C# – Read data from USB barcode scanner in .NET received event

There is a way to differentiate between keyboard and USB barcode reader

Starting with the following assumptions:

1. the code scanned by barcode reader will be at least 4 characters long
2. the code scanned by barcode reader ends with an "ENTER" keypress
3. it take less than 50 ms to transmit the entire barcode

This simple form using VS2005 VB contains:

1. TextBox1
2. TextBox2
3. TextBox3
4. Button1
5. Timer1 "the time interval set to 50ms"

Public Class Form1

Dim BarcodeStr As String = ""
Dim IsBarcodeTaken As Boolean = False
Dim Str As String = ""
Dim str3 As String = ""


Private Sub Form1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown

    If Timer1.Enabled = False Then
        Str = TextBox1.Text
        str3 = TextBox3.Text
    End If

End Sub

Private Sub Form1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles Me.KeyPress
    If Timer1.Enabled = False Then
        Timer1.Enabled = True
    End If


    BarcodeStr = BarcodeStr & e.KeyChar
    If Asc(e.KeyChar) = 13 And Len(BarcodeStr) >= 4 Then
        IsBarcodeTaken = True
        TextBox2.Text = BarcodeStr


    End If

End Sub
Private Sub Form1_KeyUp(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyUp
    If IsBarcodeTaken = True Then
        TextBox1.Text = Str
        TextBox1.Select(Len(TextBox1.Text), 0)
        Str = ""

        TextBox3.Text = str3
        TextBox3.Select(Len(TextBox3.Text), 0)
        str3 = ""
    End If

End Sub


Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
    BarcodeStr = ""
    IsBarcodeTaken = False
    Timer1.Enabled = False
End Sub


Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    TextBox2.Text = ""

End Sub

End Class

If it is a USB reader, you should find the .net drivers that come with it, such that you get a class which provides the IO and perhaps more functionality.

If the scanner has internally a USB to Serial converter, then you should see in your Device Manager which COM port is in use by the scanner. In that case, you can use the SerialPort class for communication to the device. Note that you should set the settings (i.e. baudrate, parity bit, stop bit, etc) correct before you can have any communication.