关于明华kfr-35 读卡器 修改密码有关问题

关于明华kfr-35 读卡器 修改密码问题
 skey = "ffffffffffff";
                    key1 = Encoding.ASCII.GetBytes(skey);
                    common.a_hex(key1, key2, 12);
                    st = common.rf_load_key(icdev, 0, iii, key2);
                    if (st != 0)
                    {
                        MessageBox.Show("密码装载失败！");
                        return;
                    }
                    st = common.rf_load_key(icdev, 4, iii, key2);
                    if (st != 0)
                    {
                        MessageBox.Show("密码装载失败！");
                        return;
                    }


                    common.rf_reset(icdev, 3);
                    st = common.rf_request(icdev, 1, out tagtype);
                    if (st != 0)
                    {
                        MessageBox.Show("request error!");

                        return;
                    }
                    st = common.rf_anticoll(icdev, 0, out snr);
                    if (st != 0)
                    {
                        MessageBox.Show("anticoll error!");
                        return;
                    }

                    snrstr = "";
                    snrstr = snr.ToString("X");


                    st = common.rf_select(icdev, snr, out size);
                    if (st != 0)
                    {
                        MessageBox.Show("select error!");
                        return;
                    }
                    st = common.rf_authentication(icdev, 0, iii);
                    if (st != 0)
                    {
                        MessageBox.Show("密码验证失败！");

                        return;
                    }
                    st = common.rf_authentication(icdev, 4, iii);
                    if (st != 0)
                    {
                        MessageBox.Show("密码验证失败！");
                        return;
                    }
                    skey = "fefefefefefefe";
                    key1 = Encoding.ASCII.GetBytes(skey);
                    common.a_hex(key1, key3, 30);
                    //st = common.rf_write_hex(icdev, 2, skey);
                    st = common.rf_changeb3(icdev, iii, key3, 0x04, 0x04, 0x04, 0x04, 0, key2);
                    if (st != 0)
                    {
                        MessageBox.Show("密码修改失败！");
                        return;
                    }

                    }


到了rf_changeb3 时怎么都改不了 下面是dll引用

  [DllImport("mwrf32.dll", EntryPoint = "rf_changeb3", SetLastError = true,
             CharSet = CharSet.Auto, ExactSpelling = false,
            CallingConvention = CallingConvention.StdCall)]
        public static extern Int16 rf_changeb3(int icdev, int secnr, [MarshalAs(UnmanagedType.LPArray)]byte[] keya, int b0, int b1, int b2, int b3, int bk, [MarshalAs(UnmanagedType.LPArray)]byte[] keyb);

[解决办法]
请问你装载密码是如何实现的呢？？我总是装载失败啊！！common.a_hex(key1, key2, 12);
是什么？？
[解决办法]
装载密码是rf_load_key,装载后才能authcation校对，　comomn.a_hex Ascii 转 16进制,

修改密码有人解决了吗？　调用　rf_changeb3　返回值总是为１
[解决办法]
因为你的控制指令没写对，应该是0xff, 0x7, 0x80, 0x69
[解决办法]