Error : Object reference not set to instance of the object

• What i am missing in this code

  i refer this link for printing 

  http://www.neodynamic.com/demo-faq/thermal-label-sdk-net/how-to-print-barcode-thermal-labels-in-ASP-NET-by-using

protected void Button1_Click(object sender, EventArgs e)
        {
         
                Neodynamic.SDK.Printing.ThermalLabel tLabel = new Neodynamic.SDK.Printing.ThermalLabel(Neodynamic.SDK.Printing.UnitType.Cm, 6, 0);

               
                Neodynamic.SDK.Printing.BarcodeItem bcItem = new Neodynamic.SDK.Printing.BarcodeItem();
             
                bcItem.Symbology = Neodynamic.SDK.Printing.BarcodeSymbology.Code128;
   
        
                bcItem.Code = Request["TextBox1.Text"];
               
                bcItem.X = 0.5;
                bcItem.Y = 0.5;
           
                bcItem.BarWidth = 0.025;
                bcItem.BarHeight = 2;


               
                tLabel.Items.Add(bcItem);


            
                Neodynamic.SDK.Printing.PrintJob pj = new Neodynamic.SDK.Printing.PrintJob();
         
                pj.PrinterSettings.Communication.CommunicationType = Neodynamic.SDK.Printing.CommunicationType.USB; <<---- Error 
              
                pj.PrinterSettings.Dpi = 203;
        
                pj.PrinterSettings.ProgrammingLanguage = Neodynamic.SDK.Printing.ProgrammingLanguage.EPL;
   
                pj.PrinterSettings.PrinterName = "ZDesigner TLP 2844";
         
                pj.Copies = 1;
                pj.Print(tLabel);
            }
        }

       
    }