MifareUltralight:扇区选择导致TagLostException

时间:2016-12-06 04:56:07

标签: java android nfc rfid mifare

我正在尝试使用SECTOR_SELECT对指定扇区进行读写,但在通过TagLostException发送命令的第二部分时获得MifareUltralight.transceive()。我如何选择和操纵扇区?

我正在使用Android Nexus 6(6.0.1)向NXP NTAG(NT3H1201)发送命令并从中获取数据。我可以使用GET_VERSION命令(60h)进行收发(通过NfcAMifareUltralight)。

我用来选择某个扇区的方法:

public void selectSector(byte sector, MifareUltralight mifareUltralight) throws IOException {
    if (mifareUltralight.isConnected()) {
        mifareUltralight.close();
    }

    // SECTOR_SELECT command (see nxp p. 46)
    byte[] sectorSelectCmdPacket1 = new byte[2];
    byte[] sectorSelectCmdPacket2 = new byte[4];

    sectorSelectCmdPacket1[0] = (byte) 0xc2; // Sector select command
    sectorSelectCmdPacket1[1] = (byte) 0xff;

    sectorSelectCmdPacket2[0] = sector; // Memory sector to be selected; 1 for I2C 2k version
    sectorSelectCmdPacket2[1] = (byte) 0x00;
    sectorSelectCmdPacket2[2] = (byte) 0x00;
    sectorSelectCmdPacket2[3] = (byte) 0x00;

    mifareUltralight.connect();

    try {
        // ACK = 0A
        byte[] sectorSelectResp1 = mifareUltralight.transceive(sectorSelectCmdPacket1);
        Log.w(TAG, bytesToHex(sectorSelectResp1));
    } catch (IOException e) {
        Log.w(TAG, "selectSector: there was an exception while sending first sector select command");
        e.printStackTrace();
    }

    try {
        mifareUltralight.transceive(sectorSelectCmdPacket2);
        Log.w(TAG, "Second sector select command sent");
    } catch (IOException e) {
        Log.w(TAG, "selectSector: there was an exception while sending second sector select command");
        e.printStackTrace();
    }

    mifareUltralight.close();
}

当我调用selectSector方法时,第一个收发完成但第二个收不到,导致错误

  

android.nfc.TagLostException:标签丢失了。

如何在不获取TagLostException的情况下选择和操作扇区?

1 个答案:

答案 0 :(得分:0)

SECTOR_SELECT命令的第二阶段导致TagLostException是正常的。这在许多Android设备上发生,并且是由SECTOR_SELECT命令的第二阶段确认的方式(被动ACK)引起的。收到该特定命令的例外后,您可以安全地继续与标记通信。只有当您收到TagLostException的命令时,如果您希望有明确的ACK /响应数据,那么通信就会出现问题。

另请注意,选择扇区后应关闭连接,因为这会重置某些Android设备上的标记。因此,以后重新连接标记时可能不再选择该扇区。

典型的扇区选择方法如下所示:

public boolean selectSector(int sector) throws IOException {
    byte[] cmd_sel1 = { (byte)0xC2, (byte)0xFF };
    byte[] cmd_sel2 = { (byte)sector, (byte)0x00, (byte)0x00, (byte)0x00 };

    byte[] result1 = transceive(cmd_sel1);
    if (result1 == null) {
        throw new TagLostException();
    } else if ((result1.length == 1) && ((result1[0] & 0x00A) == 0x000)) {
        // NACK response according to DigitalProtocol
        return false;
    } else {
        try {
            byte[] result2 = transceive(cmd_sel2);
            if (result2 == null) {
                throw new TagLostException();
            } else if ((result2.length == 1) && ((result2[0] & 0x00A) == 0x000)) {
                // NACK response according to DigitalProtocol
                return false;
            } else {
                return true;
            }
        } catch (Exception e) {
            // passive ACK
            return true;
        }
    }
}