Sunday, December 18, 2011

Bar-code readers

There is huge zoo of these devices. They are divided to different groups from marketing and user point of view. In this post I'd like to introduce you a third point of view. Point of view of software engineer.

1. Quick start

Bar-code reader is always read only device for PC.
Bar-code reader could be configured via scanning special bar-codes from it's user manual
You can configure many parameters in that way. The most interesting for us are prefix and suffix of code sequence (I'll back to this later in details)

2. Two kinds of bar-code readers

I divided our bar-code readers zoo in two parts: 1. Bar-code readers that interact with PC like HID devices (these includes PS/2 and USB bar-code readers); 2. Bar-code readers that connects via RS-232 port.
Both of these kinds of devices have their advantages and disadvantages.

2.1. HID devices

+ Easy to prepare your program to work with them.
+ You have no need to handle reconnection issues and the like.
- There is sometimes hard to determine if we have input from bar-code reader or from keyboard (but this can be solved by using a prefixes and suffixes).

2.2. RS- 232 devices

+ You always know that input that you receive is from bar-code reader.
- You should handle reading from RS-232 port in your program.
- You should handle connection issues in your program.


If you make some mistakes in configuration of bar-code readers, there is a page with “reset to factory defaults” sequence in user manual (Check if you have this page before making any changes in configuration).