Writing data to Nexus 4 in card emulation mode with ACR122

Question

I am trying to send some data to Nexus 4 via NFC (i.e. card emulation mode). I tried several APDU commands, such as writing and updating APDUs, but I could not get them to work.

I'm trying to say that I want to send some data (not AID) to the phone after selecting the APDU command.

Thanks in advance,

Bader

Answer 1

The HCE emulated card will understand exactly the commands that your HCE application APDU service processes. So, for example, if your processCommandApdu() service processCommandApdu() service callback method looks like this:

 final static byte[] SW_NO_ERROR = new byte[]{ (byte)0x90, (byte)0x00 }; final static byte[] SW_INCORRECT_P1P2 = new byte[]{ (byte)0x6A, (byte)0x86 }; final static byte[] SW_INS_NOT_SUPPORTED = new byte[]{ (byte)0x6D, (byte)0x00 }; final static byte[] SW_ERR_UNKNOWN = new byte[]{ (byte)0x6F, (byte)0x00 }; @Override public byte[] processCommandApdu(byte[] apdu, Bundle extras) { if (apdu.length >= 4) { if ((apdu[1] == (byte)0xA4) && (apdu[2] == (byte)0x04)) { // SELECT APPLICATION return SW_NO_ERROR; } else if ((apdu[1] == (byte)0xCA) && (apdu[2] == (byte)0x02)) { // GET DATA (SIMPLE TLV) switch (apdu[3] & 0x0FF) { case 0x001: return new byte[]{ apdu[3], (byte)0x02, (byte)0x01, (byte)0x00, (byte)0x90, (byte)0x00 }; case 0x002: return new byte[]{ apdu[3], (byte)0x02, (byte)0x12, (byte)0x34, (byte)0x90, (byte)0x00 }; case 0x003: return new byte[]{ apdu[3], (byte)0x06, (byte)0xAA, (byte)0xBB, (byte)0xCC, (byte)0xDD, (byte)0xEE, (byte)0xFF, (byte)0x90, (byte)0x00 }; default: return SW_INCORRECT_P1P2; } } else { return SW_INS_NOT_SUPPORTED; } } return SW_ERR_UNKNOWN; } 

Your HCE application will understand the following APDU command:

• SELECT APPLICATION (by AID)

   00 A4 04 xx ... 

• GET DATA for data object 0201

   00 CA 02 01 00 

• GET DATA for data object 0202

   00 CA 02 02 00 

• GET DATA for data object 0203

   00 CA 02 03 00 

Other commands will lead to various errors.