Added complete stop delay at the end of all motion. Moved grbl preprocessor script into a new repository.

Added a very short (25 ms) user-definable delay before the steppers are
disabled at the motors are disabled and grbl goes idle. This ensures
any residual inertia at the end of the last motion does not cause the
axes to drift and grbl to lose its position when manually entering
g-code or when performing a tool change and starting the next
operation.

config.h

@@ -56,8 +56,16 @@
 #define SPINDLE_DIRECTION_PORT PORTB
 #define SPINDLE_DIRECTION_BIT 5
 
-// The temporal resolution of the acceleration management subsystem. Higher number
-// give smoother acceleration but may impact performance
+// This parameter sets the delay time before disabling the steppers after the final block of movement.
+// A short delay ensures the steppers come to a complete stop and the residual inertial force in the 
+// CNC axes don't cause the axes to drift off position. This is particularly important when manually 
+// entering g-code into grbl, i.e. locating part zero or simple manual machining. If the axes drift,
+// grbl has no way to know this has happened, since stepper motors are open-loop control. Depending
+// on the machine, this parameter may need to be larger or smaller than the default time.
+#define STEPPER_IDLE_LOCK_TIME 25 // (milliseconds)
+
+// The temporal resolution of the acceleration management subsystem. Higher number give smoother
+// acceleration but may impact performance.
 // NOTE: Increasing this parameter will help any resolution related issues, especially with machines 
 // requiring very high accelerations and/or very fast feedrates. In general, this will reduce the 
 // error between how the planner plans the motions and how the stepper program actually performs them.