PC mouse adapters (PS/2 <-> RS-232)

PS/2 and serial mouses use diffrent communication protocols and signal levels and they can't be generally used in other interface just by changing the plug. For more technical details take a look at PC mouse hardware document.

Some manufacturers (mostly Logitech and Microsoft) make mouse models which are designed to handle both PS/2 and serial mouse protocols. Those mice come with suitable adaptor to convert the connector to other format.

Mouse which is designed to handle two mouse protocols is built so that some pins which are not used in normal mouse operation are used for handling the other type interface signals. So the The mouse must be DESIGNEDto work with an adaptor to work correctly. The mouse must be used with the adaptor it is DESIGNED to work with. The mouse adapters are not standardized even that you can buy some adapters separately from computer shops. If you just pick up an adapter there is no guarantee that it will work with your mouse.

Technical details of the mouse adapters

PS/2 mouse connector details

6-pin MINI-DIN connector pinout
(when you look to male connector)

        4 u 6
       1  .  2

        3   5

1.      GND
2.      +5V
3.      DATA
4.      CLOCK
5.      Not used
6.      Not used

Logitech PS/2 mouse to 25 pin RS-232 port

PS/2    BD25
1       7
5       2
2      +5V power from adapter regulator
The +5V power is made from RS-232 signal pins TD, DTR and RTS by summing the current available form those pins and the regulatin git to constant +5V source. The adapter could not be easily opened so I was not able to take a look at the electronics inside the adapter.

9 pin RS-232 connector to PS/2 connector from Microsoft Mouse

BD9     PS/2
1       4
5       1
9       3
8       2
This adapter just gives +5V to mouse and routes PS/2 signal from normally unused 9 pin connector pins to the PS/2 connector.