Looking for a Depraz mouse.

Tony Duell ard at p850ug1.demon.co.uk
Mon Sep 24 16:56:25 CDT 2007

> Sorry for late reply...
> Mine were wired as follows:
>      pin       function
>       1        +5V
>       6 (PB0)  Middle button
>       8 (PB1)  Left button
>      10 (PB2)  Right button
>      14 (PB4)  Y1
>      16 (PB5)  Y2
>      18 (PB6)  X1
>      19        GND
>      20 (PB7)  X2
> Whereas the typical pinout for mice on a beeb seems to be one of:
>      pin      Variant A   Variant B
>       1         +5V         +5V
>       2 (CB1)   X1          X1
>       4 (CB2)   Y1          Y1
>       5         GND         GND
>       6 (PB0)   X2          Left
>       8 (PB1)   --          Middle
>      10 (PB2)   Y2          Right
>      12 (PB3)   --          X2
>      14 (PB4)   --          Y2
>      16 (PB5)   Left        --
>      18 (PB6)   Middle      --
>      20 (PB7)   Right       --

Putting one of the X signals and one of the Y signals the CB lines makes 
sense, since IIRC you can generate an interrupt from those lines. Then 
the mouse driver can resposd to that interrupt by seeing which axis 
changed state and what the state of the other signal on that axis is (to 
determine direaction.

IIRC, there's nothing special about lines PB4 or PB5, you can't use them 
as inputs to counters, or the shift register, or as interrupt lines, or.. 
Which seems to indciate that _if_ yuor mouse was designed to plug into a 
Beeb user port, then the drier had to poll the user port often enough to 
detect changes on these lines. Hmmm...


> Yep, mine's the same... I'd originally assumed it was for an ACW (as according 
> to folklore their optional mouse was a P+G) but I'm not sure what the standard 
> mouse port was for an ACW with the mouse board (I've got an ACW here with the 
> mouse board fitted, but with no wiring to any socket on the rear panel) - I 
> should have a look at the service manual and your reverse-engineered data 
> sometime to see if that gives any clues...

Unfortunately my ACW doesn't have  mouse board at all, so my diagrams 
can't cover it. The serivce manual has not real technical info on the 
mouse at all, it's a boardswapper guide for that section (but has 
component-level repair info for the I/O processor (BBC B+ board), 32016 
board and monitor. I thought the mouse interface was an Acorn design, so 
it's odd the schematic isn't included.

I thinkl I read somewhere that the ACW mouse plugs into a DE9 connector 
on the back, which is then linked to the mouse interface PCB, which in 
turn plugs into the 1MHz bus (I think physically it's in the same side 
tray has the hard disk interface boards). I _asusme_ the signals on that 
DE9 are +5V, ground, 2 pairs of quadrature signals and 3 button signals.


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