Is it possible using TapLinx SDK to handle multiple tags?

Forum / MIFARE SDK / Is it possible using TapLinx SDK to handle multiple tags?

  • 6. January 2021 at 11:37
    Hi, We are new to TapLinx programming and facing a issue to distinguish a specific tag (NXP NTAG 424 DNA) from other ISO14443-ompilant tags in the field.

    Our App will run on Android phone, and using TapLinx seems to be a convenient way for us, that we don't have to deal with protocol commands like REQA, ANTICOLLISION (not matched UID), ANTICOLLISION command (matched UID), SELECT ... and so on.

    In NXP Application Note: AN10834 (MIFARE ISO/IEC 14443 PICC Selection) described how to Selecting the correct application in section 3, but that did not help us much, because we do not use the protocol commands.

    We also found an article: "Activating multiple Tags using NFC Reader Library" described how to activation each of NTAG216 when there are multiple tags in the field at a given index. But the article is using NFC Reader Library, not TapLinx, and we don't know whether this NFC Reader Library will be working on Android phone. The sample code in this article detected technology type and knew how many tags in the field.

    What we want to solve is to distinguish a NTAG 424 DNA tag in these situations:
    1. One NXP NTAG 424 DNA tag with two or more NTAG213 tags in the field
    2. One NXP NTAG 424 DNA tag with two or more other manufacturer's NFC Forum type 2 tags.
    3. Two or more NXP NTAG 424 DNA tags in the field, and we want to find a particular one.

    We also check the TapLinx Android API, only found a getSAK in interface IMFClassic, but because the TapLinx's sample code do not use getSAK(), so still we do not know how to use it (and maybe we should not use it?). Should this getSAK be used in a loop, and with each loop getSAK will return a tag's SAK, by this way we can get all tags' SAK?

    Is it possible using TapLinx SDK to solve our issues?

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    Re: Is it possible using TapLinx SDK to handle multiple tags?

    19. January 2021 at 14:25
    Dear Liang,

    TapLinx is designed for Android based devices with built-in NFC controller/reader.

    As from NFC Forum webpages:
    The NFC Controller connected with an antenna transmits and receives all NFC communication frames of the NFC Forum Device. NFC applications which are initiating and managing the NFC transactions are either:
  • apps located in the Device Host using the NFC API of the operating system inside the NFC Forum Device or
  • are
    located inside an optional available secure element directly connected to the NFC Controller.

  • To support the implementation of interoperable NFC Forum Devices, the NFC Forum has defined the NFC Controller Interface (NCI) between an NFC Controller and the Device Host of the NFC Forum Device.

    Activation (Technology polling loop, anti-collision) of the Tag / Card is done automatically by NFC Controller. Then NFC Controller passes gathered info to the Host system (OS). Just one Tag/Card (UID, Tech info etc.) is handled through Intents by Android "dispatch system", as described here.

    TapLinx is designed to handle only one tag at the time.

    Application note you are referring to, is meant for NFC controllers/readers on which Host application has full low level control over it.

    Best regards,
    The TapLinx team
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    Re: Is it possible using TapLinx SDK to handle multiple tags?

    29. January 2021 at 10:20
    Thank you very much, TapLinx Team:

    Yes, we want to handle one tag at a time, but because there could be at least two tags in fixed position within very closed range (none of them will be moved away), could we use TapLinx SDK to get the first tag, handling it, and then get second tag, handling it, and then third tag...?
    If we use TapLinx anti-collision API several times, and every time the API give us a different tag, we think it is possible to do so.
    (Correct us, if we are wrong.)

    If using high level TapLinx SDK could not achieve what we want, could the NFC Reader Library described in "NFC Activating multiple Tags using NFC Reader Library" article can be used with Android Phone to achieve what we want? If this Library can work well with Android Phone, we could invest resources to work on this.

    The ISO14443A anti-collision method is Bit Collision, we think if the reader send the same bit pattern to search for the tag every time, the tag responses first at the first time will also response first at the next time, in this situation, other tags in the field will never be selected.
    But the article ""NFC Activating multiple Tags using NFC Reader Library" tell us another story, it seems that the reader (or the application) after successfully get a tag's information (UID and type?), it will not stop and return, it can go on find another tags in the field, finally reader get all the tags' information in the field, reader (application) can decide which tag it wants to process.

    We wonder if the only solution is to use NFC Reader Library?

    We appreciate any help we can get. Thank you!

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