diff --git a/cpu_map.h b/cpu_map.h
index 060135a..797f6bf 100644
--- a/cpu_map.h
+++ b/cpu_map.h
@@ -223,10 +223,17 @@
   #define PINOUT_PCMSK     PCMSK2 // Pin change interrupt register
   #define PINOUT_MASK ((1<<PIN_RESET)|(1<<PIN_FEED_HOLD)|(1<<PIN_CYCLE_START))
 
+  // Define probe switch input pin.
+  #define PROBE_DDR       DDRK
+  #define PROBE_PIN       PINK
+  #define PROBE_PORT      PORTK
+  #define PROBE_BIT       3  // MEGA2560 Analog Pin 11
+  #define PROBE_MASK      (1<<PROBE_BIT)
+
   // Start of PWM & Stepper Enabled Spindle
   #ifdef VARIABLE_SPINDLE
     // Advanced Configuration Below You should not need to touch these variables
-    // Set Timer up to use TIMER4 OCR4B which is attached to Digital Pin 7
+    // Set Timer up to use TIMER2B which is attached to Digital Pin 9
     #define TCCRA_REGISTER		TCCR2A
     #define TCCRB_REGISTER		TCCR2B
     #define OCR_REGISTER		OCR2B
diff --git a/defaults.h b/defaults.h
index a1de3fe..415a44c 100644
--- a/defaults.h
+++ b/defaults.h
@@ -169,7 +169,8 @@
   #define DEFAULT_Z_MAX_TRAVEL 200.0 // mm
   #define DEFAULT_STEP_PULSE_MICROSECONDS 10
   #define DEFAULT_FEEDRATE 250.0
-  #define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
+  #define DEFAULT_STEPPING_INVERT_MASK 0
+  #define DEFAULT_DIRECTION_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
   #define DEFAULT_STEPPER_IDLE_LOCK_TIME 255 // msec (0-254, 255 keeps steppers enabled)
   #define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
   #define DEFAULT_ARC_TOLERANCE 0.002 // mm