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HP Forum Archive 14

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HP 41 Bar Code Language
Message #1 Posted by Cristiano on 3 May 2004, 6:07 p.m.

I have been looking to write some bar code for the HP-41 optical wand. I am trying to understand the format used. I snooped around the web and found some Windows software to write it; however no clear explanation on how to associate instructions or alphanumeric input to the bars. My goal is also to be able to read information barcoded in other languages (e.g. UPC-A etc). Any input or link on where to look? Thanks CC

      
Re: HP 41 Bar Code Language
Message #2 Posted by Eric Smith on 3 May 2004, 6:59 p.m.,
in response to message #1 by Cristiano

You want the manual "Creating your own HP-41 Barcode", which is available on the museum CD-ROM set.

The manual on the 82153A bar code wand describes functions that can be used to read "foreign" barcode formats. There are some limitations; I'm not sure whether UPC-A can be read.

      
Re: HP 41 Bar Code Language
Message #3 Posted by Miki Mihajlovic on 3 May 2004, 6:59 p.m.,
in response to message #1 by Cristiano

I am not sure about the other bar code languages but HP-41 is rather simple. Bars simply mean 0 or 1 bit. 0-bit is a thin bar while 1-bit is a thick bar. White space is of same thickness as 0-bit. Absolute thickness is not important (although there might be some limits) since the wand reads only pulses and their duration. Beginning (two thin lines)and the end (hick-thin) of the bar code sequence (line) is marked so the wand knows if it reads left-to-right or right-to-left. I think that I have seen a detailed description in one of the PPC journals but I am not positive about it.

1234

      
Re: HP 41 Bar Code Language
Message #4 Posted by Tony Duell on 4 May 2004, 2:39 p.m.,
in response to message #1 by Cristiano

My 'LIF Utilities for Linux', available from the HPCC web site (http://www.hpcc.org) include programs to generate HP41 program and data barcode. You'll need the 'Creating your own HP41 Barcode' book in order to understand them, but these programs may clarify a few points (they're commented C source, should be fairly portable).

      
Re: HP 41 Bar Code Language
Message #5 Posted by Ray on 5 May 2004, 1:39 a.m.,
in response to message #1 by Cristiano

The barcode also uses two bars of data on each side to indicate whether data is being read left to right, or right to left. I think it works like this in a string of data:

00DDDDDDDDDDDDDDDDDDDDDDDDD10

Where: D=data string itself (could be anything) 0=thin bar 1=thick bar

This shows how the ends of the data are organized, so the reader knows whether it is reading right to left or left to right.

Someone correct me if I'm wrong. Hope this helps.


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