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Hi all,

I have no idea what I'm doing and don't expect an answer, but general nudges in the right direction.

I have a specialised piece of equipment (ddg search shows nothing for model no.) that keeps track of the number of "uses" each accessory has left, and you're forced to buy another one when it runs out. Basically like a printer and ink cartridge.

The two ways I can think that it's doing this is that either the counting is being done on the machine itself or the counting is being done by a chip on the accessory, I'm banking on the latter otherwise you'd be able to share one accessory between two machines.

Does anyone know how people went about defeating/hacking/resetting ink cartridges back in the day?. So that I have somewhere to start from? I think it's do-able because we're not talking HP that have the motivation or need to have extreme encryption.

Hi all, I have no idea what I'm doing and don't expect an answer, but general nudges in the right direction. I have a specialised piece of equipment (ddg search shows nothing for model no.) that keeps track of the number of "uses" each accessory has left, and you're forced to buy another one when it runs out. Basically like a printer and ink cartridge. The two ways I can think that it's doing this is that either the counting is being done on the machine itself or the counting is being done by a chip on the accessory, I'm banking on the latter otherwise you'd be able to share one accessory between two machines. **Does anyone know how people went about defeating/hacking/resetting ink cartridges back in the day?**. So that I have somewhere to start from? I think it's do-able because we're not talking HP that have the motivation or need to have extreme encryption.

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[–] • 5 pts

You reverse engineer the circuit by connecting a wiring harness to the chip in such a way you can connect an oscilloscope to watch the communications between the chip and the device. There will be two pins, one for ground and one for the supply voltage (usually 3 or 5 volts). The other pins will be used for digital signals. Now is where it gets interesting. The chip will use some kind of protocol to communicate various pieces of information to the main device. It could use I2C bus, which means there are 4 pins SDA, SCL, VCC, and GND. I already talked about VCC: supply voltage and GND: ground. SCL is the serial clock used to synchronize the data coming over the SDA pin. The chip could use SPI bus. This uses 5 pins + VCC + GND. And it could use a proprietary data bus.

Sounds like an interesting puzzle. Good luck.

[–] • 1 pt

Very late reply on my behalf but thanks for this information, it was exactly what I was looking for.

All the expired attachments (zero uses left) were thrown out, so I'm waiting for one to become available so I can physically crack it open and see what I'm dealing with.

I have a tonne of questions, but I want to try and figure it out on my own. I've been reading up on i2c basics because I am way out of my depth on this one.

Actually, can I just lay out my strategy and get your quick feedback?

1) Find out what signal it's using, hoping it's ic2 and not something crazy. 2) Intercept the connection somehow and use an oscilloscope or some other tool to read the raw data being transmitted to the attachment in its idle state. 3) Read what data/signal is transmitted during a use case. 4) Find some way to block/overwrite the use case signal with whatever it had in its idle state so that the machine doesn't count it.

Thanks again for your reply, [I think] it's set me on the right track!

[–] • 0 pt

Yes. No problem. You're on the right track.