you could also put it in a LEGO case if you don't have a 3D printer at hand 😉

What a delightful little case! I love that. It's probably stronger than the 3D printed one, too.

Falonn wrote on 2021-10-13, 12:34:

With the adapter in the 3D printed case, I was less worried about it shorting out on anything, so it's more or less just hanging around. One more benefit of using all of the extension cables is that there is a lot of slack. You can tuck the thing just about anywhere in the case without any trouble. I'm using a CF-to-IDE adapter for storage, so the HDD cage in my case was empty and offered a nice, safe, out-of-the-way place to just leave it sitting around.

Gotcha. Having the PS2 port mounted in an expansion slot is an excellent solution. I probably still have some spare space somewhere in my case!

I've got a weird one. When using a KVM , connecting the adapter to the serial port turns the display mono.
And when I say "connecting the adapter to the serial port" I mean exactly that and only that, just the adapter without PS/2 or power cables 😂

Note that the KVM definitely is the culprit, I've been using the same PC (386, ISA Cirrus Logic 542x) with the same adapter directly connected to the same monitor for almost 2 years.
Level One KVM: https://us.level1.com/collections/kvm/products/kvm-0411

Any ideas/anyone with the same KVM to try?

This does not happen with a "Level One KVM-0212", though it's only a 2 port model.
Is it the same phenomenon if you powercycle the PS2TOSERIAL adapter and connect the mouse?

1541 wrote on 2022-01-27, 13:34:

This does not happen with a "Level One KVM-0212", though it's only a 2 port model.
Is it the same phenomenon if you powercycle the PS2TOSERIAL adapter and connect the mouse?

Ah thank you, I'd assume it's the same KVM. Yes, it's the same. So it appears to be a very special case and not some generic incompatibility.
I can't even imagine what's happening, the mouse driver notices something's wrong too

I investigated a bit more, connecting the adapter confuses indeed the monitor detection and thinks it has a mono monitor connected.
Very strange, I can't imagine what might be causing this, although it's definitely related to the KVM

konc wrote on 2022-01-28, 18:57:

I investigated a bit more, connecting the adapter confuses indeed the monitor detection and thinks it has a mono monitor connected.
Very strange, I can't imagine what might be causing this, although it's definitely related to the KVM

Connecting something to the serial ports adds load to the +12V and/or -12V line. Some VGA cards use these lines to generate the reference voltage for the RAMDAC. Monitor detection often measures the impedance of the monitor by comparing the DAC output voltage to some threshold voltage. So if (for example) the -12V is connected badly to the power supply, any notable load (even a couple of milliamps) could significantly shift the -12V level, and thus influence the monitor impedance detection. If the specific KVM in question already has an excessively high input impedance (a color monitor should have 75 ohm DC resistance on R, G, B), a tiny change on the 12V lines could tip it over the edge of detecting "no 75 ohm termination on red or blue" which indicates a monochrome monitor.

mkarcher wrote on 2022-01-28, 23:37:

Connecting something to the serial ports adds load to the +12V and/or -12V line. Some VGA cards use these lines to generate the reference voltage for the RAMDAC. Monitor detection often measures the impedance of the monitor by comparing the DAC output voltage to some threshold voltage. So if (for example) the -12V is connected badly to the power supply, any notable load (even a couple of milliamps) could significantly shift the -12V level, and thus influence the monitor impedance detection. If the specific KVM in question already has an excessively high input impedance (a color monitor should have 75 ohm DC resistance on R, G, B), a tiny change on the 12V lines could tip it over the edge of detecting "no 75 ohm termination on red or blue" which indicates a monochrome monitor.

Thank you very much for the excellent explanation. It made me understand how the detection mechanism works and dig further.

To begin with, connecting anything to the serial port, even a serial mouse, resulted in mono monitor detection. Meaning that the KVM was already at the border.

But why? Because of the keyboard, an IBM model M. I tried different keyboards with the same KVM and PS2TOSERIAL and there was no mono monitor detected again.
It appears that this particular keyboard brings the KVM to the point where connecting anything else to the serial port messes with the monitor detection.
Directly connected to the PC it's fine, add the KVM and it's not 😀 I guess my best chance now is to try a different VGA card.

Also sorry everyone for posting this in the PS2TOSERIAL thread which apparently had nothing to do with it, but before mkarcher's explanation I was only experiencing the problem when connecting the adapter.

Apologies for resurrecting an old thread!

Has anyone tried to use a USB/PS2 adapter and a USB mouse with this? It is getting increasingly difficult to find PS2 optical mice..

Thanks!

robbiesz wrote on 2023-06-23, 17:17:

Has anyone tried to use a USB/PS2 adapter and a USB mouse with this? It is getting increasingly difficult to find PS2 optical mice..

Yes, but you need an optical USB mouse that still supports the PS2 protocol internally
https://youtube.com/shorts/zV8uoAQW6NI
And
https://youtu.be/1UNOzkzLU_w
[List of working/tested models included in video description]

It worked with a USB mouse + PS/2 adapter for me. I wasn't sure whether it depended on the mouse's internals and didn't want to take any chances, so I tried to find one that included the adapter (and was close to being suitably retro looking). I ended up going with this Cherry USB Mouse: https://www.amazon.com/dp/B000E0VM26

So at a minimum, I can confirm that it works with that USB mouse.

1541 wrote on 2023-06-23, 17:26:

Yes, but you need an optical USB mouse that still supports the PS2 protocol internally

I didn't remember it was so difficult. I need USB to serial mouse. (And USB to that round IBM connector keyboard). I know it's not period correct and some may disagree but for me modern mice and keyboards are so much better ergonomically.

Received mine today but it's not working with an Aten CS64A KVM switch.

Both LEDs turn on but all mouse drivers I tested didn't find a mouse. Also tried the modified mouse drivers in this topic to no avail. Even PS2MASET.EXE doesn't detect anything when the KVM is attached. Tried setting it to 19200 baud (without the KVM connected). But when connecting the KVM again it still doesn't detect a mouse. The KVM is working fine btw. I use this KVM also with an ISA PS/2 card from another project (see: Another PS/2 Mouse ISA (ISA8) card adapter) and this works without problems.

It works without problems if the ps/2 mouse is directly connected btw. Anybody knows how to get it to work with this KVM?

Still have this issue above. Tried it with another KVM and some other mice. It's now at least seeing a mouse and all mouse drivers I tried are loading and detecting a mouse but the mouse is not moving at all in any program or game (with 1200 or 19k2 baud).

@dreamblaster: should this work with a KVM or should I do a firmware update/downgrade? Are there any other firmwares available? As it is now I unfortunately can't use it.

Yoghoo wrote on 2024-03-31, 11:59:

Still have this issue above. Tried it with another KVM and some other mice. It's now at least seeing a mouse and all mouse drivers I tried are loading and detecting a mouse but the mouse is not moving at all in any program or game (with 1200 or 19k2 baud).

Does your KVM switch support mouse protocol translation? Better ones do, simple ones just switch the mouse data without processing it. If your KVM switch does not support protocol translation, you run into issues as soon as one computer requests the PS/2 mouse to use the new "intellimouse with wheel" protocol, while the DOS computer still expects the "PS/2 mouse classic 3-button" protocol. Note that I am not taliking about USB-to-PS/2 translation, but about intellimouse-to-classic translation, two different protocols used on the PS/2 interface. In the worst case, your KVM switch forces any intellimouse-capable mouse into intellimouse mode (to make sure the mouse is in that mode, even if the switch was set to a different computer when the computer tried to initialize the mode), and expects all client PCs to handle the intellimouse protocol as well.

mkarcher wrote on 2024-04-02, 07:16:

Yoghoo wrote on 2024-03-31, 11:59:

Still have this issue above. Tried it with another KVM and some other mice. It's now at least seeing a mouse and all mouse drivers I tried are loading and detecting a mouse but the mouse is not moving at all in any program or game (with 1200 or 19k2 baud).

Does your KVM switch support mouse protocol translation? Better ones do, simple ones just switch the mouse data without processing it. If your KVM switch does not support protocol translation, you run into issues as soon as one computer requests the PS/2 mouse to use the new "intellimouse with wheel" protocol, while the DOS computer still expects the "PS/2 mouse classic 3-button" protocol. Note that I am not taliking about USB-to-PS/2 translation, but about intellimouse-to-classic translation, two different protocols used on the PS/2 interface. In the worst case, your KVM switch forces any intellimouse-capable mouse into intellimouse mode (to make sure the mouse is in that mode, even if the switch was set to a different computer when the computer tried to initialize the mode), and expects all client PCs to handle the intellimouse protocol as well.

Unfortunately can't find anything related to protocol translation in the specs for this KVM. It however will not use intellimouse with wheel for all mice. It will give the correct mouse to the pc. So I guess it's implemented.

Using this KVM for 8 pc's atm (ranging for 386 to P3) with DOS to WIN98SE without problems. Some PC's have other PS2 to serial cards (ISA) which work perfectly with this KVM.