ps2 to usb mouse

so i got ps2 usb adapter for the 5 button ball(?) mouse i got. but plugging in nothing happens. i think i want to try changing the mouse number as described in risc manual but am afraid of locking myself out if change cmos. so, to edit files i am introducing myself to raspbian. by reading debian manual in like 3 different languages. :-D
-go vegan or something

I deduce (probably incorrectly) that you are trying to plug a PS2 mouse into RISC OS machine that has USB (A pi?).
PS2 to USB adapters are dumb (No electronics). For further info see:
Here and here

As Chris says, there is no simple adaptor that will make a PS/2 device work on USB. You’d need something that speaks both protocols and translates.

However, a lot of the older generation of USB keyboards and mice had a simple plug on thing that told the device to revert to speaking PS/2 instead of USB. It’s the chip inside the device that recognises and switches how it communicates – http://datasheet.digchip.com/456/456-31794-VT5363.pdf

USB has been around long enough now that a device may not have any fallback to PS/2.

There are active adaptors, such as this

also available from your favourite tat bazaar and other places…

I am using one of these on the RPi, for the (ball) mouse. NO problems so far, and I am seriously thinking of ‘borrowing’ the Keyboard from my RPC and plug it in (d**n wrong layout USB keyboard!!)

PS2 to USB adapters are dumb (No electronics).

No they’re not. Some adaptors are dumb, some are active and happily convert most PS/2 mice & keyboards to USB. I’ve been using one ever since the BeagleBoard came out, never mind the Pi.

There are active adaptors, such as this

Some are even sold by Chris here !

For a long time I used a RiscPC keyboard via adapters like these (the ones in Theo’s photo), simply because I loved the RPC keyboard build quality. Still supply them very occasionally for users to use with RISC OS machine (ARMX6 etc) to preserve their old keyboards. Less so mice, because really, PS2 mice are usually pretty horrible after 20 years ;)

I use the one in the photo with my RiscPC keyboard too.
I had a problem with it in that for some reason the usb mouse button did not react correctly (ex: SELECT opened a menu) till I had clicked at least once on all mouse buttons. Then someday I brougth my RPi with me, and when I got back home I reconnected everything and the problem vanished. I think I reconnected them on different ports and that now the usb mouse is seen before the adapter.