Merge pull request #261 from lagnat/negative-radius

Fix for negative arc radius support

firmware/tinyg/plan_arc.c

@@ -77,7 +77,7 @@ stat_t cm_arc_feed(float target[], float flags[],       // arc endpoints
 
     // set radius mode flag and do simple test(s)
 	bool radius_f = fp_NOT_ZERO(cm.gf.arc_radius);			    // set true if radius arc
-    if ((radius_f) && (cm.gn.arc_radius < MIN_ARC_RADIUS)) {    // radius value must be + and > minimum radius
+    if ((radius_f) && (fabs(cm.gn.arc_radius) < MIN_ARC_RADIUS)) {    // radius value must > minimum radius
         return (STAT_ARC_RADIUS_OUT_OF_TOLERANCE);
     }
 
@@ -243,32 +243,32 @@ void cm_abort_arc()
 static stat_t _compute_arc()
 {
 	// Compute radius. A non-zero radius value indicates a radius arc
-    if (fp_NOT_ZERO(arc.radius)) {                  // indicates a radius arc
-        _compute_arc_offsets_from_radius();
-    } else {                                        // compute start radius
-        arc.radius = hypotf(-arc.offset[arc.plane_axis_0], -arc.offset[arc.plane_axis_1]);
-    }
-
-    // Test arc specification for correctness according to:
-    // http://linuxcnc.org/docs/html/gcode/gcode.html#sec:G2-G3-Arc
-    // "It is an error if: when the arc is projected on the selected plane, the distance from
-    //  the current point to the center differs from the distance from the end point to the
-    //  center by more than (.05 inch/.5 mm) OR ((.0005 inch/.005mm) AND .1% of radius)."
-
-    // Compute end radius from the center of circle (offsets) to target endpoint
-    float end_0 = arc.gm.target[arc.plane_axis_0] - arc.position[arc.plane_axis_0] - arc.offset[arc.plane_axis_0];
-    float end_1 = arc.gm.target[arc.plane_axis_1] - arc.position[arc.plane_axis_1] - arc.offset[arc.plane_axis_1];
-    float err = fabs(hypotf(end_0, end_1) - arc.radius);   // end radius - start radius
-    if ( (err > ARC_RADIUS_ERROR_MAX) || 
-        ((err < ARC_RADIUS_ERROR_MIN) && 
-         (err > arc.radius * ARC_RADIUS_TOLERANCE)) ) {
-//        return (STAT_ARC_HAS_IMPOSSIBLE_CENTER_POINT);
-        return (STAT_ARC_SPECIFICATION_ERROR);
-    }
+    if (fp_NOT_ZERO(arc.radius)) {                  // indicates a radius arc
+        _compute_arc_offsets_from_radius();
+    } else {                                        // compute start radius
+        arc.radius = hypotf(-arc.offset[arc.plane_axis_0], -arc.offset[arc.plane_axis_1]);
+    }
+
+    // Test arc specification for correctness according to:
+    // http://linuxcnc.org/docs/html/gcode/gcode.html#sec:G2-G3-Arc
+    // "It is an error if: when the arc is projected on the selected plane, the distance from
+    //  the current point to the center differs from the distance from the end point to the
+    //  center by more than (.05 inch/.5 mm) OR ((.0005 inch/.005mm) AND .1% of radius)."
+
+    // Compute end radius from the center of circle (offsets) to target endpoint
+    float end_0 = arc.gm.target[arc.plane_axis_0] - arc.position[arc.plane_axis_0] - arc.offset[arc.plane_axis_0];
+    float end_1 = arc.gm.target[arc.plane_axis_1] - arc.position[arc.plane_axis_1] - arc.offset[arc.plane_axis_1];
+    float err = fabs(hypotf(end_0, end_1) - arc.radius);   // end radius - start radius
+    if ( (err > ARC_RADIUS_ERROR_MAX) || 
+        ((err < ARC_RADIUS_ERROR_MIN) && 
+         (err > arc.radius * ARC_RADIUS_TOLERANCE)) ) {
+//        return (STAT_ARC_HAS_IMPOSSIBLE_CENTER_POINT);
+        return (STAT_ARC_SPECIFICATION_ERROR);
+    }
 
 	// Calculate the theta (angle) of the current point (position)
 	// arc.theta is angular starting point for the arc (also needed later for calculating center point)
-    arc.theta = atan2(-arc.offset[arc.plane_axis_0], -arc.offset[arc.plane_axis_1]);
+    arc.theta = atan2(-arc.offset[arc.plane_axis_0], -arc.offset[arc.plane_axis_1]);
 
     // g18_correction is used to invert G18 XZ plane arcs for proper CW orientation
     float g18_correction = (cm.gm.select_plane == CANON_PLANE_XZ) ? -1 : 1;
@@ -433,12 +433,16 @@ static stat_t _compute_arc_offsets_from_radius()
 	// such circles in a single line of g-code. By inverting the sign of
 	// h_x2_div_d the center of the circles is placed on the opposite side of
 	// the line of travel and thus we get the unadvisably long arcs as prescribed.
-	if (arc.radius < 0) { h_x2_div_d = -h_x2_div_d; }
+	if (arc.radius < 0) {
+        h_x2_div_d = -h_x2_div_d;
+        arc.radius *= -1;
+    }
 
 	// Complete the operation by calculating the actual center of the arc
 	arc.offset[arc.plane_axis_0] = (x-(y*h_x2_div_d))/2;
 	arc.offset[arc.plane_axis_1] = (y+(x*h_x2_div_d))/2;
 	arc.offset[arc.linear_axis] = 0;
+
 	return (STAT_OK);
 }
 
@@ -557,4 +561,4 @@ static stat_t _test_arc_soft_limits()
 	return(STAT_OK);
 }
 
-*/
+*/