grbl-LPC-CoreXY/nuts_bolts.c

/*
  nuts_bolts.c - Shared functions
  Part of Grbl

  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Copyright (c) 2011-2012 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 "nuts_bolts.h"
#include <util/delay.h>

#define MAX_INT_DIGITS 8 // Maximum number of digits in int32 (and float)
extern float __floatunsisf (unsigned long);

// 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().
int 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 = __floatunsisf(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;
    }
  }
}