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/serial.h

@@ -0,0 +1,69 @@
+/*
+  serial.c - Low level functions for sending and recieving bytes via the serial port
+  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
+*/ 
+
+#ifndef serial_h
+#define serial_h
+
+
+#ifndef RX_BUFFER_SIZE
+  #define RX_BUFFER_SIZE 128
+#endif
+#ifndef TX_BUFFER_SIZE
+  #define TX_BUFFER_SIZE 64
+#endif
+
+#define SERIAL_NO_DATA 0xff
+
+#ifdef ENABLE_XONXOFF
+  #define RX_BUFFER_FULL 96 // XOFF high watermark
+  #define RX_BUFFER_LOW 64 // XON low watermark
+  #define SEND_XOFF 1
+  #define SEND_XON 2
+  #define XOFF_SENT 3
+  #define XON_SENT 4
+  #define XOFF_CHAR 0x13
+  #define XON_CHAR 0x11
+#endif
+
+void serial_init();
+
+// Writes one byte to the TX serial buffer. Called by main program.
+void serial_write(uint8_t data);
+
+// Fetches the first byte in the serial read buffer. Called by main program.
+uint8_t serial_read();
+
+// Reset and empty data in read buffer. Used by e-stop and reset.
+void serial_reset_read_buffer();
+
+// Returns the number of bytes used in the RX serial buffer.
+uint8_t serial_get_rx_buffer_count();
+
+// Returns the number of bytes used in the TX serial buffer.
+// NOTE: Not used except for debugging and ensuring no TX bottlenecks.
+uint8_t serial_get_tx_buffer_count();
+
+#endif