Updated variable spindle and new probing. Minor bug fixes.

- Minor bug fix for variable spindle PWM output. Values smaller than
the minimum RPM for the spindle would overflow the PWM value. Thanks
Rob!

- Created an optional minimum spindle PWM low-mark value as a
compile-time option. This is for special circumstances when the PWM has
to be at a certain level to be read by the spindle controller.

- Refactored the new probing commands (G38.3, G38.4, G38.5) code to
work better with the rest of Grbl’s systems.

- Refactored mc_probe() and mc_arc() to accept the mode of the command,
i.e. clockwise vs counter, toward vs away, etc. This is to make these
functions independent of gcode state variables.

- Removed the pull off motion in the probing cycle. This is not an
official operation and was added for user simplicity, but wrongly did
so. So bye bye.

- Created a configure probe invert mask function to handle the
different probe pin setting and probing cycle modes with a single mask.

 - Minor bug fix with reporting motion modes via $G. G38.2 wasn’t
showing up. It now does, along with the other new probing commands.

- Refactored some of the new pin configurations for the future of Grbl.

-

probe.h

@@ -22,25 +22,19 @@
 #define probe_h 
 
 // Values that define the probing state machine.  
-#define PROBE_OFF     0 // No probing. (Must be zero.)
+#define PROBE_OFF     0 // Probing disabled or not in use. (Must be zero.)
 #define PROBE_ACTIVE  1 // Actively watching the input pin.
 
-// Probe direction and error modes
-#define PROBE_AWAY 2 // G38.4, G38.5
-#define PROBE_NO_ERROR 4 // G38.3, G38.5
-
-#define PROBE_AWAY_BIT 1
-#define PROBE_NO_ERROR_BIT 2
-
 // Probe pin initialization routine.
 void probe_init();
 
-// Returns probe pin state.
-uint8_t probe_get_state(uint8_t mode);
+// Called by probe_init() and the mc_probe() routines. Sets up the probe pin invert mask to 
+// appropriately set the pin logic according to setting for normal-high/normal-low operation 
+// and the probing cycle modes for toward-workpiece/away-from-workpiece. 
+void probe_configure_invert_mask(uint8_t is_probe_away);
 
-uint8_t probe_errors_enabled(uint8_t mode);
-
-void probe_finalize(uint8_t probe_succeeded);
+// Returns probe pin state. Triggered = true. Called by gcode parser and probe state monitor.
+uint8_t probe_get_state();
 
 // Monitors probe pin state and records the system position when detected. Called by the
 // stepper ISR per ISR tick.