Reading a barcode using a USB barcode scanner along with ignoring keyboard data input while scanner product id and vendor id are not known
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03-07-2019 - |
Question
Is there a way to read from a USB barcode reader while ignoring the keyboard and not knowing the PID or VID of the USB scanner? I know that there is a way of differentiating between USB scanner input and keyboard input by using the VID and or PID of the USB scanner; this was done using code from http://nicholas.piasecki.name/blog/2009/02/distinguishing-barcode-scanners-from-the-keyboard-in-winforms/ But is there another solution to differentiate between keyboard and USB scanner without putting the scanner's VID or PID in a configuration file (or source code)? The reason for not wanting to put various VIDs or PIDs in a configuration file is that, the application being developed will be deployed on numerous laptops and have arbitrary types of scanners attached to them.
Also, I don't want to configure the scanner's with a starting and or ending sequence that would be outputted, since the scanner is being used by other software on the same machine as well and I don't want to have to change the code on the other software. I don't want to program the barcode reader to be in serial mode either for the same reason mentioned previously.
Solution
There is a way to differentiate between keyboard and USB barcode reader
You can depend on these facts:
- the code scanned by barcode reader in minmum 4 characters
- the code scanned by barcode reader ends with RETURN "ENTER"
- it take less than 50 mseconds to scan the hole barcode
This is a simple form using VS2005 VB contains:
- textbox1
- textbox2
- textbox3
- Button1
- Timer1 "the time interval set to 50"ms"
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
OTHER TIPS
Well, I am using a solution pretty like the one from Ehab - I just cleaned up the code a little bit for my application. I am using a custom class for my edit controls (it is doing some other things too) - but these are the important parts for this:#
public class ScannerTextBox : TextBox
{
public bool BarcodeOnly { get; set; }
Timer timer;
private void InitializeComponent()
{
this.SuspendLayout();
this.ResumeLayout(false);
}
void timer_Tick(object sender, EventArgs e)
{
if (BarcodeOnly == true)
{
Text = "";
}
timer.Enabled = false;
}
protected override void OnKeyPress(KeyPressEventArgs e)
{
base.OnKeyPress(e);
if (BarcodeOnly == true)
{
if (timer == null)
{
timer = new Timer();
timer.Interval = 200;
timer.Tick += new EventHandler(timer_Tick);
timer.Enabled = false;
}
timer.Enabled = true;
}
if (e.KeyChar == '\r')
{
if (BarcodeOnly == true && timer != null)
{
timer.Enabled = false;
}
}
}
}
There is a another question about barcodes here, the link will send you to an answer that uses the barcode via a serial port. Maybe that's a solution for you?
IMHO: The most easy solution will be accepting the input from the keyboard.
Perhaps this is an oversimplified solution, but could you capture the key presss event and simply prevent entry via keyboard?