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motion_control.c - high level interface for issuing motion commands
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
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 <>.
#include <avr/io.h>
#include "settings.h"
#include "motion_control.h"
#include <util/delay.h>
#include <math.h>
#include <stdlib.h>
#include "nuts_bolts.h"
#include "stepper.h"
#include "planner.h"
#include "wiring_serial.h"
void mc_dwell(uint32_t milliseconds)
// Execute an arc. theta == start angle, angular_travel == number of radians to go along the arc,
// positive angular_travel means clockwise, negative means counterclockwise. Radius == the radius of the
// circle in millimeters. axis_1 and axis_2 selects the circle plane in tool space. Stick the remaining
// axis in axis_l which will be the axis for linear travel if you are tracing a helical motion.
// position is a pointer to a vector representing the current position in millimeters.
#ifdef __AVR_ATmega328P__
// The arc is approximated by generating a huge number of tiny, linear segments. The length of each
// segment is configured in settings.mm_per_arc_segment.
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, double *position)
int acceleration_manager_was_enabled = plan_is_acceleration_manager_enabled();
plan_set_acceleration_manager_enabled(FALSE); // disable acceleration management for the duration of the arc
double millimeters_of_travel = hypot(angular_travel*radius, labs(linear_travel));
if (millimeters_of_travel == 0.0) { return; }
uint16_t segments = ceil(millimeters_of_travel/settings.mm_per_arc_segment);
// Multiply inverse feed_rate to compensate for the fact that this movement is approximated
// by a number of discrete segments. The inverse feed_rate should be correct for the sum of
// all segments.
if (invert_feed_rate) { feed_rate *= segments; }
// The angular motion for each segment
double theta_per_segment = angular_travel/segments;
// The linear motion for each segment
double linear_per_segment = linear_travel/segments;
// Compute the center of this circle
double center_x = position[axis_1]-sin(theta)*radius;
double center_y = position[axis_2]-cos(theta)*radius;
// a vector to track the end point of each segment
double target[3];
int i;
// Initialize the linear axis
target[axis_linear] = position[axis_linear];
for (i=0; i<=segments; i++) {
target[axis_linear] += linear_per_segment;
theta += theta_per_segment;
target[axis_1] = center_x+sin(theta)*radius;
target[axis_2] = center_y+cos(theta)*radius;
plan_buffer_line(target[X_AXIS], target[Y_AXIS], target[Z_AXIS], feed_rate, invert_feed_rate);
void mc_go_home()