Writing to a Mifare tag with Android NFC?

Question

I am trying to write a simple "Hello World" line in the first block of sector 0 on a Mifare 1K tag. The tag is brand new with default configuration. Trailer sector (block 3) when reading: 00 00 00 00 00 00 00 00 ff 07 80 69 ff ff ff ff ff ff ff ff . Therefore, the access conditions are ff 07 80 69 , that is, I can read and write on each block using the A key.

However, I cannot write anything in the tag. Here is my code:

 try { mfc.connect(); boolean auth = false; auth = mfc.authenticateSectorWithKeyA(0,MifareClassic.KEY_DEFAULT); if (auth) { String text = "Hello, World!"; byte[] value = text.getBytes(); byte[] toWrite = new byte[MifareClassic.BLOCK_SIZE]; for (int i=0; i<MifareClassic.BLOCK_SIZE; i++) { if (i < value.length) toWrite[i] = value[i]; else toWrite[i] = 0; } mfc.writeBlock(0, toWrite); } 

I get the following exception: Transceived failed .

What am I doing wrong?

Here's the stack trace:

 07-09 00:19:44.836: W/System.err(13167): at android.nfc.TransceiveResult.getResponseOrThrow(TransceiveResult.java:52) 07-09 00:19:44.843: W/System.err(13167): at android.nfc.tech.BasicTagTechnology.transceive(BasicTagTechnology.java:151) 07-09 00:19:44.843: W/System.err(13167): at android.nfc.tech.MifareClassic.writeBlock(MifareClassic.java:453) 07-09 00:19:44.843: W/System.err(13167): at com.example.andorid.apis.mifare.MainActivity.resolveIntent(MainActivity.java:128) 07-09 00:19:44.843: W/System.err(13167): at com.example.andorid.apis.mifare.MainActivity.onNewIntent(MainActivity.java:275) 07-09 00:19:44.843: W/System.err(13167): at android.app.Instrumentation.callActivityOnNewIntent(Instrumentation.java:1123) 07-09 00:19:44.843: W/System.err(13167): at android.app.ActivityThread.deliverNewIntents(ActivityThread.java:2041) 07-09 00:19:44.843: W/System.err(13167): at android.app.ActivityThread.performNewIntents(ActivityThread.java:2054) 07-09 00:19:44.843: W/System.err(13167): at android.app.ActivityThread.handleNewIntent(ActivityThread.java:2063) 07-09 00:19:44.843: W/System.err(13167): at android.app.ActivityThread.access$1400(ActivityThread.java:122) 07-09 00:19:44.843: W/System.err(13167): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1193) 07-09 00:19:44.851: W/System.err(13167): at android.os.Handler.dispatchMessage(Handler.java:99) 07-09 00:19:44.851: W/System.err(13167): at android.os.Looper.loop(Looper.java:137) 07-09 00:19:44.851: W/System.err(13167): at android.app.ActivityThread.main(ActivityThread.java:4340) 07-09 00:19:44.851: W/System.err(13167): at java.lang.reflect.Method.invokeNative(Native Method) 07-09 00:19:44.851: W/System.err(13167): at java.lang.reflect.Method.invoke(Method.java:511) 07-09 00:19:44.851: W/System.err(13167): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 07-09 00:19:44.851: W/System.err(13167): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 07-09 00:19:44.851: W/System.err(13167): at dalvik.system.NativeStart.main(Native Method) 

Answer 1

You are trying to write block 0, which is not possible. Block 0 is always read-only, even access conditions say that it is writable. Block 0 maps the UID and some other manufacturer data. Try writing to block 1 or 2 and see if you have the same problem.

Answer 2

I saw this specific exception when trying to read from a tag that is no longer connected to the reader.

I know that for some card / reader combinations it is difficult to maintain a decent connection.

For example, my Nexus S has problems maintaining a connection with some tags. Nexus S does not have the strongest field. I think the Galaxy Note is similar in this regard.

Try other brand tags as well as other readers.

In addition, I will try to start reading through the for loop to find out if it supports the connection, if that makes sense.