Looks like a great idea for those older systems so you dont have to be stuck with a serial ball mouse.

Great idea. I hate the way the external solutions stick out a long way behind cases and get too easily damaged.

Just one issue:

I mean, you are going to want to use a relatively modern USB mouse with PS/2 -support rather than an actual vintage part, right?

No, I'm going to connect it to a KVM switch with PS/2, I hook up the "relatively modern" Trackball Explorer to that. So I still need PS/2.

dionb wrote on 2026-02-14, 15:16:

Just one issue:

I mean, you are going to want to use a relatively modern USB mouse with PS/2 -support rather than an actual vintage part, right?

No, I'm going to connect it to a KVM switch with PS/2, I hook up the "relatively modern" Trackball Explorer to that. So I still need PS/2.

Obviously it still uses PS/2 protocol rather than USB, it just has USB A connector instead of 6 pin mini-DIN. You can either attach a PS/2 panel to the header or use an PS/2->USB passive adapter.

this sounds like a great project! having trouble with serial ports on different boards myself and lack of compatible ps2 mice, i will watch this progress definitly.

I think that I got it working as a wheel mouse as well.

Btw, if somebody wants to test this, I still got a few PCBs and parts for them. But keep in mind that this is a prototype, so you need to be comfortable with soldering and programming the microcontroller via SPI header.

no offense to the project but at this level of complexity and effort of assembly why not just build rio444's ISA card?

maxtherabbit wrote on 2026-02-15, 15:46:

no offense to the project but at this level of complexity and effort of assembly why not just build rio444's ISA card?

That would have also been an option, but this doesn't use an ISA slot, and it's really very simple. It only uses a very simple microcontroller and a level converter instead of a more complex chip like EPM3064 and an Atmega8, and assembling it is about as easy as soldering gets. Plus I felt like tinkering a bit and doing my own version. 😀

Also, rio444's project is not open source as far as I know. I'm planning to publish this once its ready and I figure out what licensing scheme to use and so on.

I have tested this with the two PS/2 compatible mice that I have, both of them USB with PS/2 support, in DOS with CTmouse and in Windows 95. So far it seems to work well, I'd say this is as far as I get in testing with the devices I have at hand.

Also, I assembled two more prototypes in case some daring person, preferably in EU so that postage stays reasonable, wants to buy them for trying them out. If I make a V2 of the PCB, some more elegant mounting scheme is definitely needed. Anyways, these are ready for use, but you'd still need to be able to flash the microcontroller through SPI in case bugs are found and a new software is needed.

Btw, why can't I edit posts? This is a bit inconvenient as I'd like to add info to the first post.

maxtherabbit wrote on 2026-02-15, 15:46:

no offense to the project but at this level of complexity and effort of assembly why not just build rio444's ISA card?

That card requires an obsolete CPLD that can be difficult to find from a reputable source.

Wrong. I have updated the design and binaries to work with a current production CPLD. It's all in the thread

It looks like I missed quite a few developments since I read through that thread last summer.

Rio444's ISA card's main advantage is that it doesn't need modified mouse drivers to achieve low latency, right? Otherwise there shouldn't be that much difference between different adapters.

Mike_ wrote on 2026-02-19, 07:09:

Rio444's ISA card's main advantage is that it doesn't need modified mouse drivers to achieve low latency, right? Otherwise there shouldn't be that much difference between different adapters.

Probably not that much. But if you're using a KVM it is a different story. A lot of the existing adapters don't work correctly when using a KVM. Or only work with certain KVM's. I tried a couple of them (internal and external). And the only one that worked all the time was the one from Rio444.

akimmet wrote on 2026-02-19, 04:37:

It looks like I missed quite a few developments since I read through that thread last summer.

the instructions for using the ATF1504AS are all in this post, if you'd like to try it I can DM the SVF file
Re: Another PS/2 Mouse ISA (ISA8) card adapter

Yoghoo wrote on 2026-02-19, 08:37:

Probably not that much. But if you're using a KVM it is a different story. A lot of the existing adapters don't work correctly when using a KVM. Or only work with certain KVM's. I tried a couple of them (internal and external). And the only one that worked all the time was the one from Rio444.

Hmm, that's interesting. I guess it could be signal integrity issues, but I doubt it. Probably Rio444's implementation is just better at handling hotplugging, which happens regularly with a KVM switch.

I'm intending to support hotplugging with this adapter. But I don't have a KVM switch to test with. What kind of issues there have been when using regular adapters with them, have the problems occurred when switching?

From my experience the issue with a KVM is loss of synchronization or lag. The mouse cursor movements will be delayed by at least .25 seconds, with periodic dropouts.

akimmet wrote on 2026-02-23, 22:13:

From my experience the issue with a KVM is loss of synchronization or lag. The mouse cursor movements will be delayed by at least .25 seconds, with periodic dropouts.

That sounds like it could be that the adapter doesn't realize that the mouse drops off in middle of transmitting 3 or 4 byte data packet, and as such it gets "out of sync". Or something else hotplug-related. But it's definitely not something you need a CPLD chip to solve. Rio444's ISA card uses an AVR microcontroller to interface the mouse after all.

Anyways, I bought a cheap KVM switch from local second hand marketplace, when it gets here I'll check out what's happening there with a logic analyzer.

They types of KVM people generally use which give these sorts of issues are the "active" ones which emulate a mouse being connected even when switched away.

If the cheap KVM you got is just a passive switch it won't really help