Graycode Umwandlung

nospam@example.com (Lothar Miller) — Sun, 17 Jan 2010 19:07:00 +0100

Hier finden sich C-Routinen zur Umwandlung von Graycode nach Binärcode und umgekehrt. Das Ganze basiert auf dem VHDL-Code hier: Graycode-Umwandlung in VHDL

/*
The purpose of this function is to convert an unsigned
binary number to reflected binary Gray code.
Binary 1-x-0-x-1-x-0-x-1
       |  `   `   `   ` 
       |   |   |   |   |       x = xor
       v   v   v   v   v       Abarbeitung MSB ... LSB 
Gray   1   1   0   0   1
*/
unsigned short BinaryToGray(unsigned short num)
{
   return (num>>1) ^ num;
}

/*
A tricky trick: for up to 2^n bits, you can convert Gray to binary by
performing (2^n) - 1 binary-to Gray conversions. All you need is the
function above and a 'for' loop.
*/
unsigned short GrayToBinary(unsigned short num)
{
  int i;
  unsigned short temp = num;
  for (i=0; i<15; i++) temp = BinaryToGray(temp);
  return temp;
}

/*
Gray   1   0   1   0   1
       |  /   /   /   / 
       | x   x   x   x     x = xor
       v/ `v/ `v/ `v/ `v   Abarbeitung MSB ... LSB 
Binary 1   1   0   0   1   
*/
unsigned short GrayToBinaryX(unsigned short num)
{
  int i;
  unsigned short temp = num;
  temp &= 0x8000;
  for (i=14; i>=0; i--) {
     if ( (!!(temp&(1<<(i+1)))) != (!!(num&(1<<i))) )
        temp |= (1<<i);
  }
  return temp;
}

/*
The purpose of this function is to convert a reflected binary
Gray code number to a binary number.
*/
unsigned short GrayToBinaryPow2(unsigned short num)
{
  unsigned short temp = num;
  temp ^= (temp>>8);
  temp ^= (temp>>4);
  temp ^= (temp>>2);
  temp ^= (temp>>1);
  return temp;
}

Die Grundlagen dieser Umwandlungsroutinen sind auf www.wisc-online.com schön erklärt.

Lothar Miller - Graycode

Graycode Umwandlung