Experiment 1

A project log for EDIDone - Disable DisplayPort Hotplug

Tired of computers rearranging your screen when monitors turn off? I am.

Torbjörn LindholmTorbjörn Lindholm 04/12/2021 at 18:450 Comments

After hacking up a DisplayPort cable to bits and wiring up headers, I discovered that in most cases the EDID stream is not used (or I suck at triggering it)

I did discover that whenever the display is on, the HPD pin is at 3.3V. 

Here's the logic analyzer screenshot (if you can call this "logic")

Edit: Looks like this cable only has CONFIG wires broken out. I need to investigate further.
Edit 2: Well, no dice. Still no stream.

I'm tapping into these pins:

So far, I only saw the Hot Plug pin going high and low when it's switched on and off, and I was unable to capture anything on Pin 15 and 17.

The wiring looks like this (Basically everything is a passthrough, and I'm tapping off of those 4 wires, and there are 1.5K resistors in series so I don't accidentally fry the card should the probe touch the ground and the pin at the same time)

One interesting observation is that if I connect the logic analyzer (a cheap Saleae USB logic analyzer clone), the computer thinks there's still a display connected, even if the cable is disconnected. So if all fails, I could simply tap off of unused Pin 20 for 3.3V, insert a resistor between that and Pin 18, and pass everything through...
(Also sorry for all the little updates flooding the feed, I forgot to uncheck the little checkbox that does the stuff)