Another 41c BarCode Question



#7

Can somebody let me know (post here or email me) the physical specifications for HP41 barcode? I don't have the book, and would really like to know: 1) Optimum Ratio of widths (space, thin bar, thick bar) 2) Optimum size for one or all of the above.

I've been adding "features" to my unified decompiler/program lister, and since printing barcode was easier than comprehensively deciphering XROM xx,yy to commands, I did it first. It works, but I just don't know the right sizes to put out!

Thanks Dan danm@hevanet.com Portland, Oregon USA


#8

If my memory helps, there are only two widths: the narrower bar is half the width of the other. There is no "right size" since the Wand sensor just delivers a series of pulses based on the transitions from dark to white and white to dark. As far as the movement is smooth enough, the timing of the pulses let the Wand estimate the width of each simbol as it is scanned. It merely sorts the time intervals in two classes: those with duration similar to X and those with durations similar to 2x. A recomendation of adequate sizes may arise from an estimation of reasonable speeds for the hand movement.


#9

Thanks for the response. I was concerned with my barcode printing that the bars were too close together, and I kept on getting "checksum err" until I printed it out really huge to spread the bars out a little bit. The thin bar in some old generated barcode appears to be about 1/3x the width of the thicker bar.

The reason I thought the space is important is to keep the bars apart... not wanting 2 bars inside the little window of the wand at the same time. Perhaps this is not too big a deal, and if I widen my narrow bars out to 1/2 of the thick ones, keep the space about the diameter of the wand's "eye" then I'll be OK.

Thanks again. Someday I'll have this all debugged and ready for public distribution. If you want a "beta" version (or a "better beta," for those of you that have it already) please email.


#10

as you print the bars narrower and narrower, you have to start worying about the fact that the ink may spread (on some printers more than others). You can compensate for this by making the bars slightly narrower.

The barcode manual lists minimum widths (from memory) which is dependant on the beam width.


#11

The minimum width about 4/75" (four of the 75 dpi dots from an HP laserjet) for the narrow bar and twice that for the thick bar (zero's and one's). The white space is the same width as the narrow bar.


#12

My problem is "resolved." I'm using barcode with the ratio of 1:1:2 for thinbar:space:thickbar and it seems to work fine. I've sized it so a typical/long line of barcode will fit on an 8.5x11 inch page. I think the actual width of the thin bar at this scale is less than 1/20". Still working out some bugs from the printing program (which works!) and will get it to the web site someday. Oh yeah, to use this you need to have the program file (in binary) accessible on a PC drive.


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