Date   : Wed, 15 Aug 2007 09:28:02 +0100
From   : dl.harper@... (David Harper)
Subject: Depraz mice + Master 512

Jules Richardson wrote:

>> Standard mouse pinouts are:
>>
>>     pin               function
>>      1                   5V
>>      2 (CB1)        X Ref
>>      4 (CB2)        Y Ref
>
> Presumably those are still outputs from the mouse to the BBC?

Yes. From the mouse the two X and two Y outputs are of the same kind - they 
are simple on/off signals from two light detectors (for each direction) 
interrupted by spokes on the wheels connected to the rollers.

No processing takes place in the mouse itself. The Beeb uses the signal from 
one X-detector (called X ref) as an interrupt, and the signal from the other 
one (called X Sec) is then used to determine whether the movement is 
leftwards or rightwards; the same with the two Y signals.

>> Once the hardware is correct, you do not need to do anything to get the
>> supplied version of GEM to use the mouse.
>
> Good :)
>
>>     http://www.cowsarenotpurple.co.uk/bbccomputer/master512/software.html
>
> Curious. What was the third floppy in your photo? I've got originals of 
> the
> DOS boot disk and GEM disk; what was the other? (Just ADFS utilities?)

There are 4 disks. (One is in the drive in the photo.) See:
    http://www.cowsarenotpurple.co.uk/bbccomputer/master512/system.html

> And hmm, I still need to find where my user guide's gone...

Don't bother. It is hopeless. Look at the Chris Snee version, along with 
Robin Burton's Technical Guide. Electronic versions on:
    http://www.cowsarenotpurple.co.uk/bbccomputer/master512/bibliography.html

David Harper