RC522, ATQA and valid bits. Pls explain.

Haddock — Mon, 15 Jan 2024 10:40:41 GMT

I am using from beginning an arduino example converted to C. The MCU has a RC522 connected to it and using SPI as communication method. No collision handling or authentication is needed. The device only checks that the PICC can send its UID (it's a production test)

The call chain is: PICC_IsNewCardPresent -> PICC_RequestA -> PICC_REQA_or_WUPA(PICC_REQIDL 0x26) -> PCD_TransceiveData->PCD_CommunicateWithPICC

When I present a PICC near the RC522 i get a response. The FIFO reg reports that 2 bytes is in buffer (ATQA). I fetch the two bytes and the data is 0x0002. However, just after that I read register (CONTROLREG & 0x07) and that returns and set valid bits to 7. This function returns OK back to PICC_REQA_or_WUPA but that functions reports error because valid bits != 0.
Can anyone explain this valid bits issue? Do I need it?

FYI: I have three different PICC. The reponse is 0x002, 0x0004 and 0x0044 respective. I was thinking of using this ATQA to get the UID somehow - if that is possible. As I said, it will not be a collision with other PICC:s.

Re: RC522, ATQA and valid bits. Pls explain.

Ricardo_Zamora — Mon, 15 Jan 2024 18:08:49 GMT

Hello,

Are you using any Arduino library?

I apologize but MFRC522 is not recommended for new designs. For new designs, please use recommended product CLRC663 plus, so the support is limited.

Regards,

Ricardo

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RC522, ATQA and valid bits. Pls explain.

Re: RC522, ATQA and valid bits. Pls explain.