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Joseph Chan
Visitor II
February 17, 2018
Solved

Does anyone has good experience with the low power card detect feature in the real world environment?

  • February 17, 2018
  • 1 reply
  • 947 views
Posted on February 17, 2018 at 01:32

  1. In addition to detecting the credit card size tag, can it detect smaller tag such as the one like the size of a quarter reliably?
  2. Does it have false wake-up issue such as unexpected metal plate nearby or external radio source such as microwave oven, high power Access point, etc?

Thanks.

    This topic has been closed for replies.
    Best answer by Travis Palmer
    Posted on March 06, 2018 at 13:14

    Hi Joseph,

    The ST25R3911B has some features build in to overcome environmental changes in wake-up mode. 

    Automatic Averaging for example can be used to filter slow changing effects like temperature change or changing humidity. Only 'fast' changes like detuning by a tag or phone will be recognized.

    The delta-window is another setting that changes the sensitivity of the wake-up feature. It allows to set a range around the reference value, where no interrupt is triggered. 

    An interrupt can also be triggered by another device which operates at the same frequency range. A BLE or WIFI device is too different in terms of frequency to generate an amplitude change on the IC's input pins. A phone  which also sends out actively an HF field @ 13.56MHz will interfere with the inductive wake-up pulse and therefore also trigger an interrupt when being active in closer proximity. 

    BR Travis

    1 reply

    P
    Peter Boringer
    Visitor II
    February 19, 2018
    Posted on February 19, 2018 at 10:42

    Hi Joseph,

    I beleive that all the readers are ready to detect a tag with a quarter size of a credit card form factor with an antenna tuned  according to NFC/RFID standart/norma. Which type of pair Reader /Tag do you refer to?

    You second point is a bit generic can you please clarify your request and your setup?

    Thank
    J
    Joseph ChanAuthor
    Visitor II
    February 28, 2018
    Posted on February 28, 2018 at 22:16

    Hi Peter,

    Thanks for the reply. I have the ST25R3911B-DISCO and X-NUCLEO-NFC05A1 boards. I will experiment with different setup. The GUI is also useful.

    T
    Travis PalmerAnswer
    ST Employee
    March 6, 2018
    Posted on March 06, 2018 at 13:14

    Hi Joseph,

    The ST25R3911B has some features build in to overcome environmental changes in wake-up mode. 

    Automatic Averaging for example can be used to filter slow changing effects like temperature change or changing humidity. Only 'fast' changes like detuning by a tag or phone will be recognized.

    The delta-window is another setting that changes the sensitivity of the wake-up feature. It allows to set a range around the reference value, where no interrupt is triggered. 

    An interrupt can also be triggered by another device which operates at the same frequency range. A BLE or WIFI device is too different in terms of frequency to generate an amplitude change on the IC's input pins. A phone  which also sends out actively an HF field @ 13.56MHz will interfere with the inductive wake-up pulse and therefore also trigger an interrupt when being active in closer proximity. 

    BR Travis

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