I Spent $4 in AI Tokens to Avoid Buying a $10 HDMI Switch (And It Was Worth It)

A journey into DDC/CI — the remote-control protocol that has been hiding inside your display cable for over twenty years, and how it turned my monitor into a KVM.

The desk that started it all

My setup looks ordinary: a MacBook Air open on the desk (my primary machine), and an LG 32UN880K — a 32" 4K monitor with two HDMI ports, DisplayPort, and USB-C. The less ordinary part is behind the MacBook: an ASUS gaming laptop running Linux whose internal screen died. It now lives as a headless tower. The external monitor isn't an accessory for it; it's the only display it has — BIOS, boot menu, everything.

Keyboard and mouse were already solved: Input Leap, a software KVM, lets me type on the ASUS using the Mac's keyboard and mouse. The unsolved problem was the dumbest one: switching the monitor between the two machines. The LG's physical OSD button works, but with several switches a day I could feel its lifespan ticking away under my thumb.

Spoiler: the monitor turned out to speak its own private dialect, and figuring that out is most of this story.