I approve of this , I really liked the idea from the beginning 😀

Love it, however the number of slots in my system is getting fewer all the time. What is the PLCC chip? Some Atmel MCU? Does it do the UART and PS/2 translation?

root42 wrote:

Love it, however the number of slots in my system is getting fewer all the time. What is the PLCC chip? Some Atmel MCU? Does it do the UART and PS/2 translation?

The PLCC chip is a classic 16c550 UART, a lot of users here, I'm sure, remember it in its DIP-40 package. Isa i/o cards usally have one or more on them.

Isa Serial with two 16c550 DIP-40 ICs:

The AVR MCU is the dip-20 on the right (IC3 on the rendered board), since UART and MCU are on the same board no RS-232 Driver ICs are needed and they directly communicate at TTL-232 level.

That's a great project, I had to hunt down a NOS serial mouse which, being a ball one, is not exatly great by today's standards. Still more comfortable than my first 3-button Genius.

But I have to ask, wouldn't it be easier to put a 5V Cortex-M on that PCB, connect it directly to both ISA and PS/2 port, and then write a custom mouse driver based on CTMOUSE sources? Are there any games or programs that talk directly to the mouse and bypass int 33h? I can't remember any. And a 48MHz Cortex-M should be able to handle ISA bus at full speed with interrupts alone. Literally one chip solution. If not, a small PAL/GAL would just assert WAIT until the MCU can process the read/write.

For even bigger project why not use Cortex-M4 at 120MHz with USB host, that would require voltage translation at ISA but the possibilities...

Deunan wrote:

That's a great project, I had to hunt down a NOS serial mouse which, being a ball one, is not exatly great by today's standards. Still more comfortable than my first 3-button Genius.

But I have to ask, wouldn't it be easier to put a 5V Cortex-M on that PCB, connect it directly to both ISA and PS/2 port, and then write a custom mouse driver based on CTMOUSE sources? Are there any games or programs that talk directly to the mouse and bypass int 33h? I can't remember any. And a 48MHz Cortex-M should be able to handle ISA bus at full speed with interrupts alone. Literally one chip solution. If not, a small PAL/GAL would just assert WAIT until the MCU can process the read/write.

For even bigger project why not use Cortex-M4 at 120MHz with USB host, that would require voltage translation at ISA but the possibilities...

That's another approach and probably it would be a great solution, but it was much easier for me to simply take the already working matze79 adapter and the most used/compatible uart ISA interface on the planet and to combine them in one single board. Matze79 and Felmar Loyd have recently released their new firmware version 1.1 for the ATTiny2313 which adds support for wheel mouse, they have already written the dos and wfw3.11 drivers and utility. Basically I tried to build something simple and very compatible, this kind of serial interface is standard since XT, in this way the project is already finished and working fine in all initial tests. Any change in the firmware, like the uart/MCU communication baud rate is already supported and future updates could be easily implemented simply reflashing the MCU.
Basically I'm a lazy guy. 🤣

You could probably even add another UART for a second, standard RS232 port, saving a slot on ancient machines...

root42 wrote:

You could probably even add another UART for a second, standard RS232 port, saving a slot on ancient machines...

A 16552 Dual UART variant which support 2 serial ports in a single IC can be used in the design: 1 for the adapter and 1 could be used as a standard Serial port, but I don't think it's very common nowdays to use a serial port in retro builds if not for the mouse, unless you are using a 3com sportster modem to show off. 😉 So if you are going to use this board for the mouse you don't need a serial i/o card anymore.

Serial ports are great!

It's fun to play around with (emulated) modems over serial port and link computers with null-modem cables...

GigAHerZ wrote:

Serial ports are great!

It's fun to play around with (emulated) modems over serial port and link computers with null-modem cables...

Playing Doom multiplayer mode, that's nice indeed 😀 well then the second port is a suggestion to consider, thanks.

Great idea. I'd be happy to help too - my love of old computers does not extend to old pointing devices, and whereas I can get my preferred trackballs down to PS/2, they don't talk native serial. Also, PS/2 plays nice with my KVM-switch. All in all lots of PS/2 things I could plug into it to check behaviour. Also have boards down to 8086 to stick them into.

There are lots of serial devices apart from modems and mice. Stuff like Wacom pads come to mind or vintage handheld devices from Palm or Casio. Probably there is lots more.

Great idea!
I suppose that 486 systems never lack COM ports, since they come with the IDE interface, either on the motherboard or on a card. But in certain builds or test setups this may be more tidy and easier to install.

Don't you think a green or gold PCB would match a little better with these old motherboards? Or is the white PCB some prototype stage consideration?

I also agree an extra port on this particular card would be a waste somewhat , allow me to explain
a. XT situation: either onboard ports or the user has installed one of these floppy/serial/lpt cards which are the most common
b. AT situation: same as above, either onboard ports or a 16bit I/O card that already has serial ports

I just don't see a more complex design to include a 2nd serial port getting much use... XT systems for example have 8 ISA slots and OEM ones have onboard ones so I don't think the slot count will be an issue?

Also yes, one can port all that to an arm core and re-invent the wheel in some sense, it just does not worth the time investment IMHO

root42 wrote:

There are lots of serial devices apart from modems and mice. Stuff like Wacom pads come to mind or vintage handheld devices from Palm or Casio. Probably there is lots more.

That's true, I must admit I didn't consider them in retro builds, but it's still a possibility and someone might be interested.

gerwin wrote:

Great idea!
I suppose that 486 systems never lack COM ports, since they come with the IDE interface, either on the motherboard or on a card. But in certain builds or test setups this may be more tidy and easier to install.

Don't you think a green or gold PCB would match a little better with these old motherboards? Or is the white PCB some prototype stage consideration?

You can always use COM3/COM4 settings and still install this card in a late 486 PCI with serial I/O already onboard and active without any conflicts. I can also redesign it with 1 serial port, 1 parallel port and 1 PS/2 port, in this way it can replace any ISA I/O card that we usually install in our builds, but the board will be more expensive and I'm here to decide with you if it's really necessary. For the color I would really like to use the classic brown/copper. I really like it, but I am open to suggestions.

Maybe just offer two boards? One with only one, the other with two ports? Of course the best card would be multi IO with serial, PS/2, floppy, HD XT IDE and maybe even a parallel port on a breakout. 😉

root42 wrote:

Maybe just offer two boards? One with only one, the other with two ports? Of course the best card would be multi IO with serial, PS/2, floppy, HD XT IDE and maybe even a parallel port on a breakout. 😉

The best I can do without big problems is: floppy+1x parallel+1x serial+1x ps/2 but at that point maybe it's better a standard I/O board with the matze79 adapter by itself mounted on the 3d printed bracket. I thought it could be useful to keep it simple, just for those who want ps/2 mouse on old motherboards without it.

Madowax wrote:

You can always use COM3/COM4 settings and still install this card in a late 486 PCI with serial I/O already onboard and active without any conflicts. I can also redesign it with 1 serial port, 1 parallel port and 1 PS/2 port, in this way it can replace any ISA I/O card that we usually install in our builds, but the board will be more expensive and I'm here to decide with you if it's really necessary. For the color I would really like to use the classic brown/copper. I really like it, but I am open to suggestions.

What I wrote was with the background of having a non-PS2 port 486, and the original PS2-mouse-adapter and also your new ISA card at hand. Both PS2 adapters achieve their primary purpose just fine, so that is a luxury decision. But not an easy decision.
The original adapter has the advantage of communicating with an existing com port, though in older systems lacking com ports this may very well be a disadvantage.
The ISA card has the advantage of connecting to the ISA slot: It takes power from there, and it is also automatically fixated in your PC case.
Personally I have no desire for additional COM/LPT ports in a 486 system. The three VLB/ISA IDE Cards I have here all have the usual 2xCOM/1xLPT integrated. Often I disable LPT1 to free IRQ 7 for sound. (But let me not spoil the party for people with even older systems, or for people with one of these interesting dreamblaster LPT sound devices.)

Classic brown/copper PCB, that sounds good.

gerwin wrote:

What I wrote was with the background of having a non-PS2 port 486, and the original PS2-mouse-adapter and also your new ISA card […]
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What I wrote was with the background of having a non-PS2 port 486, and the original PS2-mouse-adapter and also your new ISA card at hand. Both PS2 adapters achieve their primary purpose just fine, so that is a luxury decision. But not an easy decision.
The original adapter has the advantage of communicating with an existing com port, though in older systems lacking com ports this may very well be a disadvantage.
The ISA card has the advantage of connecting to the ISA slot: It takes power from there, and it is also automatically fixated in your PC case.
Personally I have no desire for additional COM/LPT ports in a 486 system. The three VLB/ISA IDE Cards I have here all have the usual 2xCOM/1xLPT integrated. Often I disable LPT1 to free IRQ 7 for sound. (But let me not spoil the party for people with even older systems, or for people with one of these interesting dreamblaster LPT sound devices.)

Classic brown/copper PCB, that sounds good.

Indeed you are right, my board doesn't want to replace matze79 adapter, in a late PCI 486 with integrated I/O and using a floppy Molex for power it up, It would be just perfect. It connects to the serial header of one of the onboard serial and you are good to go, no ISA slot consumed. I designed this board for 8086/286/386/early 486. In these systems you usually got a lot of ISA slots and the need of at least 1 serial I/o card for a mice. I must confess I based this project on my usual EISA/ISA/VLB retro builds:
1x Graphics card
1x Sound card
1x midi card (optional)
1x aha-1542 / buslogic VLB SCSI / aha-2742w eisa (floppy+SCSI HDD)
1x ISA serial to ps/2 mouse
1x Nic (optional)
4, 5 or 6 ISA slots in total.
Done!
But that's my opinion of course, I really like to collect yours. 😀

Why not to keep it really simple? Having a PS/2 port + another COM port just because it can be had almost for free? (As there are dual serial controllers around) Other stuff needs additional chips and make it more complicated... no need for than with this nice little 8bit card.