Question

I have an extremely simple application running off a series of deprecated scanners that picks up a barcode scan off a serial port and sends back to the scanner an ok that it received the scan. Based on that, the scanner flashes green and the user knows they can continue.

I like this model over my understanding of a keyboard wedge because if something happens to the application picking up the scan (the application hangs, the form with the focus gets changed, the PC hangs, the PC can t keep up picking up the scans), the person holding the scan gun will know there is a problem because they won t receive the green flash and they won t be able to continue scanning.

I m looking at adding some scanners and it seems many people are using barcode scanners that effectively act as keyboard wedges. Some of these scanners have ranges that exceed 100 feet, implying people are using them far away from the PC (as my users are). So I m wondering if I m missing something regarding the keyboard wedge model. Is there some mechanism I m missing to ensure that a scan decoded by a scanner acting as a keyboard wedge actually reaches the application running on the PC? A full-blown hand-held computer running something like Windows Mobile seems like massive overkill for just wanting to ensure my user is not scanning data that isn t going into the application and so does even a mid-range scanner with a keypad and screen, but is the latter the entry point for any sort of programmatibility of the scanner?

Answer 1

You are correct- there isn t a feedback loop to the scanner when running as a wedge. We use wedge scanners a lot, and in a modern environment (ie, Windows, multiple apps, etc), focus, "dropped scans", etc, are all real problems.

We re in the middle of switching over to a different way. If you have your choice of hardware, many new USB barcode scanners have the ability to operate in a serial emulation mode that allows the same kind of interaction you describe (where you can prevent a second scan until the host has ACK d the first, or you can beep/flash something on the scanner as an ACK). Also, there s a USB HID POS (point of sale) mode that some higher-end USB scanners support that gives you an even greater degree of flexibility, with the added bonus of "driver free" installation (it looks like a generic HID device to the system, like a joystick or keyboard, but with 2-way comm ability). The downside of POS mode is that it s a little harder than serial programming, but there are abstraction layers available for different platforms.

Answer 2

RF mobile computers with built in scanners, like the Symbol MC9090-G, are by far the most flexible and what we use the most. As for wedges, depending on the distance from the PC and factory environment - we have used visual feedback via the PC screen and audio via the PC speakers. The users listen for the audio feedback after each scan and when they don t hear it they look back to the PC screen for visual feedback as to the problem. Not perfect but it has worked well.

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