Date   : Tue, 24 Aug 1999 21:24:51 +0100
From   : Iain Williamson <Iain@...>
Subject: Re: Mouse on the BBC

In message <1EowVaAUCew3EwDX@...>
          Stuart William McConnachie <stuart@...> wrote:

> 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?)
> >
[snip - AMX mouse]
> >
> >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.

I believe the PS2 interface is similar; it sends simple framed serial data
to the computer consisting of change in X, change in Y, button state (not
neccessarily in that order). I can't remember if it does this constantly,
or only when moved.
> 
> 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.

I wouldn't discount the possibility of making your own interface box; a
chip to read the data from the mouse should be available off the shelf,
and the other half should be the same as in an AMX mouse (i.e. the same
bits you'd have to shove into a PC mouse under your scheme). You'd
have to then interface those two bits. A similar amount of work, and a
far neater solution, in all probability.

-- 
  /""\          Iain Williamson
 C  oo      Computer systems engineer 
 _(  ^)
/    ~\