half_quadrant);
}
// Set up the linear interpolation of the "depth" axis -----------------------------------------------------
int32_t linear_steps = labs(st_millimeters_to_steps(linear_travel, axis_linear));
int linear_direction = signof(linear_travel);
// The number of steppings needed to trace this motion is equal to the motion that require the maximum
// amount of steps: the arc or the line:
int32_t maximum_steps = max(linear_steps, arc_steps);
// Initialize the counters to do 2D linear bresenham as if the motion along the arc itself was a single axis
// of the line, while the linear "depth" axis was the other.
int32_t linear_counter = -maximum_steps/2;
int32_t arc_counter = -maximum_steps/2;
// Calculate feed rate -------------------------------------------------------------------------------------
// We then calculate the millimeters of helical travel
double millimeters_of_travel = hypot(angular_travel*radius, labs(linear_travel));
// Then we calculate the microseconds between each step as if we will trace the full circle.
// It doesn't matter what fraction of the circle we are actually going to trace. The pace is the same.
compute_and_set_step_pace(feed_rate, millimeters_of_travel, maximum_steps, invert_feed_rate);
// Execution -----------------------------------------------------------------------------------------------
mode = MC_MODE_ARC;
// Set the direction of the linear or "depth" axis, cause it will never change
direction[axis_linear] = linear_direction;
// Cache some stepper bit-masks to speed up the interpolation code
uint8_t axis_1_bit = st_bit_for_stepper(axis_1);
uint8_t axis_2_bit = st_bit_for_stepper(axis_2);
uint8_t axis_linear_bit = st_bit_for_stepper(axis_linear);
uint8_t diagonal_bits = (axis_1_bit | axis_2_bit);
uint8_t step_bits;
while(mode)
{
// This loop sets the bits in the step_bits variable for each stepper it wants to step in this cycle.
step_bits = 0;
// The bresenham algorithm chooses when to travel in the depth axis and when to travel along the arc
linear_counter += linear_steps;
if (linear_counter > 0) {
linear_counter -= maximum_steps;
// Move one step in the depth direction:
step_bits |= axis_linear_bit;
}
arc_counter += arc_steps;
if (arc_counter > 0) {
arc_counter -= maximum_steps;
// Do one step of the arc:
// Determine directions for each axis at this point in the arc
dx = (y!=0) ? signof(y) * angular_direction : -signof(x);
dy = (x!=0) ? -signof(x) * angular_direction : -signof(y);
// Take dx and dy which are local to the arc being generated and map them on to the
// selected tool-space-axes for the current arc.
direction[axis_1] = dx;
direction[axis_2] = dy;
// Check which axis will be "major" for this stepping
if (labs(x)<labs(y)) {
// X is major: Step arc horizontally
error += 1 + 2*x * dx;
x+=dx;
diagonal_error = error + 1 + 2*y*dy;
if(labs(error) >= labs(diagonal_error)) {
y += dy;
error = diagonal_error;
step_bits |= diagonal_bits; // step diagonal
} else {
step_bits |= axis_1_bit; // step straight
}
} else {
// Y is major: Step arc vertically
error += 1 + 2*y * dy;
y+=dy;
diagonal_error = error + 1 + 2*x * dx;
if(labs(error) >= labs(diagonal_error)) {
x += dx;
error = diagonal_error;
step_bits |= diagonal_bits; // step diagonal
} else {
step_bits |= axis_2_bit; // step straight
}
}
}
// Tell the steppers to do the stepping
set_stepper_directions(direction);
step_steppers(step_bits);
// Check if target has been reached. Todo: Simplify/optimize/clarify
if ((x * target_direction_y >=
target_x * target_direction_y) &&
(y * target_direction_x <=
target_y * target_direction_x))
{ if ((signof(x) == signof(target_x)) && (signof(y) == signof(target_y)))
{ mode = MC_MODE_AT_REST; } }
}
// Update the tool position to the new actual position
position[axis_1] += x-start_x;
position[axis_2] += y-start_y;
position[axis_2] += linear_steps*linear_direction;
}
void mc_go_home()