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/main.c

@@ -0,0 +1,90 @@
+/*
+  main.c - An embedded CNC Controller with rs274/ngc (g-code) support
+  Part of Grbl v0.9
+  
+  Copyright (c) 2012-2015 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/>.
+*/
+/* 
+  This file is based on work from Grbl v0.8, distributed under the 
+  terms of the MIT-license. See COPYING for more details.  
+    Copyright (c) 2009-2011 Simen Svale Skogsrud
+    Copyright (c) 2011-2012 Sungeun K. Jeon
+*/  
+
+#include "grbl.h"
+
+
+// Declare system global variable structure
+system_t sys; 
+
+
+int main(void)
+{
+  // Initialize system upon power-up.
+  serial_init();   // Setup serial baud rate and interrupts
+  settings_init(); // Load Grbl settings from EEPROM
+  stepper_init();  // Configure stepper pins and interrupt timers
+  system_init();   // Configure pinout pins and pin-change interrupt
+  
+  memset(&sys, 0, sizeof(sys));  // Clear all system variables
+  sys.abort = true;   // Set abort to complete initialization
+  sei(); // Enable interrupts
+
+  // Check for power-up and set system alarm if homing is enabled to force homing cycle
+  // by setting Grbl's alarm state. Alarm locks out all g-code commands, including the
+  // startup scripts, but allows access to settings and internal commands. Only a homing
+  // cycle '$H' or kill alarm locks '$X' will disable the alarm.
+  // NOTE: The startup script will run after successful completion of the homing cycle, but
+  // not after disabling the alarm locks. Prevents motion startup blocks from crashing into
+  // things uncontrollably. Very bad.
+  #ifdef HOMING_INIT_LOCK
+    if (bit_istrue(settings.flags,BITFLAG_HOMING_ENABLE)) { sys.state = STATE_ALARM; }
+  #endif
+  
+  // Grbl initialization loop upon power-up or a system abort. For the latter, all processes
+  // will return to this loop to be cleanly re-initialized.
+  for(;;) {
+
+    // TODO: Separate configure task that require interrupts to be disabled, especially upon
+    // a system abort and ensuring any active interrupts are cleanly reset.
+  
+    // Reset Grbl primary systems.
+    serial_reset_read_buffer(); // Clear serial read buffer
+    gc_init(); // Set g-code parser to default state
+    spindle_init();
+    coolant_init();
+    limits_init(); 
+    probe_init();
+    plan_reset(); // Clear block buffer and planner variables
+    st_reset(); // Clear stepper subsystem variables.
+
+    // Sync cleared gcode and planner positions to current system position.
+    plan_sync_position();
+    gc_sync_position();
+
+    // Reset system variables.
+    sys.abort = false;
+    sys.rt_exec_state = 0;
+    sys.rt_exec_alarm = 0;
+    if (bit_istrue(settings.flags,BITFLAG_AUTO_START)) { sys.auto_start = true; }
+    else { sys.auto_start = false; }
+          
+    // Start Grbl main loop. Processes program inputs and executes them.
+    protocol_main_loop();
+    
+  }
+  return 0;   /* Never reached */
+}