this post was submitted on 09 Nov 2025
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How to reverse engineer USB HID on Linux (popovicu.com)
submitted 14 hours ago by cm0002@europe.pub to c/linux@programming.dev
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I recently added a UPS to my server rack to keep my internet and home network running during a power outage. After unpacking it, I investigated its USB port and discovered it wasn’t for powering other devices. Instead, it connects to a host computer to provide information like battery charge status, remaining runtime, and current load.

I wanted to access this data without relying on third-party software, so I decided to see if I could reverse-engineer the protocol using Linux.

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[–] jqubed@lemmy.world 2 points 13 hours ago (1 children)

I had an old one that was DE-9!

[–] curbstickle@anarchist.nexus 4 points 13 hours ago (1 children)

I still have a 9 pin serial UPS! Its hooked in a portable rack (dont ask) at my office. Mostly because nitwits kept hitting the buttons on what amounts to an expensive IP controllable surge strip, and turning off devices on me. So now it detects and sends me a message so I can turn outlets back on.

But hey, it still sees use!

[–] frongt@lemmy.zip 2 points 26 minutes ago (1 children)

Actual serial, or that almost-serial that will shut down the UPS if you plug a serial cable in?

[–] curbstickle@anarchist.nexus 1 points 22 minutes ago* (last edited 18 minutes ago)

LOL actual serial

I've replaced the battery in that sucker more than a few times

Edit: its an old HP powerwise for the record, I think its 2 pins for serial, 6 for contact closure.