There are few different incompatible standards of bus mice. Basically the bus mouse is raw mouse signals going to an ISA card where processing of the raw signals is done and then exposed to computer is some way. PS/2 and COM port mice essentially have most of that ISA card inside them.
Making your own is a bit complicated because of these reasons.

Anonymous Coward wrote on 2022-10-05, 15:56:

It seems the serial converters are kind of bandwidth starved, which becomes an issue over 640x480.

what would serial speed have to do with mouse precision (dpi)?

Anonymous Coward wrote on 2022-10-05, 15:56:

The whole point of the bus mouse was that it provided a lot more resolution

afaik the whole point was cost, omitting microcontroller and using 8255 with lots of irqs burning cpu time. Same reason (cost) amiga/atari ST used raw encoder signal mice.

what would serial speed have to do with mouse precision (dpi)?

This one seems self-evident.

afaik the whole point was cost, omitting microcontroller and using 8255 with lots of irqs burning cpu time. Same reason (cost) amiga/atari ST used raw encoder signal mice.

The bus mouse predates PS/2.

Anonymous Coward wrote on 2022-10-07, 00:16:

what would serial speed have to do with mouse precision (dpi)?

This one seems self-evident.

in the same way Trabant was a proof composites had no future in cars

Anonymous Coward wrote on 2022-10-07, 00:16:

The bus mouse predates PS/2.

and serial mice predate bus ones

Maybe this thing can be reversed ?
Bus mouse adapter for PS2 computers... = opposite direction, but.... ?
https://www.flickr.com/photos/andysretrocompu … in/photostream/

Or maybe it actuall works in both directions already ?
(guess not, as both ends of the adapter block has a identical looking bus/in-port connector)

PS: more pictures here (not mine!):
https://www.ebay.com/itm/234556099514
There also exists PS2 adapter cables as well as DB25 serial ones, that will all fit into that rectangular adapter, not only that DB9 serial.

I have that card and adapter. There are different dongles that plug into the white box. I believe there are dongles for PS/2 and Serial. You wouldn't happen to own the manual, would you?
I think it was designed to allow the inport mouse to work in serial and PS/2 ports. I'm not sure if it's bi-directional. I haven't touched mine in quite a few years, and some of my cables are frayed. I'd like to know more about it. I think at one time I tried to plug a Leaguer bus mouse into a PS/2 port using this adapter but it didn't work. As Tiido said, not all bus mice (mouses?) were made to the same standard, so that might explain the reason.

If anyone needed to eyeball a Logitech card to campare, I posted one here... A pic to show the grandchildren, Logitech Bus Mouse and Card Together!&

I looked up that PMIC chip around then and some supplier claimed to be sitting on a few hundred, enough for hobby scale projects I guess, but not for "real" production.

bestemor wrote on 2022-10-07, 20:53:

BusMouse2PS2adapter.JPG

Afaik this is the part Microsoft cheapened out of in their mice - microcontroller interpreting raw encoder signals send by the inport mouse and outputting serial/ps2

Has anyone ever opened the little white box?

Anonymous Coward wrote on 2022-10-08, 00:26:

... You wouldn't happen to own the manual, would you? ...

You can find some manuals here:
https://minuszerodegrees.net/msmouse/Microsoft%20mouse.htm

Ha! Great find!

Anonymous Coward wrote on 2022-10-05, 15:56:

has anyone yet attempted converting a bus mouse port to work with a ps/2 mouse?
…
Are bus mouse controllers hard to come by, or is it possible to build them from scratch?

I know it's a late reply, but I just made one of these for myself (That's a blog post where I talk more in depth about it).
It's pretty easy to make one if you are handy soldering, actually. Any PS/2 ball mouse (and many early optical ones) expose quadrature signals internally. early optical sensors did this to be able to use the same PS/2 and USB controller chips that ball mouses did. Ball mouses need to because the signals on a bus mouse port are actually exactly the same as the raw outputs from the phototransistor sensors on the encoders internally.

You'll need a sacrificial mouse to make it work. I bought an old $10 PS/2 (and RS-232) hybrid mouse off of ebay, a Belkin F82E01. But Any PS/2 (or PS/2 and RS-232 combo) mouse will work. Using a continuity tester, I figured out which traces from the phototransistors on the mouse were being connected to the PS/2 controller chip, which in my case was an HMC HM8450. I then desoldered the phototransistors and hooked the Xa/Xb and Ya/Yb pins of a bus mouse connector to the correct traces. I used a 9 pin D-sub (DE9) connector because I have PC-98 computers and many of those used one of those instead of 9 pin mini DIN, and I have an adapter from 9-pin mini DIN to DE9 for my PC-98's.

If you wire up Xa and Xb or Ya and Yb backwards, moving one direction will make the mouse pointer move the opposite direction. So just swap the two wires if that happens.
Also with my particular mouse controller chip that I used, it expected buttons to be brought to 5 volts when clicked (active high), but my bus mouse outputted grounded when clicked (active low). So I added a 74LS04 inverter chip and inverted the three mouse button inputs before I fed them to the signal pins on the donor mouse's circuit board.
Later I went back and added a 22 kilo-ohm resistor tied between 5V and each of the unused inputs on the inverter chip just so that it'd still work correctly if I swapped the 74LS04 for a CMOS version or a regular 7404.

Then I made a housing, and plugged it into a PS/2 to USB adapter just to try to avoid killing my PS/2 port if I messed up. it works great. I've used it to play DOS Doom and Daggerfall on my 90's Gateway PC with one of my bus mouses, and I'm using that same bus mouse to write this post right now.

LMK if anything's confusing that I said. But basically you can hijack the existing circuitry of any PS/2 or RS232 mouse to adapt a bus mouse.

I gotta head to work now (gonna be a bit late, oh well). Hope this helps someone though.