+/** make the robot orbiting around (x,y) on a circle whose radius is
+ * radius_mm, and exit when relative destination angle is reached. The
+ * flags set if we go forward or backwards, and CW/CCW. */
+void trajectory_circle_rel(struct trajectory *traj, double x, double y,
+ double radius_mm, double rel_a_deg, uint8_t flags);
+
+/* do a line */
+void trajectory_line_abs(struct trajectory *traj, double x1, double y1,
+ double x2, double y2, double advance);
+