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This has nothing to do with Visual Basic. You are asking for information on how your device works. That information should be in the manufacturer's documents.
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We're talking for general usb barcode readers that act like a keyboard.
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Then the same applies as for any keyboard.
Bastard Programmer from Hell 
If you can't read my code, try converting it here[^]
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Yes, and the behaviour of the barcode reader is specific to its design & manufacture. So you still need to read the manual to see how it presents itself and its data.
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What about programs that can work with any kind of usb barcode readers ? so they are general and what they need is only to plug the barcode reader.
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Yes, and what happens then?
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The barcode reader is working as expected.
I've seen some programs ( of course I don't have the code ) that can use any type of USB barcode readers ( without any special configuration ) and can distinguish between 2 modes ( for example focusing a textbox when I type with keyboard nothing is displayed , when I read with barcode reader the barcode is displayed ). And also if I focus a listbox or another control in the form, and read with barcode reader , the barcode is read and displayed in the right textbox without focusing it.And I've tested these programs even with cheap no name Chinese barcode readers and always work perfectly.
So it seems a way should exist.
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desanti wrote: So it seems a way should exist.
Simple; learn C++ and write a generic device driver.
..but in VB.NET, you are limited to what the software that is installed for the device allows you to do.
Bastard Programmer from Hell 
If you can't read my code, try converting it here[^]
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These are USB barcode readers that are configured to act like keyboards. No software are needed to install for these devices. Windows has that "Generic drivers" built in.So I can plug different kinds of these barcode readers , at the same Pc and they use the same driver built in on windows.
So these barcode readers are like keyboards with only 1 difference : They can "type" much more chars at a small time compared with typing on keyboard.
I hope that someone can help me working on this idea.
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Yes, Windows already has multiple generic device-drivers. The functionality provided is exactly that, it fits most needs.
If you need more, you contact the manufacturer and see if they have an SDK;
..but from VB? Good luck there 
Bastard Programmer from Hell
If you can't read my code, try converting it here[^]
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Then those programs must be communicating direct to the device(s) via the USB interface. Alternatively, as Dave K already suggested, the device sends extra data to identify itself. Google (as usual) is the place to start your research.
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I've tested and it seems that these barcode readers only send a list of chars and an "ENTER" at the end. So no special characters.
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No , because even on normal keyboard I can write and press ENTER at the end. How to distinguish that was from keyboard or from Barcode reader ?
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There are multiple types of barcode readers. What you're talking about is a "keyboard wedge" type that, as you already know, act like a keyboard.
But, usually they are programmable to prepend and/or append character data to the barcode it reads. This allows applications to add an "attention sequence" to the data it's "keying" into your application. Typically, your application looks for this data coming from the keyboard and can use that data to know that the next characters are part of the barcode until it sees the appended sequence.
This makes it possible to use the data WITHOUT having to know which "keyboard" the data came from. THIS IS WHY YOU READ THE DOCUMENTATION ON THE DEVICE YOU'RE USING!
There are also other interface types, such as Ethernet-based devices, that you can code against. But, again, this is where you read the documentation on your device.
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Option 1 is a HUGE pain in the ass to implement and isn't reliable.
Option 2 is how this is normally done in a Windows Forms app.
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I've seen some programs ( of course I don't have the code ) that can use any type of USB barcode readers ( without any special configuration ) and can distinguish between 2 modes ( for example focusing a textbox when I type with keyboard nothing is displayed , when I read with barcode reader the barcode is displayed ). And also if I focus a listbox or another control in the form, and read with barcode reader , the barcode is read and displayed in the right textbox without focusing it.And I've tested these programs even with cheap no name Chinese barcode readers and always work perfectly.
So it seems a way should exist.
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I already told you how it works. Option #2.
How do I know? I've done it that way.
Digging through the whole "figure out which USB device the key came from" thing is a bit excessive.
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ok , but option 2 handle all messages at form level , but the messages can be from barcode readers or from keyboard.
How to distinguish ?
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I already told you how. Prefix and Postfix sequences attached to the barcode.
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Sorry , but these barcode readers cannot be configured to have a special character. Have no software that can use to configure these.
They only produce a list of chars and an "enter" at the end.
The only difference is that the barcode can produce much more chars at a small time compared with typing on keyboard. For that I hope to get some help to work on this idea because it seems is the only difference that these barcode have compared with a keyboard.
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Thank you !
I've already read the article for RAW Input.
I've tested and can detect from which device the input came from.
But the problem remain because he detect both keyboard and Barcode reader as Keyboard1 and keyboad2. The problem is that how can I define in my application ? Because both keyboard and Barcode reader are USB , and when I will distribute my application , on one computer the barcode reader may be Keyboard 1 , on another may be Keyboard 2..? So this is a problem.
Do you have any suggestion ?
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yeah, do a bunch of research. I can't do it for you. I simply don't have the time.
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