Printer Hacking!
This info may seem a little out of place on this site, but some of you might find something educational in it. The EPROM character data from my printer was dumped and edited, and stuffed back into the printer.
In laymans terms, I modified the characters:
I went from this:
to this:

One day at work I decided our receipts were boring, so I set about sprucing them up with some keen ANSI boxes and lines. After a few minutes with my favourite DOS text editor, I printed a sample receipt and was horrified to learn our printer, a venerable Citizen iDP3540, didn't have an ANSI character set! Yanking the thing open, I pulled out the only socketed chip - a 256 kilobyte (32k) EPROM (Erasable Programmable Read Only Memory) and slapped it on ye olde EPROM reader. Dumping the contents and viewing them with a hex-viewer (shows data in hexadecimal notation) I was presented with this:

[- Hex Editor Screenshot -]

Naturally this didn't impress me, so I put this program, Tile Layer, to good use. Originally written to edit character set data when translating Nintendo ROMs, this program displayed the printer's EPROM data as a bitmap picture with a bit-depth of 1 (ie, two colours). It looked kind of like...

[- Tile Layer Screenshot -]

It was kind of odd, each character was duplicated twice, with only half of the character on each tile. It was a relatively simple matter to replace the characters in the EPROM with ones of my own creation. I burned a new ROM, put it back in the printer, and presto! New characters!

[- Overview -]
Here are some of the changed characters,
including the nifty new 'E'

As you can see, the new fonts worked well but didn't touch vertically - something that I simply can't change by editing the character data. That unfortunately means I can't use the new character set - they look crappy. Feel free to download the ROM and Tile Layer software and hack away. If you come up with a decent new character set (don't touch the garbage-looking data!!!) email it to me!

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