Import grbl v1.1h
diff --git a/grbl/stepper.h b/grbl/stepper.h
new file mode 100644
index 0000000..41871a6
--- /dev/null
+++ b/grbl/stepper.h
@@ -0,0 +1,59 @@
+/*
+ stepper.h - stepper motor driver: executes motion plans of planner.c using the stepper motors
+ Part of Grbl
+
+ Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
+ 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
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ 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 <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef stepper_h
+#define stepper_h
+
+#ifndef SEGMENT_BUFFER_SIZE
+ #define SEGMENT_BUFFER_SIZE 6
+#endif
+
+// Initialize and setup the stepper motor subsystem
+void stepper_init();
+
+// Enable steppers, but cycle does not start unless called by motion control or realtime command.
+void st_wake_up();
+
+// Immediately disables steppers
+void st_go_idle();
+
+// Generate the step and direction port invert masks.
+void st_generate_step_dir_invert_masks();
+
+// Reset the stepper subsystem variables
+void st_reset();
+
+// Changes the run state of the step segment buffer to execute the special parking motion.
+void st_parking_setup_buffer();
+
+// Restores the step segment buffer to the normal run state after a parking motion.
+void st_parking_restore_buffer();
+
+// Reloads step segment buffer. Called continuously by realtime execution system.
+void st_prep_buffer();
+
+// Called by planner_recalculate() when the executing block is updated by the new plan.
+void st_update_plan_block_parameters();
+
+// Called by realtime status reporting if realtime rate reporting is enabled in config.h.
+float st_get_realtime_rate();
+
+#endif