File re-organization. New Makefile.

- Re-organized source code files into a ‘grbl’ directory to lessen one
step in compiling Grbl through the Arduino IDE.

- Added an ‘examples’ directory with an upload .INO sketch to further
simplify compiling and uploading Grbl via the Arduino IDE.

- Updated the Makefile with regard to the source code no longer being
in the root directory. All files generated by compiling is placed in a
separate ‘build’ directory to keep things tidy. The makefile should
operate in the same way as it did before.

grbl/probe.c

@@ -0,0 +1,68 @@
+/*
+  probe.c - code pertaining to probing methods
+  Part of Grbl v0.9
+
+  Copyright (c) 2014-2015 Sungeun K. Jeon
+
+  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"
+
+
+// Inverts the probe pin state depending on user settings and probing cycle mode.
+uint8_t probe_invert_mask;
+
+
+// Probe pin initialization routine.
+void probe_init() 
+{
+  PROBE_DDR &= ~(PROBE_MASK); // Configure as input pins
+  #ifdef DISABLE_PROBE_PIN_PULL_UP
+    PROBE_PORT &= ~(PROBE_MASK); // Normal low operation. Requires external pull-down.
+  #else
+    PROBE_PORT |= PROBE_MASK;    // Enable internal pull-up resistors. Normal high operation.
+  #endif
+  // probe_configure_invert_mask(false); // Initialize invert mask. Not required. Updated when in-use.
+}
+
+
+// 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)
+{
+  probe_invert_mask = 0; // Initialize as zero.
+  if (bit_isfalse(settings.flags,BITFLAG_INVERT_PROBE_PIN)) { probe_invert_mask ^= PROBE_MASK; }
+  if (is_probe_away) { probe_invert_mask ^= PROBE_MASK; }
+}
+
+
+// Returns the probe pin state. Triggered = true. Called by gcode parser and probe state monitor.
+uint8_t probe_get_state() { return((PROBE_PIN & PROBE_MASK) ^ probe_invert_mask); }
+
+
+// Monitors probe pin state and records the system position when detected. Called by the
+// stepper ISR per ISR tick.
+// NOTE: This function must be extremely efficient as to not bog down the stepper ISR.
+void probe_state_monitor()
+{
+  if (sys.probe_state == PROBE_ACTIVE) {
+    if (probe_get_state()) {
+      sys.probe_state = PROBE_OFF;
+      memcpy(sys.probe_position, sys.position, sizeof(float)*N_AXIS);
+      bit_true(sys.rt_exec_state, EXEC_FEED_HOLD);
+    }
+  }
+}