MiSTer FPGA Forum

Can anyone explain why KVM switches and the MiSTer don't seem to work well together? Or recommend one that does actually work properly with a MiSTer system?

I posted a question in the Newcomers section about my MiSTer (it's part of a MiSTer Multisystem setup) not playing sound if connected through a KVM switch via HDMI, or not displaying video if I set dvi_mode=0. Then using a different KVM switch it all worked, but I lost the sound on my PC.

Now I've found another issue which has turned out to be related to my USB joystick. When I turn on, or reset the MiSTer, I get random repeated keyboard "presses", or missed keyboard presses, so basically everything goes haywire. You might get constant scrolling of a menu on the OSD, or just endless repeat characters when typing in a computer core, or missed characters. In the end I just started disconnecting things from my setup one at a time until I disconnected the USB joystick, which is connected to the KVM switch, and then everything worked fine. A bit more experimenting and I've discovered that this happens ONLY if the joystick is connected to the KVM switch AND the power is cycled to the MiSTer. If I plug the joystick straight into a MMS USB port, no problems. If I switch the KVM switch to my PC, then switch it back to my MMS while the MMS is powered on, no problems! Thing is the KVM switch where I had the HDMI / sound issue doesn't have the joystick / key press issue, so it's obviously not the case that this problems occur with all KVM switches. But so far I've been through 3 switches and they've all had one of these problems.

I'm currently in a very confined space so I'm not able to have multiple setups with multiple keyboards and monitors so some kind of switching system is really my only solution. Anyone got any recommendations on a decent switch that actually works properly with a PC and a MiSTer and includes USB, video and audio? Or am I looking at a 2 switch solution, one KVM and one audio? All my devices have 3.5mm audio outs so I could make that work it just takes up more space and is less tidy, but I'd prefer a single switch solution if possible.

I have a "tesmart" 8x hdmi kvm switch, connected to several things including my mister, and it works fine as it should. After it i have an hdmi extractor to get toslink audio, then an hdmi to vga dac, and everything work as it should. Even the emulated keyboard / mouse is working fine.

I have a USB3 switch... i.e. it does not have viseo. But it works fine. I use a separate switch for VGA in reverse (i.e. single source from MiSter into either a monitor or a capture card)

I have a Gigabyte monitor with built-in KVM. Connected PC, Mister and PS5. Everything works as intended.

Newsdee wrote: ↑Sun Oct 15, 2023 9:55 am

I have a USB3 switch... i.e. it does not have viseo. But it works fine. I use a separate switch for VGA in reverse (i.e. single source from MiSter into either a monitor or a capture card)

I also had a USB 3 switch that worked fine, but it's when I moved up to a KVM switch with audio that I had all these problems.

Atohmdiy wrote: ↑Sun Oct 15, 2023 8:44 am

I have a "tesmart" 8x hdmi kvm switch, connected to several things including my mister, and it works fine as it should. After it i have an hdmi extractor to get toslink audio, then an hdmi to vga dac, and everything work as it should. Even the emulated keyboard / mouse is working fine.

I suspect the optical output of my KVM switch may be working as I can select it from my RealTek Audio Manager so I could maybe go to a DAC, but I can't test it as I have no DAC yet to connect to the switch. It's just it would be an extra expense as the 3.5mm audio out should work. I see the TESmart switches are quite a bit more expensive than the ones I bought so there may be a difference in quality there. There's a 4 port one with audio that looks ideal except it's over £400 so it's pretty steep. I'm think I may end up having to go with a 2 box solution, KVM + audio box to get what I want to stay within a more reasonable budget.

emiliom wrote: ↑Mon Oct 16, 2023 11:31 am

Atohmdiy wrote: ↑Sun Oct 15, 2023 8:44 am

I have a "tesmart" 8x hdmi kvm switch, connected to several things including my mister, and it works fine as it should. After it i have an hdmi extractor to get toslink audio, then an hdmi to vga dac, and everything work as it should. Even the emulated keyboard / mouse is working fine.

I suspect the optical output of my KVM switch may be working as I can select it from my RealTek Audio Manager so I could maybe go to a DAC, but I can't test it as I have no DAC yet to connect to the switch. It's just it would be an extra expense as the 3.5mm audio out should work. I see the TESmart switches are quite a bit more expensive than the ones I bought so there may be a difference in quality there. There's a 4 port one with audio that looks ideal except it's over £400 so it's pretty steep. I'm think I may end up having to go with a 2 box solution, KVM + audio box to get what I want to stay within a more reasonable budget.

The tesmart come with two version if i recall. One support a newer hdmi version and hence better bandwidth. This "better" version is useless as i'll never throw more than 720p. So i have the "lower" version that is around 200€.
After this switch you can use any hdmi extractor that already include a DAC (if you don't care the low quality) or with an spdif/toslink output to use a dedicated dac. In my case i make a lot of hifi diy, so i build a small system for my retro setup with spare parts, that include the speakers, power amp and a DAC with spdif/toslink input and volume control. The kvm switch is great as i can switch the audio / video and controller all at once.