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/nuts_bolts.c

@@ -0,0 +1,148 @@
+/*
+  nuts_bolts.c - Shared functions
+  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"
+
+
+#define MAX_INT_DIGITS 8 // Maximum number of digits in int32 (and float)
+
+
+// Extracts a floating point value from a string. The following code is based loosely on
+// the avr-libc strtod() function by Michael Stumpf and Dmitry Xmelkov and many freely
+// available conversion method examples, but has been highly optimized for Grbl. For known
+// CNC applications, the typical decimal value is expected to be in the range of E0 to E-4.
+// Scientific notation is officially not supported by g-code, and the 'E' character may
+// be a g-code word on some CNC systems. So, 'E' notation will not be recognized. 
+// NOTE: Thanks to Radu-Eosif Mihailescu for identifying the issues with using strtod().
+uint8_t read_float(char *line, uint8_t *char_counter, float *float_ptr)                  
+{
+  char *ptr = line + *char_counter;
+  unsigned char c;
+    
+  // Grab first character and increment pointer. No spaces assumed in line.
+  c = *ptr++;
+  
+  // Capture initial positive/minus character
+  bool isnegative = false;
+  if (c == '-') {
+    isnegative = true;
+    c = *ptr++;
+  } else if (c == '+') {
+    c = *ptr++;
+  }
+  
+  // Extract number into fast integer. Track decimal in terms of exponent value.
+  uint32_t intval = 0;
+  int8_t exp = 0;
+  uint8_t ndigit = 0;
+  bool isdecimal = false;
+  while(1) {
+    c -= '0';
+    if (c <= 9) {
+      ndigit++;
+      if (ndigit <= MAX_INT_DIGITS) {
+        if (isdecimal) { exp--; }
+        intval = (((intval << 2) + intval) << 1) + c; // intval*10 + c
+      } else {
+        if (!(isdecimal)) { exp++; }  // Drop overflow digits
+      }
+    } else if (c == (('.'-'0') & 0xff)  &&  !(isdecimal)) {
+      isdecimal = true;
+    } else {
+      break;
+    }
+    c = *ptr++;
+  }
+  
+  // Return if no digits have been read.
+  if (!ndigit) { return(false); };
+  
+  // Convert integer into floating point.
+  float fval;
+  fval = (float)intval;
+  
+  // Apply decimal. Should perform no more than two floating point multiplications for the
+  // expected range of E0 to E-4.
+  if (fval != 0) {
+    while (exp <= -2) {
+      fval *= 0.01; 
+      exp += 2;
+    }
+    if (exp < 0) { 
+      fval *= 0.1; 
+    } else if (exp > 0) {
+      do {
+        fval *= 10.0;
+      } while (--exp > 0);
+    } 
+  }
+
+  // Assign floating point value with correct sign.    
+  if (isnegative) {
+    *float_ptr = -fval;
+  } else {
+    *float_ptr = fval;
+  }
+
+  *char_counter = ptr - line - 1; // Set char_counter to next statement
+  
+  return(true);
+}
+
+
+// Delays variable defined milliseconds. Compiler compatibility fix for _delay_ms(),
+// which only accepts constants in future compiler releases.
+void delay_ms(uint16_t ms) 
+{
+  while ( ms-- ) { _delay_ms(1); }
+}
+
+
+// Delays variable defined microseconds. Compiler compatibility fix for _delay_us(),
+// which only accepts constants in future compiler releases. Written to perform more 
+// efficiently with larger delays, as the counter adds parasitic time in each iteration.
+void delay_us(uint32_t us) 
+{
+  while (us) {
+    if (us < 10) { 
+      _delay_us(1);
+      us--;
+    } else if (us < 100) {
+      _delay_us(10);
+      us -= 10;
+    } else if (us < 1000) {
+      _delay_us(100);
+      us -= 100;
+    } else {
+      _delay_ms(1);
+      us -= 1000;
+    }
+  }
+}
+
+
+// Simple hypotenuse computation function.
+float hypot_f(float x, float y) { return(sqrt(x*x + y*y)); }