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TRF7970A: How to enable the external antenna keeping the freerun mode?

Part Number: TRF7970A

Tool/software:

I'm using this NFC reader and here there all the documents. It is based on TI TRF7970A transceiver.
Without issuing any command it works in freerun mode, reading out any NFC tag in the nearby. But it uses the internal antenna.

In the datasheet there is the command to switch to the external antenna:

Enable External Antenna: 01080003042B0000

But after that it seems the freerun mode is disabled, and I'm not able to detect tags anymore.

  • Hi,

    Enable External Antenna: 01080003042B0000

    But after that it seems the freerun mode is disabled, and I'm not able to detect tags anymore.

      Sorry, I'm not familiar with DLP-RFID2. My question would be if you have an external antenna connected? What is the external antenna looked like?

  • Of course I have the external antenna connected. I bought this model: https://www.mouser.it/ProductDetail/815-AANI-FB-0028

    Anyway, I found a way to detect the tag manually. I had hard time since the TI GUI is very buggy and very often hangs and I have to disconnect and reconnect the USB cable. But then I collected all the needed commands to manually retrieve a tag:

    > 01080003042B0000
    > 010A0003041001210000
    > 010C00030410002101090000
    > 0109000304F0000000
    > 0109000304F1FF0000
    > 0109000304A0010000

    The internal antenna was able to detect tags (ISO 14443A) at only 2-3 mm and often with wrong information. The external antenna is able to detect up to 20 mm. The UID seems correct in that range (even if sometimes the REQA returns nothing) but the second field changes, i.e.:

    > [637AD40CC1,41]

    > [637AD40CC1,40]

    > [637AD40CC1,42]

    not sure what does it mean, though.

    Is there a way to increase a little the range changing some register? I tried to toggle the AGC but it seems it changes nothing.