因此，我的任务是编写与智能卡一起工作的代码。环境是C#.Net，Xamarin。智能卡读卡器（接触式，而不是NFC）连接到霍尼韦尔手持设备。因此，由于各种原因，我不能只使用一些第三方库，我的任务是它。

Using Android.Hardware.Usb, I can get to the following.

UsbManager - created to context of application.
Scan connected USB devices to the handheld
Properly detecting the specific device.
Getting the configuration object.
Then to the interface
and finally finding the 3 endpoints.. Isochronous, Inbound and Outbound.
Request permission to use the specific device.
and finally Open the device for a UsbConnection handle.

因此，现在通信的大门已经打开，我显然需要发送一个请求出站，并从相应的出站和入站端点获得应答。
我可以构建一个APDU命令的BulkTransfer，并获得一个2字节的响应，然后我尝试在入站端口上使用APDU响应执行另一个BulkTransfer，但总是失败，返回-1。
我看过其他讨论设置通信协议，波特率等的帖子，但不确定这是否是问题所在。我对串行/USB通信的这种粒度级别完全是新的。不确定下一步要让设备进行来回通信。
这里是我正在做的连接到设备的简短总结。至于具体设备，它是一个霍尼韦尔CN 80手持式扫描仪设备，附带CAC阅读器（也是霍尼韦尔）。至于我想做的，只是想打电话验证卡是否存在（或者不是）。我并不是想实际向设备发送数据，只是一个命令来查询设备并得到适当的回复。

public void attemptingSmartCommunications()
{
   _myUsbManager = (UsbManager)_myMainActivity.GetSystemService(Context.UsbService);
   foreach (var d in _myUsbManager.DeviceList)
   {  // method checks the device for proper VID/PID
      var dev = d.Value;
      if (isExpectedDevice(dev))
      {
         for (var dc = 0; dc < dev.ConfigurationCount; dc++)
         {
            // SHOULD only be 1 configuration from what I have encountered.
            _myUsbConfiguration = dev.GetConfiguration(dc);

            for (var di = 0; di < _myUsbConfiguration.InterfaceCount; di++)
            {
               _myUsbInterface = _myUsbConfiguration.GetInterface(di);
               // Add on context of each endpoint
               for (var ep = 0; ep < _myUsbInterface.EndpointCount; ep++)
               {
                  var intEndpoint = _myUsbInterface.GetEndpoint(ep);

                  // which one do we need, store into their own respecive properties
                  // for in/out/isochronous
                  switch (intEndpoint.Address.ToString())
                  {
                     case "XferIsochronous":
                        // Control pipe for communication
                        _myIsochronousEndpoint = intEndpoint;
                        break;

                     case "130":
                        // Read IN FROM the USB Device with response
                        _myInEndpoint = intEndpoint;
                        break;

                     case "131":
                        // Write OUT TO the USB Device with command/request
                        _myOutEndpoint = intEndpoint;
                        break;

                  }
               }

               // now, I have the endpoints to request send and read back, make sure permission
               if( _myUsbManager.HasPermission(_myUsbDevice))
               {
                  myConnection = _myUsbManager.OpenDevice(_myUsbDevice);
                  var apdu = MyStaticSmartCardAPDUCommand;
                  // prepares the 4-byte request of CLA, INS, P1, P2 (no data in request)
                  var byteBuffer = apdu.CommandAsBytes(); 
                  var bufferLen = byteBuffer.Length;
                  var resultBytes = _myUsbDeviceConnection.BulkTransfer(_myOutEndpoint, byteBuffer, bufferLen, 2000);
                  // I get indication of 2 byte response
                  if( resultBytes > 0 )
                  {
                     // default buffer prepared with 4 bytes.  SW1, SW2 + 2 expected bytes
                     var apduResp = new APDUResponse(resultBytes);
                     byteBuffer = apduResp.GetResponseBuffer();
                     var responseStatus = _myUsbDeviceConnection.BulkTransfer(_myInEndpoint, byteBuffer, byteBuffer.Length, 3000);

                     // HERE is where it always fails.  
                     // Am I on the right track?  Completely out of it?
                  }
               }
            }
         }
      }
   }
}