Date   : Tue, 24 Aug 1999 01:00:20 +0100
From   : Stuart William McConnachie <stuart@...>
Subject: Re: Mouse on the BBC

In message <49363B1E5D%Iain@...>, Iain Williamson
<Iain@...> writes
>> Does any of you guys know how to connect a standard PC-mouse to the
>> user-port in order to use the AMX-software?? (if at all possible?)
>
>The AMX mouse connected to the user port? That's strange; I would have
>assumed it'd be an old-fashioned quadrature mouse, and be connected to
>the analogue port. If that's the case, you can only get quadrature
>signals out of a PS2 mouse (PC mouse) by using a special box like PS2Mouse
>from Stuart Tyrrell; it's not that easy to do.
>
>On the other hand if it plugs into the user port, it must have been a
>digital device; perhaps similar to a modern PS2 mouse.
Although digital in nature, the AMX mouse was a very low level device,
only signalling the BBC with an interrupt when the mouse moved (one
unit) and the direction it moved in.  It was the responsibility of the
BBC to count the number of movements in each direction and thus the
total distance travelled.  I believe the PC mouse interface is much more
complicated, with the PC mouse being a more intelligent, programmable,
device with a serial interface.  

However, thinking about it, with a little work it might just be possible
to hack apart a PC mouse to provide the necessary signals for a BBC.  Of
course it would then be useless for connecting to a PC, but a fairly
cheep option considering the price of a PC mouse and the unavailability
of BBC mice (at which point Chris R. will probably tell me he's got a
thousand in his loft, in which case please would you send me one!)

Has anyone got an AMX mouse they could take apart and draw me a basic
circuit diagram, and tell me how the optical choppers are connected?
Has anyone attempted this before?

Regards,
-- 
Stuart McConnachie (stuart@...              )
43 The Hollows, Long Eaton, Nottingham, NG10 2ES, UK
Mobile: 0966 224307