MFRC631 and MiFare Ultralight

[Consul]

Dear all,

I'm using the NXP MFRC631 Reader with a MiFare Ultralight Tag, and experience some problems. In my Application there will be only one card in the HF-Field, ie no collision will ever occur. I'm communicating With the MFRC631 by means of a SPI Interface to a microcontroller. The communicaton sequence with the Tag is based on a script from NXP. The original script was written for reading a 4 byte (single) UID from a 14443-A TAG, with only one Tag in HF-Field. This Works perfekt, ie I activate Tag with ReqA and receive the ATQA. I then issue the SEL 93 and NVB 20, and correctly receive "88 UID0 UID1 UID2 BCC", ie first 3 UID bytes of a double (7 byte) UID. So far so good :).

The problem start when I try to read out the remaining last 4 UID bytes.. After Reading the ISO/IEC 14443-3 document I tried simply to issue a SEL 95 and NVB 20 sequence, to get the last UID bytes from cascade Level 2, but in response no UID data was to read from the MFRC631 FIFO. After further Reading I tried to send "SEL 93, NVB 70, 88, UID0, UID1, UID2, BCC" to receive a SAK (with expected value 04). And then send "SEL 95 and NVB 20" to read out the remaining 4 UID bytes, from cascade Level 2. Still no data to read out from 631 FIFO..

Can someone please guide me in the right direction here?

Thanks :-)

UPDATE:
I solved this: I was missing RX and TX CRC when I selected cascade level 2.
Thanks,
Consul

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