printer cartridge memory

[deadshort]

My printer died today with the error print cartridge incompatible, had been working ok for some time. To cut a long story short it was a bad connection on one print cartridge and it now working. But it got me wondering how dose it all work? The faulty cartridge is a cheap one not the genuine Epson one. I think, please correct me if I got this wrong, when a cartridge is printing the printer increments a counter in the cartridge when the printer reads the cartridge and the counter has reached a set count the printer sends to the computer out of ink.
so how dose this work? are all the cartridges on the same data bus with address for each colour?  How dose a cartridge chip resetter work? 

[Alexei.Polkhanov]

I would start by connecting it and sniffing communications between printer and cartridge with an oscilloscope/logic analyser. You may want to try men-in-the-middle attack of some sort afterwards. These cartridge/toner riddle problems can be a lot of fun to solve! Just check online to make sure someone did not do it already for your printer model.

[amyk]

Been done before for older Epson at least, it's a serial EEPROM: http://www.eddiem.com/photo/CIS/inkchip/chip.html

More recent work here (note that it references a patent containing the details of the proprietary protocol):
http://www.instructables.com/id/Reverse-Engineering-to-Emulate-Ink-Cartridges-for-/

[fluxcapacitor]

You can get some software for older epson printers that can reset the counters,amongst other things .

http://www.ssclg.com/epsone.shtml

[Stonent]

Lexmark used to have so-called Pre-Fill cartridges for laser printers.  (I'm not sure if they still do).

They would sell you a cartridge at a much lower cost if you sent them back your old one, but the catch was the serial EEPROM on the cartridge would tell the printer to stop printing after a predetermined number of prints no matter how much toner was left.

I used to just pop-off the board and replace it from another cartridge that was empty but wasn't a pre-full. Or remove the toner "tank" and mate it to another cartridge.  Lexmark (and Dell) used the same cartridge designs for their laser printers but had a different part that fit a keyed slot so you couldn't fit it in.  But the keyed part was easy to remove and I used to use really old 12PPM toner on 24PPM prints with no issues.

[deadshort]

Thanks for all the reply's. I found all very interesting but the link to the reverse engineering in particularly was very interesting and more complicated than I thought. 
http://www.instructables.com/id/Reverse-Engineering-to-Emulate-Ink-Cartridges-for-/
tnx Andy