diff --git a/.gitignore b/.gitignore
index 8593707..844cd7a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
+*.hex
 *.o
 *.elf
 *.DS_Store
diff --git a/README.md b/README.md
index 44ddcda..e4ec6f9 100755
--- a/README.md
+++ b/README.md
@@ -14,7 +14,8 @@ _**Master Branch:**_
 * [Grbl v0.8c Atmega328p 16mhz 9600baud](http://bit.ly/SSdCJE)
 
 _**Edge/Development Branch:**_
-* [Grbl v0.9a Build 2012-12-10](http://bit.ly/UDBwpZ)
+* [Grbl v0.9a Build 2012-12-16](http://bit.ly/UUTOD4) : Axes acceleration and maximum velocity independence installed. Lowered 20kHz step rate max. Bugs still exist. For testing only. Settings WILL be over-written.
+* [Grbl v0.9a Build 2012-12-10](http://bit.ly/UDBwpZ) : New experimental stepper algorithm. Smoother. 30kHz max. Bugs exist (Homing). For testing only. Settings WILL be over-written.
 
 _**Archives:**_
 * [Grbl v0.8a Atmega328p 16mhz 9600baud](http://bit.ly/TVCTVv)
@@ -51,4 +52,4 @@ _**Archives:**_
 
 *Important note for Atmega 168 users:* Going forward, support for Atmega 168 will be dropped due to its limited memory and speed. However, legacy Grbl v0.51 "in the branch called 'v0_51' is still available for use.
 
-_The project was initially inspired by the Arduino GCode Interpreter by Mike Ellery_
+_The project was initially inspired by the Arduino GCode Interpreter by Mike Ellery_
\ No newline at end of file
diff --git a/defaults.h b/defaults.h
index 279e4b9..30e575d 100644
--- a/defaults.h
+++ b/defaults.h
@@ -55,14 +55,14 @@
 #endif
 
 #ifdef DEFAULTS_SHERLINE_5400
-  // Description: Sherline 5400 mill with three NEMA 23 185 oz-in stepper motors, driven by
-  // three Pololu A4988 stepper drivers with a 30V, 6A power supply at 1.5A per winding.
-  #define MICROSTEPS 4
+  // Description: Sherline 5400 mill with three NEMA 23 Keling  KL23H256-21-8B 185 oz-in stepper motors,
+  // driven by three Pololu A4988 stepper drivers with a 30V, 6A power supply at 1.5A per winding.
+  #define MICROSTEPS 2
   #define STEPS_PER_REV 200.0
-  #define MM_PER_REV (0.050*MM_PER_INCH)) // 0.050 inch/rev leadscrew
-  #define DEFAULT_X_STEPS_PER_MM (STEP_PER_REV*MICROSTEPS/MM_PER_REV)
-  #define DEFAULT_Y_STEPS_PER_MM (STEP_PER_REV*MICROSTEPS/MM_PER_REV)
-  #define DEFAULT_Z_STEPS_PER_MM (STEP_PER_REV*MICROSTEPS/MM_PER_REV)
+  #define MM_PER_REV (0.050*MM_PER_INCH) // 0.050 inch/rev leadscrew
+  #define DEFAULT_X_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
+  #define DEFAULT_Y_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
+  #define DEFAULT_Z_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
   #define DEFAULT_STEP_PULSE_MICROSECONDS 10
   #define DEFAULT_MM_PER_ARC_SEGMENT 0.1
   #define DEFAULT_RAPID_FEEDRATE 635.0 // mm/min (25ipm)
@@ -119,4 +119,36 @@
   #define DEFAULT_N_ARC_CORRECTION 25
 #endif
 
+#ifdef DEFAULTS_ZEN_TOOLWORKS_7x7
+  // Description: Zen Toolworks 7x7 mill with three Shinano SST43D2121 65oz-in NEMA 17 stepper motors.
+  // Leadscrew is different from some ZTW kits, where most are 1.25mm/rev rather than 8.0mm/rev here.
+  // Driven by 30V, 6A power supply and TI DRV8811 stepper motor drivers.
+  #define MICROSTEPS 8
+  #define STEPS_PER_REV 200.0
+  #define MM_PER_REV 8.0 // 8 mm/rev leadscrew
+  #define DEFAULT_X_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
+  #define DEFAULT_Y_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
+  #define DEFAULT_Z_STEPS_PER_MM (STEPS_PER_REV*MICROSTEPS/MM_PER_REV)
+  #define DEFAULT_STEP_PULSE_MICROSECONDS 10
+  #define DEFAULT_MM_PER_ARC_SEGMENT 0.1
+  #define DEFAULT_RAPID_FEEDRATE 2500.0 // mm/min
+  #define DEFAULT_FEEDRATE 1000.0 // mm/min
+  #define DEFAULT_ACCELERATION 150.0*60*60 // 150 mm/min^2
+  #define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
+  #define DEFAULT_STEPPING_INVERT_MASK (1<<Y_DIRECTION_BIT)
+  #define DEFAULT_REPORT_INCHES 0 // false
+  #define DEFAULT_AUTO_START 1 // true
+  #define DEFAULT_INVERT_ST_ENABLE 0 // false
+  #define DEFAULT_HARD_LIMIT_ENABLE 0  // false
+  #define DEFAULT_HOMING_ENABLE 0  // false
+  #define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
+  #define DEFAULT_HOMING_RAPID_FEEDRATE 500.0 // mm/min
+  #define DEFAULT_HOMING_FEEDRATE 50.0 // mm/min
+  #define DEFAULT_HOMING_DEBOUNCE_DELAY 100 // msec (0-65k)
+  #define DEFAULT_HOMING_PULLOFF 1.0 // mm
+  #define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-255)
+  #define DEFAULT_DECIMAL_PLACES 3
+  #define DEFAULT_N_ARC_CORRECTION 25
 #endif
+
+#endif
\ No newline at end of file
diff --git a/stepper.c b/stepper.c
index 28e6f50..7c0770b 100755
--- a/stepper.c
+++ b/stepper.c
@@ -263,9 +263,14 @@ ISR(TIMER1_COMPA_vect)
         } else if (st.step_events_completed >= current_block->decelerate_after) {
           // Reset trapezoid tick cycle counter to make sure that the deceleration is performed the
           // same every time. Reset to CYCLES_PER_ACCELERATION_TICK/2 to follow the midpoint rule for
-          // an accurate approximation of the deceleration curve.
+          // an accurate approximation of the deceleration curve. For triangle profiles, down count
+          // from current cycle counter to ensure exact deceleration curve.
           if (st.step_events_completed == current_block-> decelerate_after) {
-            st.trapezoid_tick_cycle_counter = CYCLES_PER_ACCELERATION_TICK/2;
+            if (st.trapezoid_adjusted_rate == current_block->nominal_rate) {
+              st.trapezoid_tick_cycle_counter = CYCLES_PER_ACCELERATION_TICK/2; // Trapezoid profile
+            } else {  
+              st.trapezoid_tick_cycle_counter = CYCLES_PER_ACCELERATION_TICK-st.trapezoid_tick_cycle_counter; // Triangle profile
+            }
           } else {
             // Iterate cycle counter and check if speeds need to be reduced.
             if ( iterate_trapezoid_cycle_counter() ) {