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Is it possible to change the gain on an Adafruit PN532 board?

I need to LIMIT the range in order for it to NOT interfere with another PN532 installed close by.

The board is to be used with an Arduino.

I've looked through the Library but can't find any settings to change the gain. Also looked at other libraries forked from the original Adafruit lib.

I know that MRFC522 has some settings to control the gain, and I was hoping to find something similar with the PN532.

EDIT: The datasheet can be found here: https://cdn-learn.adafruit.com/downloads/pdf/adafruit-pn532-rfid-nfc.pdf

In the PDF there is a link to the schematics. It can be found here: https://cdn-learn.adafruit.com/assets/assets/000/009/729/original/PN532_Breakout_Schematic_v1.0.pdf?1374440547

And - the most detailed information about the PN532 board I could find, is located here: https://cdn-shop.adafruit.com/datasheets/PN532_AntennaDesign_v1.0.pdf

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    \$\begingroup\$ What's an Adafruit PN532 board? \$\endgroup\$
    – Andy aka
    Mar 6, 2019 at 12:23
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    \$\begingroup\$ At the very least you should link the datasheets to these parts you are talking about \$\endgroup\$
    – MCG
    Mar 6, 2019 at 12:28
  • \$\begingroup\$ Sorry. Kind of new here and to electronics in general. But I'll try to find what you are asking for. I'll update the question with the information I can find. \$\endgroup\$
    – public-profile
    Mar 6, 2019 at 12:43

1 Answer 1

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If a permanent change is OK, you can modify the antenna matching circuit to reduce the gain and thus the range. Here's the relevant part of the schematic:

enter image description here

The simplest way is to increase R3 and R4 to about 2-3 Ohm, which will reduce the Q-factor. Or, if you have the patience and the tools, you can re-implement the entire circuit according to this application note with the correct Q-factor and lower gain.

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  • \$\begingroup\$ Thanks! I think changing the two resistors would be the preferred way to go. Re-implementing the circuit is way over my head. :-D \$\endgroup\$
    – public-profile
    Mar 6, 2019 at 13:09

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