CR95HF communication with ST25TA02KB-D, why the RATS command fail to answer ?

[JRoud.1]

Hello,

I'm new to RFID and I have troubles with the RATS command of the ISO-14443 standard. I am currently working with a CR95HF (reader) and a ST25TA02KB-D (tag). The uC driving the reader is an Arduino UNO, this part is working fine so far.

My issue is that I can't manage to have an answer from the tag when sending the RATS command. The error I get is the 87 : "Frame wait time out" according to the reader datasheet.

I found similar issues and the main culprit seems to be the Frame Waiting Time :

Link 1

Link 2

Link 3

But even with this parameter set to 10ms I can't get a valid answer to the RATS command.

Here is a capture of the data exchange between the Arduino UNO and the CR95HF until the RATS command :

Protocol selection (FDT = 10ms) :

>>> 00 02 05 02 00 00 21 00

<<< 00 00

REQA :

>>> 00 04 02 26 07

<<< 80 05 42 00 28 00 00

ANTICOLLISION (there is only one tag in the reader field) :

>>> 00 04 03 93 20 08

<<< 80 08 88 02 E3 00 69 28 00 00

SELECT :

>>> 00 04 08 93 70 88 02 E3 00 69 28

<<< 80 06 04 DA 17 08 00 00

RATS :

>>> 00 04 03 E0 50 28

<<< 87 00

Since I am a newbie in RFID, is there an obvious error that I made in the reader/tag exchange ?

I tried with higher FDT value and even another tag type (LXMS33HCNK-171) but I still have this error.

Any advice to what I could try to overcome this issue ?

My end goal is to access the NDEF user memory and the tag's counter.

Thanks,

JR

[Brian TIDAL · Accepted solution]

Hello Jérôme,

in your trace, the reply to SELECT Cascade Level 1 (93 70 88 02 E3 00 69) is 04 which mean UID non complete (see 80 06 04 DA 17 08 00 00). As the ST25TA02KB has a 7-byte unique identifier (UID), ANTICOLLISION Cascade Level 2 (95 20) has to be performed to retrieve the 3 remaining bytes of the UID after SELECT Cascade Level 1 where only the first 4 bytes have been found (02 E3 00 69). As you tag has not been "fully" selected, it cannot answer to the RATS.

I would suggest to use ST25 RFAL library that implements the full collision resolution, the ISO-DEP protocol. See https://github.com/stm32duino/X-NUCLEO-NFC03A1 for a port on top of STM32 nucleo board (I believe some adaptations will be needed for your Arduino UNO board).

Rgds

BT

[JRoud.1]

Nice, now it works :

ANTICOLLISION CL1 :

>>> 00 04 03 93 20 08

<<< 80 08 88 02 E3 00 69 28 00 00

SELECT CL1 :

>>> 00 04 08 93 70 88 02 E3 00 69 28

<<< 80 06 04 DA 17 08 00 00

ANTICOLLISION CL2 :

>>> 00 04 03 95 20 08

<<< 80 08 1E B2 7B 9A 4D 28 00 00

SELECT CL2 :

>>> 00 04 08 95 70 1E B2 7B 9A 4D 28

<<< 80 06 20 FC 70 08 00 00

RATS :

>>> 00 04 03 E0 50 28

<<< 80 0A 05 75 80 60 02 BB 58 08 00 00

Thank you it was indeed the missing cascade level 2 !

I am exploring the GIT repository for the remaining steps I need to achieve.