shiftIn.c

/*
 * @file shiftIn.c
 *
 * @author Andy Lindsay
 *
 * @version 0.85
 *
 * @copyright Copyright (C) Parallax, Inc. 2012.  See end of file for
 * terms of use (MIT License).
 *
 * @brief shiftIn function source, see simpletools.h for documentation.
 *
 * @detail Please submit bug reports, suggestions, and improvements to
 * this code to editor@parallax.com.
 */
 
#include "simpletools.h"                         // simpletools function prototypes
 
// shiftIn function definition
int shift_in(int pinDat, int pinClk, int mode, int bits)
{
  int vi, vf, inc;
  int value = 0; 
  int preflag = 0;
  if((mode == MSBPRE)||(mode == LSBPRE)) preflag = 1;
  switch(mode)
  {
    case MSBPRE:
      vi = bits - 1;
      vf = -1;
      inc = -1;
      //value |= (input(pinDat) << bits);
      break;
    case LSBPRE:
      vi = 0;
      vf = bits;
      inc = 1;
      value |= input(pinDat);
      break;
    case MSBPOST:
      vi = bits -1;
      vf = -1;
      inc = -1;
      break;
    default: // case LSBPOST:
      vi = 0;
      vf = bits;
      inc = 1;
      break;
  }   
  low(pinClk);
  int i;
  for(i = vi; i != vf; i += inc)
  {
    if(preflag) value |= (input(pinDat) << i); 
    toggle(pinClk);
    toggle(pinClk);
    //if(!i)
    //{
    //  if(preflag) break;
    //}
    if(!preflag) value |= (input(pinDat) << i); 
  }
  return value;
}