Reading NDEF-Message using PN532

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  • Hi,

    I would like to create an NFC tag reader using a PN532. In the end I would like to read NDEF messages from any NDEF tag.

    The general interfacing already works. I wired up the MDBT42Q breakout and a PN532 breakout board.

    Using the PN532 module I am able to read the card id, as it's shown in the tutorial.

    Now, I would like to read all bytes and parse an NDEF message with the library https://github.com/andijakl/ndef-nfc/.

    The idea is to read all bytes of the NDEFMessage and then parse them with the following call:

    var ndefMessage = NdefLibrary.NdefMessage.fromByteArray(by­teArray);
    

    I managed to load the minified version of the library within espruino, I just need to read all the bytes of the tag.
    So I started modifying the PN532 module in an own fork and created the function findCardsAllBytes, which looks like this:

    PN532.prototype.findCardsAllBytes = function(callback) {
      this.cmd([C.PN532_COMMAND_INLISTPASSIVET­ARGET,
                 1, // max targets (max=2)
                 C.PN532_BRTY_ISO14443A // modulation type
                ]);
      var p = this;
      setTimeout(function() { // wait for NFC poll (30ms)
        var d = p.i2c.readFrom(C.PN532_I2C_ADDRESS, 20+1).slice(1);
        if (d[6]==C.PN532_COMMAND_INLISTPASSIVETARG­ET+1) {
          if (d[7]!=1) print("Expecting 1 tag, got "+d[7]);
          callback(d);
        }
      }, 30);
    };
    

    Do you have an idea which I2C commands I need to read all the raw bytes of the tag?

    Thank you!
    Martin

  • Hi Martin,

    I'm afraid I don't personally, but maybe looking at another library would help. For example Adafruit have a library, and if you're reading mifare (example at https://github.com/adafruit/Adafruit-PN5­32/blob/master/examples/readMifare/readM­ifare.ino) they seem to authenticate and then read, which both seem to be done with PN532_COMMAND_INDATAEXCHANGE:

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Reading NDEF-Message using PN532

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