How do I create a GS1 DataBar Expanded barcode?

Question

I need to create a GS1 DataBar Expanded (RSS Expanded) barcode using either a Code128 font or a simple binary barcode font.

I'm aware of how to use the application identifiers or creating check sums but I don't know how to encode the data for the GS1 DataBar Expanded.

I've also successfully created GS1-128 (UCC / EAN-128) barcodes with the information I found here http://www.gs1-128.info/ and here http://www.barcodeisland.com/code128.phtml but these barcodes are not the same as the GS1 DataBar barcodes.

The GS1 DataBar Expanded uses some "Finder Patterns" and "Left Guard" + "Right Guard" as start / stop symbol but I can't find any information about how they are created (like binary values). http://www.onbarcode.com/gs1_databar/

How a EAN-128 looks for the number (01)12345678901231:

How a GS1 Data Bar Expanded looks for the number (01)12345678901231:

So, how do I encode my data to create an GS1 Data Bar Expanded barcode?

Answer 1

Unlike simpler barcode symbologies such as those based on Code 128 where the data is laid out as discrete bar patterns in order of the data characters, in the GS1 DataBar family of symbologies the data is diffusely spread throughout the bars.

Therefore the only way to encode the message data into bar patterns is to follow the complex procedures defined in the GS1 DataBar specification (ISO/IEC 24724), then to lookup the appropriate font glyphs which when concatenated will produce the required bar pattern.