// ==========================================================================
// CRC Generation Unit - Linear Feedback Shift Register implementation
// (c) Kay Gorontzi, GHSi.de, distributed under the terms of LGPL
// ==========================================================================
char *MakeCRC(char *BitString, unsigned char poly)
   {
   static char Res[9];                                 // CRC Result
   char CRC[8];
   int  i;
   char bitcnt;
   char DoInvert;
   
   for (i=0; i<8; ++i)  CRC[i] = 0;                    // Init before calculation
   
   for (i=0; i<strlen(BitString); ++i)
      {
//                 V  verander deze naar '0' voor inverted
      DoInvert = ('1'==BitString[i]) ^ CRC[7];         // XOR required?

      for (bitcnt=7; bitcnt > 0; bitcnt--) {
         if (poly & (1 << bitcnt)) {
           CRC[bitcnt] = CRC[bitcnt-1] ^ DoInvert;
         } else {
           CRC[bitcnt] = CRC[bitcnt-1];
         }
      }
      if (poly & 1) {
        CRC[0] = DoInvert;
      } else {
        CRC[0] = 0;
      }
      }
      
   for (i=0; i<8; ++i)  Res[7-i] = CRC[i] ? '1' : '0'; // Convert binary to ASCII
   Res[8] = 0;                                         // Set string terminator

   return(Res);
   }

// A simple test driver:

#include <stdio.h>

int main()
   {
   char *Data, *Result;                                       // Declare two strings
int cnt;



//   Data = "0001000011000001001000010010001000000001"; // straight
//   Data = "0001000011000001001000010010001000000000"; 

//   Data = "1000000001000100100001001000001100001000"; // compleet andersom
//   Data = "0000000001000100100001001000001100001000";

//   Data = "0000100010000011100001000100010010000000"; // msb first
   Data = "0000100010000011100001000100010000000000";
   
   for (cnt=0; cnt<256; cnt++) {
     Result = MakeCRC(Data, cnt);                                    // Calculate CRC
   
     printf("CRC of [s] with poly [%i] is [%s]\n", cnt, Result);
   }
   return(0);
   }