Different UIDs on iOS / Android with ISO15693 Tag

I’m using the following code to read out the UID in iOS / Android within an ionic app. With the most NFC Tags everything is working as expected.

But with ISO15693 Tags I get the wrong UID for iOS. I checked the UID with the iOS/Android App NFC-Tools. There both UIDs are the same.

With the plugin I get an other UID. Any Idea, what I am doing wrong?

if (this.platform.is('ios')) {
  // Handling iOS
  try {
    const nfcTag = await this.nfc.scanTag();
    return this.nfc.bytesToHexString(nfcTag.id);
  } catch (e) {
    // ...
  }
} else {
  // Handling Android
  return new Promise((resolve, reject) => {
    let flags = this.nfc.FLAG_READER_NFC_A | this.nfc.FLAG_READER_NFC_V;
    const subscription = this.nfc.readerMode(flags).subscribe(
      nfcTag => {
        const uid = this.nfc.bytesToHexString(nfcTag.id);
        subscription.unsubscribe();
        resolve(uid);
      },
      err => {
        // ...
      }
    );
  });
}

Example for the same ISO15693 Tag:

// ios
// Raw: [224, 4, 1, 80, 118, 210, 129, 5]
// nfc.bytesToHexString: e004015076d28105

// android
// Raw: [5, -127, -46, 118, 80, 1, 4, -32]
// nfc.bytesToHexString: 0581d276500104e0

Thanks

[aaronbach]

I wrapped my code with the following function to gather the correct uid. Not every NFC-tag used with our app is ISO conform, so I think the function should do the trick:

getUid (byteArray: number[]) {
  const uid = this.nfc.bytesToHexString(byteArray);
  // If UID is not starting with 'e0' => reverse the byte array
  if (uid.substr(0, 2).toLowerCase() !== 'e0') {
    const revUid = this.nfc.bytesToHexString(byteArray.reverse());
    if (revUid.substr(0, 2).toLowerCase() === 'e0') {
      return revUid;
    }
  }
  return uid;
}

thank you @erikm30

[mameier]

As the lower 6 Byte are simply a serial number, and the standard does’n mention that 0x0E is forbidden as last byte of the serial number, probaly every 256th ID might be misinterpreted.

It’s better to check the os. If its Android, reverse the bytes.