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. 🙂