Import grbl v1.1h
diff --git a/grbl/spindle_control.c b/grbl/spindle_control.c
new file mode 100644
index 0000000..550b752
--- /dev/null
+++ b/grbl/spindle_control.c
@@ -0,0 +1,290 @@
+/*
+  spindle_control.c - spindle control methods
+  Part of Grbl
+
+  Copyright (c) 2012-2017 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/>.
+*/
+
+#include "grbl.h"
+
+
+#ifdef VARIABLE_SPINDLE
+  static float pwm_gradient; // Precalulated value to speed up rpm to PWM conversions.
+#endif
+
+
+void spindle_init()
+{
+  #ifdef VARIABLE_SPINDLE
+    // Configure variable spindle PWM and enable pin, if requried. On the Uno, PWM and enable are
+    // combined unless configured otherwise.
+    SPINDLE_PWM_DDR |= (1<<SPINDLE_PWM_BIT); // Configure as PWM output pin.
+    SPINDLE_TCCRA_REGISTER = SPINDLE_TCCRA_INIT_MASK; // Configure PWM output compare timer
+    SPINDLE_TCCRB_REGISTER = SPINDLE_TCCRB_INIT_MASK;
+    #ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
+      SPINDLE_ENABLE_DDR |= (1<<SPINDLE_ENABLE_BIT); // Configure as output pin.
+    #else
+      #ifndef ENABLE_DUAL_AXIS
+        SPINDLE_DIRECTION_DDR |= (1<<SPINDLE_DIRECTION_BIT); // Configure as output pin.
+      #endif
+    #endif
+    pwm_gradient = SPINDLE_PWM_RANGE/(settings.rpm_max-settings.rpm_min);
+  #else
+    SPINDLE_ENABLE_DDR |= (1<<SPINDLE_ENABLE_BIT); // Configure as output pin.
+    #ifndef ENABLE_DUAL_AXIS
+      SPINDLE_DIRECTION_DDR |= (1<<SPINDLE_DIRECTION_BIT); // Configure as output pin.
+    #endif
+  #endif
+
+  spindle_stop();
+}
+
+
+uint8_t spindle_get_state()
+{
+  #ifdef VARIABLE_SPINDLE
+    #ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
+      // No spindle direction output pin. 
+      #ifdef INVERT_SPINDLE_ENABLE_PIN
+        if (bit_isfalse(SPINDLE_ENABLE_PORT,(1<<SPINDLE_ENABLE_BIT))) { return(SPINDLE_STATE_CW); }
+      #else
+        if (bit_istrue(SPINDLE_ENABLE_PORT,(1<<SPINDLE_ENABLE_BIT))) { return(SPINDLE_STATE_CW); }
+      #endif
+    #else
+      if (SPINDLE_TCCRA_REGISTER & (1<<SPINDLE_COMB_BIT)) { // Check if PWM is enabled.
+        #ifdef ENABLE_DUAL_AXIS
+          return(SPINDLE_STATE_CW);
+        #else
+          if (SPINDLE_DIRECTION_PORT & (1<<SPINDLE_DIRECTION_BIT)) { return(SPINDLE_STATE_CCW); }
+          else { return(SPINDLE_STATE_CW); }
+        #endif
+      }
+    #endif
+  #else
+    #ifdef INVERT_SPINDLE_ENABLE_PIN
+      if (bit_isfalse(SPINDLE_ENABLE_PORT,(1<<SPINDLE_ENABLE_BIT))) { 
+    #else
+      if (bit_istrue(SPINDLE_ENABLE_PORT,(1<<SPINDLE_ENABLE_BIT))) {
+    #endif
+      #ifdef ENABLE_DUAL_AXIS    
+        return(SPINDLE_STATE_CW);
+      #else
+        if (SPINDLE_DIRECTION_PORT & (1<<SPINDLE_DIRECTION_BIT)) { return(SPINDLE_STATE_CCW); }
+        else { return(SPINDLE_STATE_CW); }
+      #endif
+    }
+  #endif
+  return(SPINDLE_STATE_DISABLE);
+}
+
+
+// Disables the spindle and sets PWM output to zero when PWM variable spindle speed is enabled.
+// Called by various main program and ISR routines. Keep routine small, fast, and efficient.
+// Called by spindle_init(), spindle_set_speed(), spindle_set_state(), and mc_reset().
+void spindle_stop()
+{
+  #ifdef VARIABLE_SPINDLE
+    SPINDLE_TCCRA_REGISTER &= ~(1<<SPINDLE_COMB_BIT); // Disable PWM. Output voltage is zero.
+    #ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
+      #ifdef INVERT_SPINDLE_ENABLE_PIN
+        SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);  // Set pin to high
+      #else
+        SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT); // Set pin to low
+      #endif
+    #endif
+  #else
+    #ifdef INVERT_SPINDLE_ENABLE_PIN
+      SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);  // Set pin to high
+    #else
+      SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT); // Set pin to low
+    #endif
+  #endif
+}
+
+
+#ifdef VARIABLE_SPINDLE
+  // Sets spindle speed PWM output and enable pin, if configured. Called by spindle_set_state()
+  // and stepper ISR. Keep routine small and efficient.
+  void spindle_set_speed(uint8_t pwm_value)
+  {
+    SPINDLE_OCR_REGISTER = pwm_value; // Set PWM output level.
+    #ifdef SPINDLE_ENABLE_OFF_WITH_ZERO_SPEED
+      if (pwm_value == SPINDLE_PWM_OFF_VALUE) {
+        spindle_stop();
+      } else {
+        SPINDLE_TCCRA_REGISTER |= (1<<SPINDLE_COMB_BIT); // Ensure PWM output is enabled.
+        #ifdef INVERT_SPINDLE_ENABLE_PIN
+          SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT);
+        #else
+          SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);
+        #endif
+      }
+    #else
+      if (pwm_value == SPINDLE_PWM_OFF_VALUE) {
+        SPINDLE_TCCRA_REGISTER &= ~(1<<SPINDLE_COMB_BIT); // Disable PWM. Output voltage is zero.
+      } else {
+        SPINDLE_TCCRA_REGISTER |= (1<<SPINDLE_COMB_BIT); // Ensure PWM output is enabled.
+      }
+    #endif
+  }
+
+
+  #ifdef ENABLE_PIECEWISE_LINEAR_SPINDLE
+  
+    // Called by spindle_set_state() and step segment generator. Keep routine small and efficient.
+    uint8_t spindle_compute_pwm_value(float rpm) // 328p PWM register is 8-bit.
+    {
+      uint8_t pwm_value;
+      rpm *= (0.010*sys.spindle_speed_ovr); // Scale by spindle speed override value.
+      // Calculate PWM register value based on rpm max/min settings and programmed rpm.
+      if ((settings.rpm_min >= settings.rpm_max) || (rpm >= RPM_MAX)) {
+        rpm = RPM_MAX;
+        pwm_value = SPINDLE_PWM_MAX_VALUE;
+      } else if (rpm <= RPM_MIN) {
+        if (rpm == 0.0) { // S0 disables spindle
+          pwm_value = SPINDLE_PWM_OFF_VALUE;
+        } else {
+          rpm = RPM_MIN;
+          pwm_value = SPINDLE_PWM_MIN_VALUE;
+        }
+      } else {
+        // Compute intermediate PWM value with linear spindle speed model via piecewise linear fit model.
+        #if (N_PIECES > 3)
+          if (rpm > RPM_POINT34) {
+            pwm_value = floor(RPM_LINE_A4*rpm - RPM_LINE_B4);
+          } else 
+        #endif
+        #if (N_PIECES > 2)
+          if (rpm > RPM_POINT23) {
+            pwm_value = floor(RPM_LINE_A3*rpm - RPM_LINE_B3);
+          } else 
+        #endif
+        #if (N_PIECES > 1)
+          if (rpm > RPM_POINT12) {
+            pwm_value = floor(RPM_LINE_A2*rpm - RPM_LINE_B2);
+          } else 
+        #endif
+        {
+          pwm_value = floor(RPM_LINE_A1*rpm - RPM_LINE_B1);
+        }
+      }
+      sys.spindle_speed = rpm;
+      return(pwm_value);
+    }
+    
+  #else 
+  
+    // Called by spindle_set_state() and step segment generator. Keep routine small and efficient.
+    uint8_t spindle_compute_pwm_value(float rpm) // 328p PWM register is 8-bit.
+    {
+      uint8_t pwm_value;
+      rpm *= (0.010*sys.spindle_speed_ovr); // Scale by spindle speed override value.
+      // Calculate PWM register value based on rpm max/min settings and programmed rpm.
+      if ((settings.rpm_min >= settings.rpm_max) || (rpm >= settings.rpm_max)) {
+        // No PWM range possible. Set simple on/off spindle control pin state.
+        sys.spindle_speed = settings.rpm_max;
+        pwm_value = SPINDLE_PWM_MAX_VALUE;
+      } else if (rpm <= settings.rpm_min) {
+        if (rpm == 0.0) { // S0 disables spindle
+          sys.spindle_speed = 0.0;
+          pwm_value = SPINDLE_PWM_OFF_VALUE;
+        } else { // Set minimum PWM output
+          sys.spindle_speed = settings.rpm_min;
+          pwm_value = SPINDLE_PWM_MIN_VALUE;
+        }
+      } else { 
+        // Compute intermediate PWM value with linear spindle speed model.
+        // NOTE: A nonlinear model could be installed here, if required, but keep it VERY light-weight.
+        sys.spindle_speed = rpm;
+        pwm_value = floor((rpm-settings.rpm_min)*pwm_gradient) + SPINDLE_PWM_MIN_VALUE;
+      }
+      return(pwm_value);
+    }
+    
+  #endif
+#endif
+
+
+// Immediately sets spindle running state with direction and spindle rpm via PWM, if enabled.
+// Called by g-code parser spindle_sync(), parking retract and restore, g-code program end,
+// sleep, and spindle stop override.
+#ifdef VARIABLE_SPINDLE
+  void spindle_set_state(uint8_t state, float rpm)
+#else
+  void _spindle_set_state(uint8_t state)
+#endif
+{
+  if (sys.abort) { return; } // Block during abort.
+
+  if (state == SPINDLE_DISABLE) { // Halt or set spindle direction and rpm.
+  
+    #ifdef VARIABLE_SPINDLE
+      sys.spindle_speed = 0.0;
+    #endif
+    spindle_stop();
+  
+  } else {
+    
+    #if !defined(USE_SPINDLE_DIR_AS_ENABLE_PIN) && !defined(ENABLE_DUAL_AXIS)
+      if (state == SPINDLE_ENABLE_CW) {
+        SPINDLE_DIRECTION_PORT &= ~(1<<SPINDLE_DIRECTION_BIT);
+      } else {
+        SPINDLE_DIRECTION_PORT |= (1<<SPINDLE_DIRECTION_BIT);
+      }
+    #endif
+  
+    #ifdef VARIABLE_SPINDLE
+      // NOTE: Assumes all calls to this function is when Grbl is not moving or must remain off.
+      if (settings.flags & BITFLAG_LASER_MODE) { 
+        if (state == SPINDLE_ENABLE_CCW) { rpm = 0.0; } // TODO: May need to be rpm_min*(100/MAX_SPINDLE_SPEED_OVERRIDE);
+      }
+      spindle_set_speed(spindle_compute_pwm_value(rpm));
+    #endif
+    #if (defined(USE_SPINDLE_DIR_AS_ENABLE_PIN) && \
+        !defined(SPINDLE_ENABLE_OFF_WITH_ZERO_SPEED)) || !defined(VARIABLE_SPINDLE)
+      // NOTE: Without variable spindle, the enable bit should just turn on or off, regardless
+      // if the spindle speed value is zero, as its ignored anyhow.
+      #ifdef INVERT_SPINDLE_ENABLE_PIN
+        SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT);
+      #else
+        SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);
+      #endif    
+    #endif
+  
+  }
+  
+  sys.report_ovr_counter = 0; // Set to report change immediately
+}
+
+
+// G-code parser entry-point for setting spindle state. Forces a planner buffer sync and bails 
+// if an abort or check-mode is active.
+#ifdef VARIABLE_SPINDLE
+  void spindle_sync(uint8_t state, float rpm)
+  {
+    if (sys.state == STATE_CHECK_MODE) { return; }
+    protocol_buffer_synchronize(); // Empty planner buffer to ensure spindle is set when programmed.
+    spindle_set_state(state,rpm);
+  }
+#else
+  void _spindle_sync(uint8_t state)
+  {
+    if (sys.state == STATE_CHECK_MODE) { return; }
+    protocol_buffer_synchronize(); // Empty planner buffer to ensure spindle is set when programmed.
+    _spindle_set_state(state);
+  }
+#endif