TRF7970A: Communicating with Android

Update:

So, I just used the NFC TI tool with a connected DLP-7970ABP and I was able to detect the android phone. So, I'm assuming that the ISO14443A 3 & 4 are being executing successfully. The FW I have written also succeeds with these two processes. Where it's failing is receiving response data to the initial ISO7816 Select File command. Below is the code I've written for that specific command:

uint8_t Iso7816Commands__IsoSelectFile(uint8_t p2, uint16_t fileId, uint8_t *dfName, uint8_t dfSize)
{
   uint8_t status = ERROR;         /* Initialize return status */
   uint8_t bufSize = 0x00;            /* Number of bytes to be transmitted to TRF FIFO */
   uint8_t *buf = nfc_data.buf;      /* TRF FIFO data buffer */

   buf[bufSize++] = 0x8F;
   buf[bufSize++] = 0x93;  /* Delayed transmit with CRC */
   buf[bufSize++] = 0x3D;

   /* Calculate the number of bytes the TRF has to send to the tag */
   uint16_t numBytes = 0x0006 + dfSize;
   buf[bufSize++] = (uint8_t) ( numBytes >> NIBBLE );
   buf[bufSize++] = (uint8_t) ( ( 0x000F & numBytes ) << NIBBLE );

   /* ISO/IEC 7816-4 C-APDU (Command Application Protocol Data Unit) */
   buf[bufSize++] = 0x00;  /* Standard ISO/IEC 7816-4 Command CLA must be 0x00 */
   buf[bufSize++] = ISO_SELECT_FILE_CMD; /* 0xA4 */
   buf[bufSize++] = 0x04; /* Select file using DF Name */
   buf[bufSize++] = p2;
   buf[bufSize++] = dfSize;   /* Length of data field */

   /* Populate Data Field & update the buffer size */
   memcpy(&buf[bufSize], &dfName[0], dfSize);
   bufSize += dfSize;
   buf[bufSize++] = LE;    /* Expected response length - 0x00 =  All available data */

   /* Transmit Command */
   Trf797x__RawWrite(&buf[0], bufSize);
   HAL_Delay(5);

   /* Wait for ISO/IEC 7816-4 R-APDU (Response APDU) response from tag */
   /* Timeout = 26 ms */
   WaitRxData(0x1A);
   HAL_Delay(5);

   /* Check if response arrived */
   if( Trf797x__GetState() == TRF797X_STATE_RX_COMPLETE )
   {
      sprintf(printBuf, "UID: %02X %02X %02X %02X %02X %02X %02X\r\n", buf[0], buf[1], buf[2], buf[3], buf[4], buf[5], buf[6]);
      printDebug(printBuf);
   }
   else
   {
      sprintf(printBuf, "ISO Select File Command error: %02X\r\n", Trf797x__GetState());
      printDebug(printBuf);
   }

   return status;
}

The issue ^ is that the response in never received.

Hello,

I am attempting to do this on my own system. The system needs to only support ISO 14443A type tags. I just used the TI NFC Tool to validate that detection of an android phone is possible with the TRF7970A. Using the FW I have written, I am able to send the command shown above to various DESFire cards and I'm capable of receiving a response. I'm just wondering what the reason could be that the when I try with an Android, the TRF does not pick up the response. The app I've written for it was tested and is working as it should using a different RFID transceiver.

Thank you so much!

It was the PCB byte!

Where can I find more information about this?

Is this PCB byte supposed to be added to the R-APDU as well - in the response sent by the Android device?

I'm still having trouble on the RX side. Would a different Direct mode need to be configured a long with CRC in the RX response?

Thanks so much for your reply. I managed to get it working. It seems like only some phones respond properly though.