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TRF7970A: Issues with implementing ISO 15693 anti-collision

Part Number: TRF7970A
Other Parts Discussed in Thread: MSP-EXP430G2ET

Hello All,

I'm having issues with implementing ISO 15693 anti-collision.  I'm using a TRF7970A NFC transceiver BoosterPack.   I'm using 16 slots as a parameter when sending the inventory command.

The serial numbers of the tags that I'm working with do not collide with each other. So far I can get it the anti-collision algorithm to work, but when dealing with tags in the last slot it does a weird behavior.  Every other try of anti collision fails. When it fails, I don't receive a No response IRQ after sending the inventory command.

Anyone experience this before?  Any suggestions on what to look for?

Thank you,

Scott

  • Hello Scott,

    I have not seen such issues before.

    If the number of tags becomes too big then there are also physical limitations of the system are becoming relevant.

    Too many tags in close distance to each other can cause a de-tuning of their antennas, which has an impact on the read range.

    Since the tags are getting powered from the reader field there is also a limitation in how many tags can be powered simultaneously.

    Can you please check these aspects and let me know if these limitations are not met?

    Best regards,

    Andreas.

  • Hi Andreas,

    Thank you for your reply and thank you for your time.

    So after playing around with the tags and code:

    • I can consistently get this weird behavior with a single tag in the readers field so long as the tag's serial number ends with a 'F' (example xFxxxx...E0)
    • Does not matter how far or how close the tag is.
    • Currently, after the transmitting the next slot command, I transmit a stop decoders command and disable the slot counter. However, if I do an additional transmit next slot command (so I'm issuing a total of 16 next slot commands), it actually fixes this problem.

    If I sort out my tags with 'F' at the end of the serial number, the reader work fine and  I can see around 8.

    There must be something in code that I'm not doing correctly. Maybe a setting is not correct? Maybe the commands I'm issuing is not in the correct order?

    I'm using Sloa138 and the iso15693.c file in sloc297c as reference for my code.  I might be missing a detail, so any guidance is greatly appreciated.

    Thank you,

    Scott

  • Hello Scott,

    it is hard to judge on any software misbehavior. As you mention the issue might be hidden in a detail. But would it be an option for you to compare against the original solution?

    Means, purchase an MSP-EXP430G2ET and run the original FW sloc297 and then compare and debug from there?

    Best regards,

    Andreas.