The Dream

The dream hardware solution would be a KVM switch with the following features (basically emulating hotkeynet features)

- 5-10 port (5 man teams seem to be the most played)
- support 6+ rollover keys
- real USB emulation / pass through
- synchronous mode / synchronizer / sync mode (keys are sent to all selected outputs)
- individual buttons to turn on off outputs (sometime you want to only control 3 of your 5 clients)
- master sync mode button
- option to disable enable mouse clicks (on slaves only)
- option to disable specific keyboard keys on selected output (to deactivate WASD on slaves for example)- borderless mouse option



Google Search

I searched google for multiple hours with various keywords and looked read through any promising website on this topic.

From what I found it looks bleak ¬_¬

Hardeware Synchronizer KVM seem to be a rather niche use case. Even most enterprise solutions that cost 500-2000 USD are designed to be switches or borderless mouse solutions. None of them have synchronous mode (multibroadcasting)

Example Adder Command & Control Switch, 4 Port USB and Audio KM Switch

Instant switching with True USB Emulation

Adder's True USB Emulation technology overcomes limitations of other KVM switches by emulating the true character of the connected devices to all the computers simultaneously. This means that you can use the extra function keys, wheels, buttons and controls, without sacrificing switching times.

The cheap Aimos / FjGear / ShuOne Synchronizer KVMs for 20-40 USD and alike seem to be the only thing on the market that gets close to the dream for hardware multiboxing.

I did find some enterprise solutions that support USB pass through / USB emulation. Meaning the original Keyboard/Mouse signal is forwarded/switched without interruption to all connected output machines. But those cost 1200 USD and don't have synchronous mode.

Discription of different USB Emulation Technologies: http://www.blackbox.co.uk/_AppData/L..._Emulation.pdf


Arduino / Raspberry Pi

I also looked into creating a KVM from programmable chips.

Turns out hackers already did this with success, but the problem is that those are limited to HID Keyboard/Mouse and I couldn't find any with sync mode, only switches:

https://github.com/nathalis/Arduino-K-Switch
https://hackaday.com/2020/04/19/kvm-uses-many-arduinos
https://hackaday.io/project/6464-arduino-kvm-switch
https://hackaday.com/tag/kvm/
https://reposhub.com/python/programming-with-hardware/pikvm-pikvm.html


Where to go from here?

The best/cheapest/available solution so far seems to be 2 cheap synchronizer KVMs.
One for the mouse one for keyboard to combat the roll over and port selection limitations.To run a 5 man team, you can get by with 2x 4 port KVMs for 20 USD each, so 40 USD total.

Unless someone comes up with a solution to make USB emulation / pass through work in Arduino or a KVM enterprise decides to implement those features we are stuck with that option.