Revision as of 12:05, 20 February 2012

This article provides a workaround to avoid application crashes when closing the connection to an NFC Tag Type 4 on Symbian Belle.

Introduction

When an NFC tag is lost/separated from the device a handler should be called to close the connection. Due to a bug in the NFC implementation on Symbian Belle, we need to first deactivate the connection before closing it, or the application will panic.

The bug is fixed in the mainline and should appear in firmware in future released.

How to produce the bug

1. Implement your code to handle the tag lost event as below. Note that this is the correct way to handle the event:

   void CNfcHandler::TagLost() 
   { 
     iTag->CloseConnection(*iIso14443Connection); 
     delete iIso14443Connection; 
     iIso14443Connection = 0; 
   }

2. Run the application
3. Touch an NFC tag type 4 to the device (for example, a Nokia C7) and then remove it

The NFC app is closed due to a panic (Symbian unexpected exception).

Workaround

The following code can be used to workaround this crash on Symbian Belle:

void CNfcHandler::TagLost() 
{ 
  if(iIso14443Connection->IsActivated()) { 
    iIso14443Connection->Deactivate(); 
  } 
  iTag->CloseConnection(*iIso14443Connection); 
  delete iIso14443Connection; 
  iIso14443Connection = 0; 
}

Device SW used to test

Use C7 with FW 022.013 and FW022.014