Display-switch: Turn a $30 USB switch into a full-featured multi-monitor KVM

Whoah. How do I obtain these ddc commands on macOS?

  :~$ sudo ddcutil detect
  Invalid display
  I2C bus:             /dev/i2c-1
    EDID synopsis:
    Mfg id:           AUO
    Model:            
    Serial number:    
    Manufacture year: 2009
    EDID version:     1.3
    DDC communication failed
    This appears to be a laptop display. Laptop displays do not support DDC/CI.
  Display 1
  I2C bus:             /dev/i2c-2
    EDID synopsis:
    Mfg id:           DEL
    Model:            DELL U2415
    Serial number:    CFV9N94S0Y2S
    Manufacture year: 2019
    EDID version:     1.3
    VCP version:         2.1

I have a short script that will allow me to change input on a specific display. Very handy. However please note, that while this does work for HDMI, DVI and Displayport only DVI/HDMI seems to have an active connection when another input has been selected.

That means that while I can switch to another input I can not switch back from the same computer but must install something on the other machine to give it back. This is of course exactly what the linked article is doing, but with HDMI/DVI I don't have to have that requirement. And on top of that, operating systems in general seem to believe that, when using displayport, switching to another input is equivalent to disconnecting the display altogether and thus remove it and rearrange windows etc. Insanely frustrating.

Again, no problem with HDMI/DVI. So although Displayport is a much better interface and I've been a strong advocate for it, these issues makes me hate it with passion.

DDC can also be used to change display brightness, which in my opinion is way too cumbersome to do manually (especially if you have more than one display).

  #!/bin/bash
  ddcutil setvcp 60 0x11

  "C:\Program Files (x86)\Dell\Dell Display Manager\ddm.exe" SetActiveInput DP

So for linux (e.g. fedora):

  dnf install ddcutil
  ddcutil capabilities -d 1 # show the available commands
  ddcutil setvcp 60 0x11    # for example switch to HDMI 1
  # assign a global shortcut key to the `ddcutil setvcp` command you need

  - download the "Dell Display Manager" software from their support site
  - assign a shortcut key in the Dell Display Manager: "Input Manager" tab => "Favourite Input Shortcut Key"

Any idea why?

I use two capture cards and them on th bottom monitors when needed (use 4 screens). This way I can also easily stream and records the screens when on a meeting that is on another machine.

One pro is that it's able to get power from any of the USB inputs, so no extra cable!

One con is that for some reason it only does USB 2...

Amazon FR link : https://www.amazon.fr/gp/product/B08Q7J3B82

There's plenty of different hardware out there but not a whole lot of reviews; and my experience with the HDMI interface has, on the whole, not been the best. HDMI is great for consumer stuff, and for plugging in a generic source to a screen (AppleTV, Firestick, Xbox, cable box, etc) -- but, as soon as you want to do anything even slightly more advanced, you often run into hiccups quite rapidly (EDID & handshake/negotiation issues, cable & port quality, HDCP, etc).

I have several 'screens' (TVs) and I wanted to be able to mirror my 'main' display to other screens on occasion, for instance. It's easy to do that with a cheap-ish "splitter" [though they are finnicky), but if you want to "scale" that at all then you rapidly run into proprietary and/or high-cost solutions or have to make substantial quality & capability concessions (and >=10G LAN connectivity is pre-existing).

I was annoyed by the lack of good options & and the extreme prices and/or the limitations of the options that do exist -- enough so that I'm working on (and already actively using) my own IP-based "video distribution" solution, heh.

Would you care to post the brand and serial for the matrix?

I will never buy Samsung or LG again - the displays themselves were great but the UI/UX for switching inputs and brightness etc are simply too excruciating.

One second latency ... not ideal.

Is there any way to sleepwait on a USB config change instead?

[EDIT]: this might help:

https://stackoverflow.com/questions/469243/how-can-i-listen-...

I also have a few PCs and use the input selection on my monitor to achieve the KVM aspect. The only issue I found is that if no monitor is actively connected to a windows machine, barrier server doesn’t work well, and also you can’t Remote Desktop to it. I solved both of these by adding a dummy HDMI dongle, set to a low resolution so application windows can’t get stuck there.

Not a perfect solution but the best I’ve found since my goals were: to use a Bluetooth keyboard and mouse, and not worry about limitations to refresh rate, etc.

Installed on macOS 12.1 and Windows 10 or 11, and nothing happens!

It sees the client and server just fine. But never moves over!

Maybe I should the try the paid Synergy!

The Logitech solution has the lag when you bang against the side of the screen, and thats no good! :-)

https://github.com/input-leap/input-leap/issues/1414

Reminds me of an i2c motor controller I bought years ago, based off some avr microcontroller. I spent an afternoon trying to understand how I'd hooked things up wrong, trying to understand why I couldn't read the control values. Turns the soft i2c interface just didn't implement reading values off the controller at all, but served ok if I treated it as a write-only device. Frustrating tricky devices. Sometimes they lie.

But yeah, also a >15% chance your monitor doesn't support switching inputs via DDC/CI. Would be so nice if review sites would cover this sort of thing. As it is, it's just a tech-secret, something invisible to the market, no push to include it, no points deducted for getting it wrong/bad. It leaves a lot of room for the situation to sit & not improve. Better reviewing would help move things along.

You could probably get that result at the moment using the external command feature and something like xdotool (on Linux)

One of the computers is a work issued laptop and with this solution i won't have to install any software.

The monitor is rather slow to switch inputs, but otherwise all is good.

The only visible thing on the desk is the button for switching USB devices.

This is something the industry should address. It's ridiculous.

It also seems like you can switch from any computer currently connected. Have your normal computer switch to the other computer's input.

I'm using this command

sudo virsh start win10;sudo ddcutil -d 1 setvcp 0x60 0x03

To start Windows and change display input to DVI, which is the GPU for my Windows VM.

Changing back can be done either by powering the VM down or running the command

sudo ddcutil -d 1 setvcp 0x60 0x0F

It needs to run on each computer in the setup since it watches for the USB devices to connect.

https://duckduckgo.com/?q=usb+switch

This device switches your keyboards and mice and so on between two computers. The software in OP reacts to these events and switches monitor inputs using some equivalent of HDMI CEC called DDC/CI.

[0]: https://smile.amazon.com/Switcher-Selector-Computers-Keyboar...

I dunno man, this worked pretty ok for me:

> This utility watches for USB device connect/disconnect events and switches monitor inputs via DDC/CI.

And then a couple lines latter, a sample config that makes it pretty obvious how simple this goes:

> usb_device = "1050:0407" \ on_usb_connect = "Hdmi1" \ on_usb_disconnect = "Hdmi2"

Plug in a device & switches to hdmi1. Unplug & it switches to hdmi2. A USB switch is optional, one could just move where they plug their mouse into by hand, for example. But you don't seem to be interested in helping fill yourself in on anything here, on learning, on using search engines to find anything out. Honestly filling in the neophyte knowledge like that is not what project descriptions are for, in my book.

Generally, dude: relax, chill out. Most everything on this planet could use better description. But this seemed pretty clear & simple to me, at least. I think it'll work for a lot a lot of people as is. No need to be aggressively rude. Have you ever dealt with any kind of soft-kvm like technology before? Perhaps people would more self-select into this kind of project, versus rando's walking in on the street. I think that's ok.

The USB switch button will send a connect/disconnect event to both computers and they will then react accordingly.

When you press the button on the USB switch to go to another PC, the software detects this and sends data commands over the monitor connection (using DDC standard) to trigger the monitors to switch inputs. You can use this same data communications standard to do things like adjust the brightness of your display. For example, I have these setup on my Mac to adjust the brightness of my two attached displays (complexity increased with multiple displays and desire for each to change at same time, simpler commands with a single display):

alias day="seq 3 | xargs -n 1 -P 3 sh -c 'ddcctl -d \$1 -b 80' sh" alias evening="seq 3 | xargs -n 1 -P 3 sh -c 'ddcctl -d \$1 -b 32' sh" alias night="seq 3 | xargs -n 1 -P 3 sh -c 'ddcctl -d \$1 -b 10' sh"

Does that make sense? As mentioned earlier, you're limited by the minimum number of inputs on the monitor(s) and/or the minimum number of computers the USB switch can be connected to. The simplicity of this system is that the display connections do not go through any switching layer and are instead directly connected to the computers (which avoids a number of compatibility issues).

I should be clear that I haven't used this yet but I'm going to try it. The Acer monitors I'm using have two HDMI ports and 1 DisplayPort so I can in practice attach 3 computers assuming I buy a USB switch which can connect to 3 or more computers.

If you only want a single monitor, there are switches that also switch between different video inputs. These are commonly referred to as "KVM switches" (KVM being Keyboard, Video, Mouse.) But KVM switches cost more money...

My understanding is this project allows you to use a plain USB switch and the multiple video inputs on your monitor to simulate a full blown KVM switch.

https://news.ycombinator.com/newsguidelines.html