Learning to Reverse Engineer on a Broken Printer

Lexmark Hack

When a Lexmark inkjet printer stopped working, [Mojobobo] was able to claim it as his own. He quickly realized that the machine was flooded with ink and not worth repairing, but that didn’t mean he couldn’t still find a use for it. When he learned that the printer’s firmware was not only upgradable but also unprotected, he knew he should be able to get the printer to do his own bidding.

[Mojobobo] started his journey with the motherboard. The unit still powered up, but it was asking to insert a “duplex module” before it would boot any further. [Mojobobo] first tried to find a way to trick the duplex module sensor, but was unsuccessful. His next step was to search for some kind of serial communications port. He didn’t have an oscilloscope, so instead he used a speaker with a wire probe. In theory, if the wire was pressed against an active serial port, he would be able to hear varying tones through the speaker. Sure enough, he found some interesting tones after probing around some ports next to a “JTAG” label. He looked up some information about the nearby chip and found that it included an SPI bus.

After some internet research, [Mojobobo] learned enough about SPI to have a rough idea of how to use it. Having limited tools available to him, he decided to use his Arduino to try to communicate with the motherboard. After wiring up a simple circuit, (and then re-wiring it) he was able to dump the first 4096 bytes of the motherboard’s boot loader to the Arduino via the SPI interface.

[Mojobobo's] next steps will be to find a faster way to dump the boot loader. At 9600 baud, he grew tired of waiting after three hours. Once he has the full boot loader he intends to search for a way to bypass the duplex sensor and get the board to finish booting. Then he may just use the printer for its scanning functions, or he might find other interesting uses for it.

Free Linux computer from a printer’s WiFi card

Whether it’s building a 3D scanning system with a Kinect, or using a USB TV tuner dongle for software defined radio, there are a lot of interesting off-schedule uses for commodity hardware. The latest comes from the fruitful mind of [sjMoquin] and a Lexmark N2050 WiFi card that runs Linux.

This build started off with a Lexmark X6570 all-in-one printer available for about $100 USD on eBay. This printer comes packaged with a Lexmark N2050 WiFi card running BusyBox. After soldering a few wires to the USB/UART pins on the N2050, [sjMoquin] had a very cheap but highly useful single board computer running Linux.

There is still a little more work to be done – the WiFi and USB on the N2050 aren’t currently supported. [sjMoquin] and [Julia Longtin] are working on that, so a fully functional embedded Linux board based on a printer’s WiFi card should be available soon. It might be time to hit up eBay for a few of these cards, you know.

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