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ST25RU3993 - Reading and writing to an RFID tag at a word address greater than 0x7F fails.

shilparaju
Associate

Hallo!

With ST25RU3993 UHF RFID reader, reading and writing to an RFID tag via the ST commands CMD_WRITE_TO_TAG and CMD_READ_FROM_TAG at a word address greater than 0x7F fails.

Using CMD_GENERIC_CMD, I could successfully read from the tag even beyond word address 0x7F (by manually providing the address in the EBV format).

But write to tag using CMD_GENERIC_CMD is still a problem

  

According to EPC Class1 Gen2 spec, Writing to a tag involves two steps :

      1. Random Number Request (Gen2 command - Req_RN)

      2. Write to tag (Gen2 command - Write) -- actual data to be written into tag has to be ex-ored with the random number received

 But, the actual value written into the tag is different from the requested value.

As a means to use CMD_GENERIC_CMD for writing to tag, I first want to succeed with a word address below 0x7F.

An example, where I try to use CMD_GENERIC_CMD to write FF FF to a tag at word address 0x00 00

Req_RN replies with a random number RN16 :      BD 97

Actual value to be written to the Tag is           FF FF

Value sent via CMD_GENERIC_CMD Write       BD 97 ^ FF FF = 42 68

After successful write RN16 received 05 28

Value actually written on the tag              47 40 ( which is strangely 42 68 ^ 05 28 )

output from ST Log:

OKAY: Send command ff, return value %2

OKAY: Send command ff, returned bd974e67

OKAY: Send command ff-c3-c0-10-9a, return value %2

OKAY: Send command ff-c3-c0-10-9a, returned 05289fbf

I see that for every command RN16 and CRC are handled by the firmware itself.

Requesting your feedback on this behaviour and a solution to read and write at word addresses beyond 0x7F

Thank you!

Regards,

Shilpa

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