Path: chuka.playstation.co.uk!scea!peter_alau@playstation.sony.com
From: Michael Briere <mikey@accessv.com>
Newsgroups: scea.yaroze.beginners
Subject: Re: JOYSTICK FUNCTION
Date: Fri, 17 Jul 1998 18:57:40 -0400
Organization: SCEA News Server
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Hi Elliott! Thanks for your help! I really like your joystick lib as it does
include the diagonal combinations. I also like your suggestion of using
printfs to see the math behind this. I am confused though about what you've
put in your reply to me and what you have in your padstuff.h header file.

In your reply you say that controller 1 uses bits 16 to 31 and controller 2
uses bits 0 to 15, yet in your header file when you assign buttons to bits
it's the reverse. Am I missing something here? I know I have to do some more
reading on bitwise operators to get all of this, so I wouldn't be surprised
if I'm the one who's getting it wrong. I've got to take a good look at your
padstuff now. Thank you!

Elliott Lee wrote:

> First of all, you might want to try my pad routine library (other people
> have also written some good ones) instead of using the book's, but it
> works similar:
>
>         http://www.scea.sony.com/net/yaroze/pages/ftp/elee2/padstuff.zip
>
> (This corrects a #define error in the pad.h file.)
>
> Anyways, what happens is that every frame the controller is polled and
> the status stored in a fixed location in memory.  The PadRead() just
> references that area.  But what it returns is a 32-bit integer which
> looks like this:
>
>         bits:    31 .. 16          15..0
>         use:    Controller1     Controller2
>
> The PadRead() just takes the relevant 2 bytes from the 2 controller
> pad status buffers and returns it to you in a form which you can then
> do bit testing on.
>
> If you want to see what I mean in real-time, you can do what I first
> did: make a simple program that just spits out the bit values to the
> screen or to STDOUT (via printf()).
>
> So, the defines you see in the Sony demo's pad.h are for controller 1.
> To get the bits for controller 2, just shift the mask over 16 bits to
> the left.
>
> Confused?  Did this help?
>
> Michael Briere wrote:
> >
> > Hi! I need some explanation on how the joystick function u_long
> > PadRead(void) works.
> > Here's the complete function:
> >
> > u_long PadRead(void)
> > {
> >     return(~(*(bb0+3) | *(bb0+2) <<8 | *(bb1 +3) << 16 | *(bb1+2)
> > <<24));
> > }
> >
> > I understand that this reads the joystick and returns a value equal to
> > the button that was pressed as shown in the yellow manual. However I'd
> > love it if someone could show me the math behind this with an example.
> > ie. if PADLstart (bit 11) is pressed on joystick #1 which should be put
> > in the *bb0 pointer. I could spend hours trying to figure this out for
> > myself, but I'd really appreciate your help. I know the function works,
> > but I make it a habit of understanding the code I use in my programs.
> > Thanks!
>
> --
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