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Eyzeryong
Graduate
January 10, 2025
Solved

ST25R95 detect ST25D tag

  • January 10, 2025
  • 2 replies
  • 1592 views

I use ST25R95 to detect the ST25D tag. I keep the tag on the antenna of the Reader all the time, and some situations have occurred.

Hi

Even if I place it precisely on it all the time, the tag may not be read probabilistically during detection. Is this normal? The antenna fails to read the tag about two or three times out of ten readings.

Please help me,thanks~

 

    This topic has been closed for replies.
    Best answer by Blake_Victor

    Hi,

    Based on your inductance value of 0.46uH, I populated the respective values from your design into the Excel calculation tool, and this is what I obtained:

     

    Blake_Victor_1-1737116548330.png

    Following the steps from the application note, I replaced the inductance value, and the chart looks like this:

    Blake_Victor_2-1737116578300.pngBlake_Victor_3-1737116584937.png

     

    From your matching network, try to modify the following:

    • C18 + C19 = 270pF
    • C16, C21 = 56pF
    • BC1, BC2 = 280nH
    • C20, C17 = 200pF

    The tuning frequency can be adjusted using C2, and the impedance magnitude can be adjusted using C11/C12.

    BR,

    BV

     

    2 replies

    B
    Brian TIDAL
    Technical Moderator
    January 10, 2025

    Hi,

    do you use your own custom board or one of the ST demo boards (if yes, which one)? 

    What is the sequence of command being sent and what is the return code in case of failure? I would suggest to connect a logic analyzer on SPI + IRQ_IN and IRQ_OUT and provide the trace file.

    Rgds

    BT

    E
    EyzeryongAuthor
    Graduate
    January 14, 2025

    Hi, 

        thanks for your answer~

       I use own custom board, and ues ISO15693,send these define:

    ISO15693_REQFLAG_SINGLESUBCARRIER,
    ISO15693_REQFLAG_HIGHDATARATE,
    ISO15693_REQFLAG_INVENTORYFLAGSET,
    ISO15693_REQFLAG_NOPROTOCOLEXTENSION,
    ISO15693_REQFLAG_NOTAFI,
    ISO15693_REQFLAG_1SLOT,
    ISO15693_REQFLAG_OPTIONFLAGNOTSET,
    ISO15693_REQFLAG_RFUNOTSET

    by 0x04 SendRecv cmd

    sometimes host return me 0x87 Frame wait time out or no tag,but I still put the tag on the antenna，I've been aiming at it all the time,I don't know why....,

    I am sorry that I haven't the logic analyzer,so I couldn't offer you more about SPI + IRQ_IN and IRQ_OUT

    I use 0x09046801011D to initialize ISO15693

     

    B
    Brian TIDAL
    Technical Moderator
    January 14, 2025

    Hi,

    This is probably due to a matching circuit issue on the custom board. Make sure to follow the "Step by step procedure" described in the Application Note AN5248 (ST25R95 transceiver antenna tuning circuit with EMI filter) to properly tune the matching circuit.

    Rgds

    BT

      E
      EyzeryongAuthor
      Graduate
      January 15, 2025

      Hello

      I have download the ST25R95 EMI FILTER CALCULATION.xlsm,but I observed that I'm a little bit unproductive

      Eyzeryong_0-1736904821332.png

      This is my part of the schematic, could you help me take a look, thank you so much

       

      B
      Blake_Victor
      ST Employee
      January 16, 2025

       

      Hi,

      Based on the antenna parameter you defined (0.48uH), different Low Pass Filter values and some tuning in the matching circuit are required.

      According to your inductance value, try adapting similar Low Pass Filter values as described in the Application Note: AN5248.  Additionally, tune the capacitance values of C11, C12, and C2 to achieve a similar impedance chart as shown below:

      Blake_Victor_0-1737040766448.png

      I hope this helps with your matching circuit.

      Regards,

      BV

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