this post was submitted on 09 Nov 2025
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How to reverse engineer USB HID on Linux (popovicu.com)
submitted 17 hours ago by cm0002@europe.pub to c/linux@programming.dev
15 comments fedilink hide all child comments
 

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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[–] frongt@lemmy.zip 2 points 2 hours 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 2 hours ago* (last edited 2 hours ago) (1 children)

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.

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

Ah okay, it was APC that had the UPS with the "serial" port.

[–] curbstickle@anarchist.nexus 1 points 2 hours ago

The dumb "on battery" cable, what a joke that was