code: function hexChar2byte(c) {
    var d = 0;
    if (c >= 'A' && c <= 'F') {
      d = c.charCodeAt(0) - 'A'.charCodeAt(0) + 10;
    }
    else if (c >= 'a' && c <= 'f') {
      d = c.charCodeAt(0) - 'a'.charCodeAt(0) + 10;
    }
    else if (c >= '0' && c <= '9') {
      d = c.charCodeAt(0) - '0'.charCodeAt(0);
    }
    return d;
  }
docs: /* Convert a hex char to value