Path: utzoo!news-server.csri.toronto.edu!rutgers!cs.utexas.edu!usc!elroy.jpl.nasa.gov!jarthur!nntp-server.caltech.edu!nyet
From: nyet@nntp-server.caltech.edu (prof. n liu)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Looking for Joystick code
Message-ID: <1991Mar12.230926.3458@nntp-server.caltech.edu>
Date: 12 Mar 91 23:09:26 GMT
References: <27795@netcom.COM>
Organization: California Institute of Technology, Pasadena
Lines: 92

resnicks@netcom.COM (Steve Resnick) writes:

>I'm looking for some C (preferably Turbo C) code to access the joystick port.
>What I need is a way to read the current X/Y values and the button status.
>This is going to be part of a PD game, so the code should be PD/royalty free
>to avoid copyright infringements as well as an outlay of cash :)

Just whipped something up real quick (MSC 6.00)
I think its short enough to post here.
Note: this uses dos interrupt 15, and does not read the port... reading the port
for this purpose (i think its address 400-407 or something) is a PAIN!

I tried to read the port using C only and it sucks.. only way to do this is
probably with assembly, since timing is vital. Turns out you have to TIME
how long a certain bit stays high... joystick position is then proportional
to that time.

The interupt calls i did are almost identical to what you need for Turbo C,
i think - the Turbo C bible (Waite Group) documents int86, at least.

The interrupt info for the call itself i found in:

iAPX 86 Interrupt Primer, by Ralf Brown (i got it somewhere by ftp, can't 
remember where), last updated 4/90.

I highly recommend it for doing any type of interrupt programming.

There's really nothing spectacular here, so i doubt i need to copyright it :)

'nother warning: this is by no means robust enough to just slam into any old
code.. its just kinda a guideline. Use at your own risk.

Nye Liu
nyet@cobalt.caltech.edu

Microsoft C 6.00 code follows:
-----cut me here, press n if you don't want to read this:)-----

#include <stdio.h>
#include <conio.h>
#include <dos.h>   /* i think this is msdos.h for TC */

/*  nye's quick 'n dirty joystick program */

/*  uses dos interrupt 15, ah=84h */

/* pass stick = 0 or 1 depending on which joystick you want to read */

void getjoy(int stick, int *button1, int *button2, int *x, int *y)
{
	union REGS in, out; /* pretty sure this is standard */
	int byte;

	in.h.ah =0x84;
	in.x.dx =0x01;
	int86(0x15, &in, &out);    /* probably have to change this for TC */
	if (stick==0)
	{
		*x=(int)(out.x.ax );
		*y=(int)(out.x.bx );
	}
	if (stick==1)
	{
		*x=(int)(out.x.cx );
		*y=(int)(out.x.dx );
	}

	in.x.dx =0x00;
	
	int86(0x15, &in, &out);    /* probably might have to change this too */
	if (stick==0) byte=out.h.al;
	if (stick==1) byte=out.h.bl;
	*button1=*button2=0;
	if ((byte & 16) != 0) 
		*button1=(-1);      /* 0 = button down */

	if ((byte & 32) != 0) 
		*button2=(-1);
}
		
		
main()
{
	int x,y,b1,b2;

	while(!kbhit())
	{
		getjoy(0,&b1,&b2,&x,&y);  /* status of joystick 0 */
		printf("%d %d %d %d \r",b1,b2,x,y);
	}
}