Connecting to an external card with random UID

[plambrechtsen]

I'm currently playing around with the Nokia 6212 to see what NFC apps I can write for it.

Currently I am looking to read off an external card which is a nfc cashless card.

Using this code: Detect external ISO14443 card I can get it working in my phone.

However the card I am testing always responds with a random uid so I always get:

url: nfc:sc;type=iso4a;uid=08xxxxxx

So since the uid changes each time I am unable to connect to that card.

Any ideas what URL I should use to connect to the external device in range.

does anyone know if there is something similar to:

nfc:sc;type=iso4a;mode=external

to connect to the external in range nfc device no matter what UID it has?

[mroland]

No, there is no generic URL for external targets. You should not try to use a static URL for external targets.

Look at the example you cited:

public void targetDetected(TargetProperties[] targetProperties) {
  for (int i = 0; i < targetProperties.length; i++) {
    TargetProperties tp = targetProperties[i];

    (...)

    try {
      form.append("url: " + tp.getUrl(Class.forName(
            "javax.microedition.contactless.sc.ISO14443Connection"))
                          + "\n");
    } catch (Exception ex) {
      form.append(ex.toString());
    }

    (...)

}

You can retrieve the URL to the ISO14443Connection of your current target by calling the target properties' getURL() method:

tp.getUrl(Class.forName(
            "javax.microedition.contactless.sc.ISO14443Connection"))

This URL can be used with the Connector.open() method.

br,
Michael

[plambrechtsen]

No, there is no generic URL for external targets. You should not try to use a static URL for external targets.

Look at the example you cited:

public void targetDetected(TargetProperties[] targetProperties) {
  for (int i = 0; i < targetProperties.length; i++) {
    TargetProperties tp = targetProperties[i];

    (...)

    try {
      form.append("url: " + tp.getUrl(Class.forName(
            "javax.microedition.contactless.sc.ISO14443Connection"))
                          + "\n");
    } catch (Exception ex) {
      form.append(ex.toString());
    }

    (...)

}

You can retrieve the URL to the ISO14443Connection of your current target by calling the target properties' getURL() method:

tp.getUrl(Class.forName(
            "javax.microedition.contactless.sc.ISO14443Connection"))

This URL can be used with the Connector.open() method.

br,
Michael

Every time I try and use the Connector.open() method it says no such device.

This is because each time you connect to the device it returns a different UID.

I might try doing each poll of the token doing a .getUrl + open, but it seems less than ideal. Rather than getUrl + open + apdu... disconnect.

[mroland]

Every time I try and use the Connector.open() method it says no such device.

This is because each time you connect to the device it returns a different UID.

I'm not quite sure what you are trying to accomplish, but within one initialization cycle (i.e. field is on, anticollision has been performed) the UID of the device stays constant. Therefore, during the execution of the targetDetected callback the UID of the card stays constant, unless, of course, you remove the card from the phone's field again.

=> Within the targetDetected callback (or a thread spawned from it) you can grab the Url, open the connection, exchange the APDUs and the disconnect.

br,
Michael