KVM Daisy Chaining Restricted to Either HID or USB3 devices

KVM Model:

MKAG-8KT3124 - 2 monitor, 4 port HDMI 2.1 KVM

USB Interface (5-gigabit or 10-gigbit):

USB 3.2 10gb


Problem:

Slave KVM restricted to either HID or USB3 devices.

Other Notes:

This is not necessarily a problem with the KVM, but I am curious if there is a workaround. I want to use the master KVM for all USB peripherals (keyboard, mouse, webcam, etc.), but it seems this is not possible as the connection from the master KVM to the slave KVM must be on either a slave HID or USB3 port. I suppose this functionality would require the KVMs to have both HID and USB3 ports on the back for each PC (labeled Up[1-4] in the manual).

Can you explain more about how you have these KVMs hooked together?

Sure, I have my keyboard and mouse connected to the master KVM via the HID ports (not the keypad one). Hotkeys work just fine on the master KVM. I then connect the PC port 1 USB3 on the master KVM to the slave KVM HID port. Hotkey HID passthrough works fine on the slave KVM, i.e. I can control the master KVM with right-ctrl and the slave KVM with left-ctrl hotkeys.

Unfortunately, it seems I cannot use non-HID-compliant peripherals through the master KVM in the setup described above. For example, if I connect a USB3 peripheral (like a webcam) on the master KVM, I would expect the slave KVM PC to recognize it, but it does not. This does work if I connect the master KVM to the slave KVM over USB3, so it seems one must choose for the master-to-slave connection either the slave HID port with slave hotkey support and HID-only devices or USB3 port without slave hotkey support and with USB3 devices.

Since these are the HDMI 2.1 KVMs, have you considered using the RJ11 port to control/switch them both with serial commands?

You could use something like a Raspberry Pi Zero or similar SBC (easiest option) or use a microcontroller to build something more bespoke.

I was thinking about the serial port. It seems to be either a custom build for this purpose or just use the front buttons to swap if I want USB3 peripherals, though I much prefer the keyboard hotkeys as I can have the KVMs out of the way. I don’t know much about the USB protocol, nor hardware interfaces, but it’d amazing if one could toggle the hotkey functionality over USB3 as opposed to just HID with a software solution. I absolutely love these L1 KVMs. They work super well with short, quality cables (Club3D, Cable Matters) when daisy chained.

I’m just guessing here, but I assume the problem is that although the first KVM sees a regular HID device from the keyboard, whereas the second chained KVM sees a USB hub with a mix of HID and non-HID devices, which is why it’s ignoring switching commands. You might also run into the limit of how many USB hubs can be daisy-chained off one-another on some computers (especially laptops with docking stations, although that’s separate to switching issues on the KVM).

If you don’t want to get into serial control, another option that might work (kind of crazy, but just throwing this out there to consider) is to take a pair of cheap AliExpress programmable keypads, and keep the logic board from each of them, one going to each KVM over USB as the keypad input, but wire up just a single set of keyswitches so that each key press sends the same command to each board.

What is the use-case for chained KVMs? Is there a reason you can’t plug the USB 3 devices directly into the “slave” KVM?