USB finger print scanner

[tetra]

Hi everyone, I'm in my 3rd and final year of school as a Computer Engineering student and have one last programming intense task left. A colleague and I are developing a Visual Basic application that will take input from a biometrics finger print scanner. This device will be USB.

I was wondering how to interface these devices for communication? I will have the driver from the manufacturer, but as far as coding it goes I am not too sure.

Can anybody give me a nudge in the right direction?

Thanks in advance!

 

[jmcilhinney]

The driver will provide an API. You would need the driver documentation so you know what that is. You would then most likely be using Platform Invoke to interact with the driver, like you do to invoke the Windows API. If you don't know how to do that then repost and we can provide more info.

 

[tetra]

Thanks for responding promptly. I'm not too sure what you mean by this API, and the Platform Invoke.

Could you provide some more info?
Thanks!

 

[jmcilhinney]

Drivers are generally written in unmanaged C/C++. Those languages allow you to export functions, which means that they can be called from outside the DLL. In VB code you can import those functions by declaring them appropriately in your own code and then calling them like any other method.

You need to either declare them with the Declare key word or else by applying the DllImport attribute. The Declare key word is a hold-over from VB6, while the DllImport attribute is the standard .NET way to declare external functions, i.e. DllImport is used in all .NET languages. The MSDN documentation for either can show you how they are used.

In order to know what and how to declare these functions you need to have the documentation for the driver's API. API stands for Application/Programming Interface. It basically means the programming interface that any system exposes to external programs. You need to know what functions your driver exports and what they do so that you know how to declare and call them in your own code.

I would advise creating a component as an interface between the driver and the rest of your code, which is good OOP style.

 

[tetra]

I see, in the case of the USB Barcode scanner, the input is simply read like it was from a keyboard and can be put in a textbox correct? I'm going to associate the print with a string somehow so the VB app knows what it's dealing with since it cannot decode information from a print picture.

Is this concept possible in your view?

 

[jmcilhinney]

In the case of a barcode scanner that attaches via a keyboard wedge there's no need to do anything. The whole point is that the data read from the scanner appears to the system as though it came from a keyboard. How do you usually collect keyboard input?

 

[tetra]

Thanks for the info jmcilhinney. Would you happen to know if most USB biometrics scanners have support for SDK compatibility?

 

[jmcilhinney]

Never used one but drivers are pointless if you can't interact with them. The standard of the documentation is likely to vary.