HP-41 Bar-Code checksum algorithm.

[Diego Diaz]

Hi again!

Does anybody here know how is the HP-41 Bar-Code checksum calculated?... (And wants to share this info :-)

Thanks in advance.

[Vassilis Prevelakis]

The "Make You own HP41C Barcode" Manual is included in the MoHPC CDROM collection. The Basic programs are essentially unreadable (what a horrible language), but the algorithms and flowcharts are all there.

The manual is in file packs/hpbc.pdf

**vp

[Tony Duell]

My 'LIF Utilities for Linux' package includes programs to produce HP41 program and data barcode, and of course they calculate the checksums. These programs come as (hopefully) commented C
source code, so you might be able to figure out the algorithm from there. It'll make more sense if you have the 'Create your own HP41 barcode' book, though

[Diego Diaz]

Hi!

Thank you both for your comments. Finally I've got the desired algorithm and... it was here at MoHPC!!:

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=42

An article posted by Dan McDonald (my gratitude for him), wich includes an Excell file "HP_ListA.xls" with an annotated macro for the barcode generation.

The "real thing" is fairly easy: (sum of bytes 2-16 (or the last byte if less in row) + previous row checksum byte) MOD 255.

Again, thanks and cheers from the middle of the Athlantic Ocean ;-)