.NET (Core and Framework)

29-May-06 14:44

Hi all,
i am trying to communicate with a virtual com port to get the input from a scanner(a USB device) using the system.io.ports class. i have opened the port (port.open), but when i try to scan some input, the program (using vb.net) won't trigger the DataReceived events, any idea how to get the input from the scanner? Thanks in advance!

elcheah

Office Lineman30-May-06 7:18

30-May-06 7:18

USB devices do not work that way. For a scanner, you should be using TWAIN or some other appropriate interface.

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I've killed again, haven't I?

elcheah30-May-06 23:13

30-May-06 23:13

Thanks for your reply,
i have stucked there for a very ong time Unsure | :~

,i have searched for TWAIN like you have suggested to me, but i am still lost, how to use TWAIN in vb.net? can you give me some guidelines or any tutorial site i can refer to? Thanks

Office Lineman31-May-06 5:42

31-May-06 5:42

There are articles about using TWAIN. Here's one now.[^]

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I've killed again, haven't I?

elcheah31-May-06 17:08

31-May-06 17:08

Thanks for that article,
Is TWAIN for just image scanning? what about a bar code USB scanner? is that the same?

Office Lineman31-May-06 19:52

31-May-06 19:52

Yes, TWAIN is for image acquisition from imaging devices like scanners and digital cameras.

A bar code scanner, on the other hand, is not an imaging device. They could require one of many interfaces. Most USB bar code scanners emulate keyboard input. A simple way to test this, if the bar code scanner is set up, is to open Notepad, focus in the text area, and scan a bar code--like off a box of food or a book.

If, by "scanner" earlier, you meant a bar code scanner, and it supports a virtual COM port, then you can, in fact, use the SerialPort class to connect to that virtual COM port and translate that data as needed. I used SoftCom32 when I first started with a serial (RS232) bar code scanner; it's a tray app that does exactly that--monitors the COM port for data, then emulates keystrokes. I've since replaced it with a sloppy little number I wrote in C# to interface directly to my app, so I don't get stray scans.

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I've killed again, haven't I?

elcheah31-May-06 21:50

31-May-06 21:50

I have tried to use the SerialPort class to connect the barcode scanner's virtual COM port, i can detect the scanner's COM port but i failed to read the input in my program. When i try to scan the DataReceived event is not triggered Frown | :(

but i can read the input into the HyperTerminal in windows, Any idea how to do read the input of the barcode scanner in vb.net using that class? or is there any alternatives besides that? Thanks

Office Lineman1-Jun-06 7:06

1-Jun-06 7:06

I don't see any reason why VB wouldn't let you scan bar codes if C# will.

You can post your port opening code so we can take a look at it.

There are a couple simple things to check:

Make sure your ReceivedBytesThreshold isn't set to some ungodly high number (should default to 1)
Make sure you call Open() after you create the port

If it will help, I can post my C# class code this evening when I get back to that computer, so you can see the way I did it. I took a threaded byte-at-a-time approach because the DataReceived events I got resulted in fragmented scans (e.g. scanning "1234567890" got broken up into two events, "123456" and "7890") and I was scanning variable-length bar codes, so I couldn't just set it to fire DataReceived after n bytes.

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I've killed again, haven't I?

elcheah1-Jun-06 16:35

1-Jun-06 16:35

This is how I open a com port

<br />
       With serialPort<br />
          .ReceivedBytesThreshold = 1<br />
          .PortName = "COM3"<br />
          .BaudRate = 9600<br />
          .Parity = IO.Ports.Parity.None<br />
          .DataBits = 8<br />
          .StopBits = IO.Ports.StopBits.One<br />
       End With<br />
       serialPort.Open()<br />

and detect my com port using

For i As Integer = 0 To My.Computer.Ports.SerialPortNames.Count - 1<br />
         combobox.Items.Add(My.Computer.Ports.SerialPortNames(i))  <br />
      Next

after i open the COM port, i try to scan in some input won't trigger DataReceived events, anything that i have done wrongly? or anything i should set? Confused | :confused:

elcheah1-Jun-06 20:20

1-Jun-06 20:20

for my data received events goes this way

<br />
Private Sub serialPort_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles serialPort.DataReceived<br />
        Me.Invoke(New EventHandler(AddressOf DoUpdate))<br />
End Sub<br />
<br />
Private Sub DoUpdate(ByVal s As Object, ByVal e As EventArgs)<br />
    txtDataReceived.Text = txtDataReceived.Text + serialPort.ReadExisting()<br />
End Sub<br />

anything i have done wrongly? please advice... Thanks

elcheah2-Jun-06 0:10

2-Jun-06 0:10

Hey, i got it worked, i just set the RtsEnable to true then it worked
serialPort.RtsEnable = True

Thanks for all your support Smile | :)

Office Lineman2-Jun-06 6:24