Practical Arduino Cool Projects for Open Source Hardware- P11: A schematic or circuit diagram is a diagram that describes the interconnections in an electrical or electronic device. In the projects presented in Practical Arduino, we’ve taken the approach of providing both a photograph and/or line drawing of the completed device along with a schematic. While learning to read schematics takes a modest investment of your time, it will prove useful time and time again as you develop your projects. With that in mind, we present a quick how-to in this section | CHAPTER 5 PS 2 KEYBOARD OR MOUSE INPUT Variations Barcode Reader for a Stock Control System A number of seemingly exotic peripherals such as barcode scanners as shown in Figure 5-11 actually present themselves as keyboards to a host computer. That s very handy because it means you don t need any special drivers or hardware to talk to them. A typical barcode scanner reads the code and then immediately sends it to the host as a series of keypresses so as far as the computer is concerned scanning a barcode is exactly the same as if you simply typed in the barcode string on a keyboard. Most barcode scanners have a number of options that can be set such as whether they should automatically append a carriage return at the end of each scan. This means you should be able to connect any PS 2 barcode scanner to your Arduino using the shield and sketch shown in this project and have any barcode you scan sent through to the Arduino as a series of characters followed by a carriage return. Very neat. By adding an Ethernet shield to your Arduino and creating a simple web client in your sketch you can have it call a web service and submit the barcode value whenever you scan a barcode. The web service could be anything from a home inventory management system scan groceries when you bring them home from the shops to add them to a stock list or scan wrappers as you thrown items out so they can be added to a shopping list to a CD collection manager or stock-take system. Or if you add a battery pack and use an XBee module or WiShield instead of a regular Ethernet shield you can create a networkenabled fully wireless intelligent barcode scanner Figure 5-11. PS 2 barcode scanner 79 CHAPTER 5 PS 2 KEYBOARD OR MOUSE INPUT Resources For more detailed information about how the PS 2 protocol works as well as the electrical and mechanical standards there are some very good guides on both and Wikipedia ps2keyboard .
