Get nfc tag uid

[quocnguyen123]

How can i get uid (unique ID) of NFC tag? Help me please!

[pokusew]

Hi @quocnguyen123,

in order to get UID of NFC tag, you need to send an appropriate APDU command (Get Data in this case, btw you can find some basic commands here) using reader.transmit method and then parse the response.

You can do it like this:

// ... connection to the reader and detecting card code as shown in README

// APDU CMD: Get Data
const packet = new Buffer([
  0xff, // Class
  0xca, // INS
  0x00, // P1: Get current card UID
  0x00, // P2
  0x00  // Le: Full Length of UID
]);

reader.transmit(packet, 12, (err, response) => {

  if (err) {
    console.log(err);
    return;
  }

  if (response.length < 2) {
    console.log(`Invalid response length ${response.length}. Expected minimal length was 2 bytes.`);
    return;
  }

  // last 2 bytes are the status code
  const statusCode = response.slice(-2).readUInt16BE(0);

  // an error occurred
  if (statusCode !== 0x9000) {
    console.log('Could not get card UID.');
    return;
  }

  // strip out the status code (the rest is UID)
  const uid = response.slice(0, -2).toString('hex');
  // const uidReverse = reverseBuffer(response.slice(0, -2)).toString('hex'); // reverseBuffer needs to be implemented

  console.log('card uid is', uid);

});

---

If you don't want to deal with these underlying things, take a look at nfc-pcsc library. It offers easy to use high level API for detecting, reading and writing NFC tags and cards, also supports Promises and async/await.
You just need a few lines to read card UID.

Hope it helps.

[quocnguyen123]

I solved this issue with your direction. Thank you very much
In line: reader.transmit(packet, 12, (err, response) I think we should pass protocol as third argument.

[martinpaljak]

You should set the protocol, if needed, during connect. https://github.com/martinpaljak/esteid.js/blob/master/node-pcsc.js#L82