Barcodes

technical details

David B. VanHorn has posted an excellent tutorial on how to write your own barcode decoding software: http://dvanhorn.org/Barcode/. (He uses Atmel AVR, but the tutorial is general enough to apply to just about any processor).

UPC codes

UPC codes are perhaps the most commonly-encountered kind of bar code.

• the UPC database http://www.upcdatabase.com/
• http://www.beakman.com/upc/barcode.html
• http://www.rnrcomputing.com/upc/
• http://www.dvanhorn.org/Micros/All/Index.php UPC EAN information

Barcode scanners

• http://www.metrologic.com/vsts1095.htm Omnidirectional scanning, as defined by Roger C. Palmer, The Bar Code Book, is when a "series of straight or curved scanning lines of varying directions in the form of a starburst, a lissajous pattern, or other multiangle arrangement are projected at the symbol and one or more of them will be able to cross all of the symbol's bars and spaces, no matter what the orientation."

Barcode decoders (chip sets)

Some hardware people use to read barcodes.

• David B. VanHorn sells an amazing little 8 pin chip http://dvanhorn.org/Barcodechip/ that takes a digital hi/lo from a handheld scanner, and decodes UPC-A, UPC-E, EAN-8, EAN-13, JAN and Bookland codes in either direction.
• The HBCR-2010 and HBCR-2011 barcode decoder chip
• CueCat

  The CueCat barcode scanner (free (tanstaafl: it reports its use to them and thereby tracks your web browsing and purchasing habits) with a visit to Radio Shack) can be hacked to use as a standard barcode scanner:

  • http://s1066194.umsl.edu/cuecrap/
  • http://www.flyingbuttmonkeys.com/mirrors/www.net-noise.com/jshenry/cuecat_mods/ Quite good details also at
  • http://air-soldier.com/~cuecat/

barcode encoders

(software to run on a PC to take the data and encode it into a barcode image)

• http://www.renderbar.com/sample.php Javascript to make many types of barcodes+ (Cached 20050309)
• http://lists.linux.it/pipermail/barcode/2002-November/000136.html Perl script to produce the barcode.+
• http://www.246.dk/code39.html Barcode 3of9 from Javascript
• http://www.246.dk/code128.html Barcode 128 from Javascript
• http://www.telepen-barcode.co.uk/images/downloads/BarcodeSymbology.pdf Specs for the Telepen Barcode system.+
• http://www.barcode-1.com/
• http://www.rdrop.com/~cary/html/machine_vision.html
• http://pe.usps.gov/cpim/ftp/pubs/Pub25/Pub25.pdf
• http://www.milk.com/barcode/ online generator for UPC barcodes.

code

Code:

• #!/usr/bin/perl
  # Markus.Kuhn@cl.cam.ac.uk, 2002-11-22
  
  # Encode 7-bit ASCII string into Telepen barcode
  # http://www.telepen-barcode.co.uk/barcode_symbol.asp
  # Output: string in which '.' and 'B' represent equally wide white and
  #         black vertical strokes.
  sub telepen
  {
      my ($text) = @_;
      my $bits;
      my $barcode;
      my $checksum = 0;
  
      # Append checksum byte to $text
      for ($i = 0; $i < length($text); $i++) {
  	$checksum += ord(substr($text, $i, 1)) & 0x7f;
      }
      $text .= chr(~($checksum % 127) & 0x7f);
      # Convert $text to LSB-first bit sequence with even parity
      while (length($text) > 0) {
  	my $char = ord($text);
  	my $ones = 0;
  	$text = substr($text, 1);
  	$checksum += $char;
  	for ($i = 0; $i < 7; $i++) {
  	    $ones +=  ($char >> $i) & 1;
  	    $bits .= (($char >> $i) & 1) ? '1' : '0';
  	}
  	$bits .= ($ones & 1) ? '1' : '0';
      };
      # Add start and stop codes
      $bits = "11111010${bits}01011111";
      # Now apply Telepen encoding state machine
      my $state = 0;
      while (length($bits) > 0) {
  	if ($bits =~ /^010/ && $state == 0) {
  	    $barcode .= 'BBB...';
  	    $bits = $';
  	} elsif ($bits =~ /^00/ && $state == 0) {
  	    $barcode .= 'BBB.';
  	    $bits = $';
  	} elsif ($bits =~ /^01/ && $state == 0) {
  	    $barcode .= 'B...';
  	    $bits = $';
  	    $state = 1;
  	} elsif ($bits =~ /^10/ && $state == 1) {
  	    $barcode .= 'B...';
  	    $bits = $';
  	    $state = 0;
  	} elsif ($bits =~ /^1/) {
  	    $barcode .= 'B.';
  	    $bits = $';
  	} else {
  	    die("Oops, something impossible happend!\n$bits\n");
  	}
      }
      return $barcode;
  }
  

  +

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