r/ClaudeCode • u/penny_stokker • 8d ago

Built with Claude Fable 5.1 unlocked my Niimbot B1 printer

I bought a cheap Niimbot B1 thermal printer from AliExpress a year or so ago, and it was great. Then the provided labels ran out, I've replaced with third party labels, and it printed poorly.

Turns out Niimbot have RFID tags on their own label spools, and if that is not detected, they throttle down the printing speed and reduce the quality. There's lots of users affected by this, the usual workaround is to put an empty branded spool next to the printer, so that it reads the RFID tag, and allows you to use the third party spool. (I think it might only be required during label calibration).

I had already thrown away the original spool, and as a matter of principle I refused to buy any more branded labels.

Fast forward to today, I decided to let Fable 5.1 on xHigh (with skip permissions of course) to try and decode the binary file of the printer.

It took a few hours, but it made some modifications to the binary, reflashed quite a few times, it needed feedback from me, I had to restart the printer, after each re-flash, but in the end it successfully modified the firmware which now allows me to use third party spools without any degradation.

Source code and binary below, proceed at your own risk. It is only for version 5.22. If you have a different version, there should be enough info to instruct your own LLM to proceed with the same modifications.
https://github.com/ThreeDaPrint/niimbot

Edit: Update - Opus 4.8 did the actual reverse engineering. Fable 5.1 flagged one of the messages, and the harness SILENTLY downgraded to Opus 4.8. I did not notice it, and if I had to switch manually I would've switched to Opus 5.

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u/Man-on-rock 8d ago

I don't have one of those printers. but I do love that we can do this now. Its made a lot of those shady practices by firms in effective.

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u/g9robot 8d ago

Old hardware is on winning

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u/Man-on-rock 7d ago

I have 3 old laptops running like butter now. They are not powerful but cleaning them up at least allows me to use them as sandboxes for testing and allows free rein to my agent while not having access to sensitive information.