max232 draws a lot together with the mouse it could be too much. But currently it is not my problem. The problem is, that RTS is at -12V and toggles very shortly to +12V and back to -12V in that period I have to initialize the MCU and finalize serial initialization to get the mouse driver to eventually flip the voltage back to 12V again. It's a bit more complicated, than looks like at the first glance. I don't want to tell anything wrong now, but I'm in it and will report as soon as I got more info.

I see. Good luck with that ^^

By the way in the link I sent, that person made a small comparison list with several drivers (including the MAX232) and apparently there's a chip named "1488" that draws less current

Yeah, I know that link, I studied it already carefully as I was investigating on this topic.

Speaking of -12V, would your adapter (or Matze's adapter for that matter) work on a system lacking a -12V rail?

I'm looking for a solution that would work in a Tandy 1000 that would be powered by a PicuPSU, which, as I understand it, cannot provide -12V. This computer lacks integrated serial ports and doesn't use -12V internally by default, but routes the -12V rail to the expansion bus, to be used by expansion cards that have a serial port. So I'm kind of wondering how/if a serial port would work with an adapter like yours in such a system without -12V power available.

Thanks. 🙂

You mixed something. PicoPSU doesn't have -5V, but it has -12V, just as required by ATX standard. If you have serial port in your PC, you also will have -12V by specification.

Thanks for correcting me. Good to know that the PicoPSU will work fine for this. 🙂

Resurrecting this thread to report that the adapter works flawlessly with A4 TECH OP-620D mouse.

appiah4 wrote on 2023-12-20, 07:46:

Resurrecting this thread to report that the adapter works flawlessly with A4 TECH OP-620D mouse.

The cheap one that's also sold on Amazon? Nice touch as it does not even mention PS/2 compatibility anywhere.
I guess you also used the "usual" USB-> PS/2 plug for that to attach it to the adapter?

1541 wrote on 2023-12-20, 08:35:

The cheap one that's also sold on Amazon? Nice touch as it does not even mention PS/2 compatibility anywhere. I guess you also u […]
Show full quote

appiah4 wrote on 2023-12-20, 07:46:

Resurrecting this thread to report that the adapter works flawlessly with A4 TECH OP-620D mouse.

The cheap one that's also sold on Amazon? Nice touch as it does not even mention PS/2 compatibility anywhere.
I guess you also used the "usual" USB-> PS/2 plug for that to attach it to the adapter?
ps2.jpg

Yes and yes to both.

Sorry for the necro... but I can't get the adapter to work with windows 3.1.
What driver should I use?
Adapter is connected to com1 and works in dos with cutemouse driver.

edit:
Oh never mind I can't get any other driver or mouse to work in dos so its my io card that is having a problem.
Real serial mouse logitech and microsoft works with ctmouse driver but not with any other driver. And adapter works with both modes (logitech and microsoft) with ctmouse driver but not with any other driver.

edit2:
Found the problem with my io card... it was configured to com1 address 03F8h but to irq3 and default irq would be irq4.
After changing irq to 4 I got other drivers in dos working and windows works in microsoft mode with real microsoft serial mouse and adapter set to microsoft mode. But windows hangs if I set it to logitech mode and set adapter to logitech mode.

@scorp First of all, I want to thank you for this project, especially because you published it on GitHub.

I’ve been meaning to solder the adapter together for a while now. I decided to solder everything by hand and not use a pre-made PCB. Although I made two small mistakes in my implementation that cost me some time (and nerves), it worked after I fixed them. 😀

The first problem was that I connected pin 11 of the MAX3232 to D5 (RX) of the Arduino instead of pin 12. I found and fixed that relatively quickly.

The second problem took me a bit more time: I only had a male RS232 connector and no female socket on hand. As a result, I misread the pinout and soldered the pins of the MAX3232 to the RS232 connector in reverse order. Fortunately, I had an RS232 female-to-female cable (not a null modem cable), so the connector itself wasn’t an issue. Luckily, the manufacturer of the COM port on my notebook had printed the pin numbers on the socket, so I was able to spot and correct the error. Otherwise, I’d probably still be wondering why it wasn’t working. 😉

Since I have a lot of those faulty RS232-TTL modules:

I removed the chip from one of them, mounted it on an adapter board, and added the appropriate capacitors according to the schematic.

To make the soldering easier, I photographed the underside of my board and numbered the pins according to the schematic:

I then printed this layout and, in three steps, marked the necessary traces (faintly visible in red):

From the top, it doesn’t look too bad. 😉

In contrast to the underside 😒

I’m planning to print a cover for this so it doesn’t look as bad. 😉
(And that's enamel-coated copper wire, not bare copper.)

Overall, this was a great project to work on during the holidays. Thanks again, scorp!

and two more:

This layout was relatively easy to solder, as the inputs and outputs of the respective components are more or less positioned opposite each other. However, the adapter can only be used with some devices if a serial extension cable is used.

What’s really cool is the streaming mode, as it allows me to easily use the adapter with my KVM switch (equip SW 0407 C). 😀 (This is the downside of the serial-PS2 adapters from https://www.serdashop.com/PS2TOSERIAL <- this one doesn’t work with my KVM switch.)

And the first implementation now also has a base plate, which hides the imperfections. 😉

Nice! Thank you for the feedback.