The solution for example 10.2, on page 136-137 is incorrect. When variable a and b are 'A'-'F', the conversion should be:

a = a - 'A' + 10;

b = b - 'A' + 10;

And remember, it only converts uppercase hex values.

The complete function is then:

void TxtToHexFast (BYTE *pHex, char Txt[], int length)

{

      int i, a, b;

      for (i=0; i<length; i++)

      {

            a = (int)Txt[i*2];

            b = (int)Txt[i*2+1];

            if (a >= 'A')

                  a = a-'A'+10;

            else

                  a = a-'0';

            if (b >= 'A')

                  b = b-'A'+10;

            else

                  b = b-'0';

            pHex[i] = (BYTE)((a<<4) + b);

      }

}