MFRC522 NFC transceiver support for Write16Bytes #2027
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Mifare WRite16Bytes, which is used by Mifare Classic and Mifare Ultralight (where it is called "compatibility write") requires two writes to the card. The first one transfers the block number, and the second contains the data to be written. Changed the Transceive function to handle Write16Bytes the same as counter increment, decrement, and restore (which also require two writes to the card).
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Ellerbach
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Feb 6, 2023
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Mifare's Write16Bytes command, which is used by Mifare Classic and Mifare Ultralight (where it is called "compatibility write") requires two writes to the card. The first one transfers the block number, and the second contains the data to be written. The Mfrc522 transceiver was not doing this, so writes to a Mifare Classic card always failed. Changed the Transceive function to treat Write16Bytes the same as counter increment, decrement, and restore (which also require two writes to the card).
In addition to renaming TwoStepsIncDecRestore to TwoStepsWrite16IncDecRestore, there were two issues in this method. First, the calculation of the CRC for the second transfer was incorrect. Second, it appears that the Mfrc522 actually returns a single byte response from the second transfer (which looks like the ACK/NAK), but dataFromCard.Length is 0, so SendAndReceiveData will return an error even though the write succeeded. Actual errors are already detected separately, so the simplest change is to pass NULL rather than dataFromCard. This makes dataFromCard unused, so it is removed from the method interface.
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