javaandroidnfcrfidiso-15693

Writing Tags with NfcV tag.transceive

I'm working on an application about NFC writing. Lets call it Writer... I am writing data to a NfcV tag.

The string I am trying to write is String test = "this is\ta real\ttestcase\tyou tag";

To write data I'm using NfcV's transceive method. So this is my writer-method: 

public static String bytesToHex(byte[] bytes) {
    StringBuilder sb = new StringBuilder(bytes.length * 2);
    Formatter formatter = new Formatter(sb);
    for (byte b : bytes) {
        formatter.format("%02X", b);
    }
    formatter.close();
    return sb.toString();
}

public void write(View v) {
    try {
        String[] tagInfoArray = new String[tagData.size()];
        for (int i = 0; i < tagData.size(); i++)
            tagInfoArray[i] = tagData.get(i).getText().toString();

        String tagInfo = join(tagInfoArray, "\t");
        //String test = "this is\ta real\ttestcase\tyou tag";
        writeTag(tag, tagInfo);
    } catch (NullPointerException e) {
        Toast.makeText(this, "How about providing a tag!",
                Toast.LENGTH_LONG).show();
    } finally {
        write.setBackgroundResource(R.layout.bluebutton);
    }
}

public String join(String[] input, String delim) {
    String output = "";
    if (input.length > 0)
        output += input[0];
    if (input.length > 1)
        for (int i = 1; i < input.length; i++)
            output += delim + input[i];
    return output;
}

public void exitButton(View v) {
    this.foreground.disableForeground();
    System.exit(0);
}

public void writeTag(Tag tag, String data) {
    NfcV myTag = NfcV.get(tag);
    try {
        myTag.connect();
        if (myTag.isConnected()) {
            byte[] info = data.getBytes();
            int dataLength = info.length;
            if (data.length()/4 <= 64){ 
                byte[] args = new byte[15];
                args[0] = 0x20;
                args[1] = 0x21;
                byte[] id = tag.getId();
                for (int o=0; o<8; o++)
                    args[o+2] = id[o];
                for (int i = 0; i<64; i++) {
                    args[10] = (byte) i;
                    args[11] = 0x00;
                    args[12] = 0x00;
                    args[13] = 0x00;
                    args[14] = 0x00;
                    byte[] out = myTag.transceive(args);
                    String out2 = bytesToHex(out);
                    System.out.println("1:.. " + printHex(out2));
                }
                for (int i = 0; i<=dataLength/4; i++) {
                    args[10] = (byte) i;
                    args[11] = getByte(info, (i*4)+0);
                    args[12] = getByte(info, (i*4)+1);
                    args[13] = getByte(info, (i*4)+2);
                    args[14] = getByte(info, (i*4)+3);
                    byte[] out = myTag.transceive(args);
                    String out2 = bytesToHex(out);
                    System.out.println("2:.. " + printHex(out2));
                }
            }
        }
    } catch (IOException e) {
        System.out.println(e.getMessage());
    } finally {
        if (myTag != null) {
            try {
                myTag.close();
            } catch (IOException e) {
                System.out.println(e.getMessage());
            }
        }
    }
}

public static byte getByte(byte[] input, int key){
    try {
        return input[key];
    } catch (Exception e){
        return (byte)0x00;
    }
}

public String printByte(byte[] input){
    try {
        return new String(input, "UTF-8");
    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return "";
}

public String printHex(String input){
    return input;
}

So when im writing stuff the outcome is not what I am expecting it to be. It's either not writing at all, or just writing parts, while not overwriting, what has been on the tag before.

This is the output:

11-05 15:32:33.139: I/System.out(1390): 1:.. 00
11-05 15:32:33.249: I/System.out(1390): 1:.. 00
11-05 15:32:33.349: I/System.out(1390): 1:.. 00
11-05 15:32:33.449: I/System.out(1390): 1:.. 00
11-05 15:32:33.549: I/System.out(1390): 1:.. 00
11-05 15:32:33.649: I/System.out(1390): 1:.. 00 
11-05 15:32:33.759: I/System.out(1390): 1:.. 00
11-05 15:32:33.859: I/System.out(1390): 1:.. 00
11-05 15:32:33.959: I/System.out(1390): 1:.. 00
11-05 15:32:34.059: I/System.out(1390): 1:.. 00
11-05 15:32:34.159: I/System.out(1390): 1:.. 00
11-05 15:32:34.259: I/System.out(1390): 1:.. 00
11-05 15:32:34.359: I/System.out(1390): 1:.. 00
11-05 15:32:34.469: I/System.out(1390): 1:.. 00
11-05 15:32:34.569: I/System.out(1390): 1:.. 00
11-05 15:32:34.669: I/System.out(1390): 1:.. 00
11-05 15:32:34.769: I/System.out(1390): 1:.. 00
11-05 15:32:34.869: I/System.out(1390): 1:.. 00
11-05 15:32:34.979: I/System.out(1390): 1:.. 00
11-05 15:32:35.079: I/System.out(1390): 1:.. 00
11-05 15:32:35.179: I/System.out(1390): 1:.. 00
11-05 15:32:35.289: I/System.out(1390): 1:.. 00
11-05 15:32:35.389: I/System.out(1390): 1:.. 00
11-05 15:32:35.489: I/System.out(1390): 1:.. 00
11-05 15:32:35.589: I/System.out(1390): 1:.. 00
11-05 15:32:35.689: I/System.out(1390): 1:.. 00
11-05 15:32:35.789: I/System.out(1390): 1:.. 00
11-05 15:32:35.889: I/System.out(1390): 1:.. 00
11-05 15:32:35.989: I/System.out(1390): Transceive failed
Solution

  • To summarize the various issues in the initial post: