Barcode Scanner Interfaces – Keepin’ it Easy with a Keyboard Wedge

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Welcome to Part 2 of my Barcode Scanner Interface blog series, in which I outline the three primary methods of physically connecting a barcode scanner to a computer: Serial, Keyboard Wedge, and USB.  If you missed Part 1 on using a serial interface, you can read it here.

The keyboard wedge interface gets its name from the way it wedges itself between the keyboard and the computer. A keyboard wedge cable has three connectors: one for the barcode scanner, one for the computer, and one for the keyboard. Keyboard wedge cables designed for use with laptop computers only have two connectors: one for the barcode scanner and a PS/2 connector for the computer.

PS-2 Connector

PS-2 Connector for the Computer

The operating system (OS) cannot distinguish between data that comes from the keyboard and data that comes from the barcode scanner. Because of this, an application does not require specific functionality to support a barcode scanner connected with a keyboard wedge cable. If the application allows input from the keyboard, it will accept input from such a barcode scanner. In fact, the application cannot differentiate between data from the keyboard and the scanner.

Most barcode scanners connected with a keyboard wedge cable get their power from the computer’s keyboard port. Some keyboard wedge cables allows for an optional external power supply. This can serve to either power the scanner or, for cordless barcode scanners, to charge the battery. You should check the documentation for your device to determine if it requires an external power supply. A few barcode scanners with keyboard wedge interfaces will not work without a physical connection to a keyboard.

Because most barcode scanners support other interfaces besides keyboard wedge, you must ensure that you’ve configured the scanner prior to using this connection.

A keyboard wedge interface is the easiest of the standard barcode interfaces to configure. I recommend using it in the following instances:

  1. Your hardware only supports a keyboard interface.
  2. Your application does not support a COM port (serial) interface.
  3. You have multiple applications running at once and require the barcode data to go to whichever application is in the foreground.

That sums up a keyboard wedge interface pretty nicely, but feel free to contact me if you have any questions. Be sure to stop back soon and read my last blog in this series on a USB interface.