Send multiple transceive command

[masty73]

Hello all,

I'm trying to send multiple transceive commands to a NTAG213. (Android)
I need to send the PWD_AUTH command and then the read command (in the same session).
I'm using the demo app as test ( method startWriterSession in tranceive.page.ts )

Do you have a snippet of code that can help me ?

I tryed something like this:

this.nfcService.scannedTag$
      .pipe(takeUntil(this.cancel$), take(1), untilDestroyed(this))
      .subscribe(async () => {
      
        const data = this.hexToBytesPipe.transform('1B:A1:A2:A3:A4','',':',);
        console.info ("*** Send data: " + data);
        this.transceiveResponse = await this.nfcService.transceive(
          this.selectedTechType,
          data,
        );
        console.info ("*** PACK: " + this.transceiveResponse) ;

        const data2 = this.hexToBytesPipe.transform('30:10','',':',);
        console.info ("*** Send data2: " + data2);
        this.transceiveResponse = await this.nfcService.transceive(
          this.selectedTechType,
          data2,
        );
        console.info ("*** RESP: " + this.transceiveResponse) ;

        this.changeDetectorRef.detectChanges();
        this.activeWriterAlert?.dismiss();
        await this.nfcService.stopScanSession();
      });

I got an error when I send the second data (data2):

File: http://192.168.20.45:8100/src_app_modules_transceive_transceive_module_ts.js - Line 178 - Msg: *** PACK: 0,0
File: http://192.168.20.45:8100/src_app_modules_transceive_transceive_module_ts.js - Line 182 - Msg: *** Send data2: 48,16
To native (Capacitor plugin): callbackId: 114069243, pluginId: Nfc, methodName: isSupported
callback: 114069243, pluginId: Nfc, methodName: isSupported, methodData: {}
To native (Capacitor plugin): callbackId: 114069244, pluginId: Nfc, methodName: isEnabled
callback: 114069244, pluginId: Nfc, methodName: isEnabled, methodData: {}
To native (Capacitor plugin): callbackId: 114069245, pluginId: Nfc, methodName: transceive
callback: 114069245, pluginId: Nfc, methodName: transceive, methodData: {"techType":"NFC_A","data":[48,16]}
An unknown error has occurred.

Anyone has sent two commands in the same session?

[robingenz]

Thank you for your request. I will take a look in the next days.

[masty73]

After some investigating I've seen that (for Android) in the Nfc.java file, the transceive method:

1. call "tagTechnology.connect();"
2. send and get the Transceive data
3. call "tagTechnology.close();"

If you try to send multiple transceive message wich needs same session (like password + read message) the "tagTechnologi.close()" command closes the session, so can't work correctly.

I tryed to send password Authentication and read command between tagTechnology.connect() and tagTechnology.close() and it works correctly.

So in the Nfc.java for reading the #x10 page NfcA NTAG213 card which is password protected (assuming password is 'A1 A2 A3 A4') you should use:

1. call "tagTechnology.connect();"
2. send data: "1B A1 A2 A3 A4' (PWS_AUTH command)
3. receive PACK (00 00 if not changed the default)
4. send data: "30 10" (READ page #x10)
5. receive page #x10 content bytes
6. call "tagTechnology.close();"

Maybe this can be useful for someone

[robingenz]

Thanks for sharing! We should add an option to manually connect and disconnect from a tag. I created a feature request for this: #39