/* nybble/hex are little helpers to parse hexadecimal numbers to a byte value  */
static uint8_t nybble(const uint8_t n)
/* nybble/hex are little helpers to parse hexadecimal numbers to a byte value  */
static uint8_t nybble(const uint8_t n)
{
       if      (n >= '0' && n <= '9') return n - '0';
       else if (n >= 'A' && n <= 'F') return n - ('A' - 10);
       else if (n >= 'a' && n <= 'f') return n - ('a' - 10);
       return 0;
}