ST25R3916B CRC Error

[AugustoZ]

Hi!

I'm using a x-nucleo-nfc08a1 board on a nucleo-g491re using mbed os, I'm trying to implement support for a tag which requires custom crc and parity on both tx and rx.

I'm using the following flags

RFAL_TXRX_FLAGS_CRC_TX_MANUAL | RFAL_TXRX_FLAGS_CRC_RX_KEEP | RFAL_TXRX_FLAGS_PAR_RX_KEEP | RFAL_TXRX_FLAGS_PAR_TX_NONE | RFAL_TXRX_FLAGS_CRC_RX_MANUAL

with rfalStartTransceive, tx works fine but rx fails with a crc error (rfalNfcDataExchangeGetStatus() returns RFAL_ERR_CRC.

rxRcvdLen gets set to 8192 and rxBuf is filled with 0s.

I'm using a proxmark3 to debug the nfc communication and the tag responds fine as expected, but RFAL (or the transceiver itself) drops the packet.

[Ulysses HERNIOSUS · Accepted solution]

Hi AugustoZ,

I find some code where we are using the following flags to exchange such frames:

 ctx.flags = RFAL_TXRX_FLAGS_CRC_TX_MANUAL | RFAL_TXRX_FLAGS_CRC_RX_KEEP | RFAL_TXRX_FLAGS_CRC_RX_MANUAL | RFAL_TXRX_FLAGS_NFCIP1_OFF | RFAL_TXRX_FLAGS_AGC_ON | RFAL_TXRX_FLAGS_PAR_RX_KEEP | RFAL_TXRX_FLAGS_PAR_TX_NONE;

Very similar to yours but looking at your description I find rfalStartTransceive (low level) mixed with rfalNfcDataExchangeGetStatus(higher level). The rfalNfc layer only supports byte oriented frames - did you hack into this layer?

Also the rxRcvdLen being set to 8192 shouldn't happen...

Best Regards, Ulysses

[AugustoZ]

Looks like the issue was indeed mixing low level with higher level. Using rfalGetTransceiveStatus fixed my issue. I also had some synchronization issues I fixed.

Thanks for the quick response!

Regards,

Augusto