clq@littlei.UUCP (clq) (03/23/88)
Does anyone have any information on how to read/use the game port on an IBM/PC-AT??? I would perfer "C" routines, but can use ASM routines if necessary. Pointers to books, source or anything would be helpful. Thanks Carlos Qualls Intel Corp. 5200 N. E. Elam Young Parkway Hillsboro, Oregon 97123 Office (503) 696-5491 USENET: tektronix!reed!littlei!clq
ajmyrvold@violet.waterloo.edu (Alan Myrvold) (03/24/88)
How to read the joystick on an IBM PC.
This program, written for Turbo C, version 1.0 shows how
the joystick postion may be read.
I am indebted to uunet!netxcom!jallen (John Allen) for answering
my previous posting on the subject and providing technical
assistance. Text from his EMAIL to me is included in the program.
-------------------------------------------------------------------
Si je t'aime? Bien sur que je t'aime! Ne suis-je pas en train de
te le prouver encore une fois, dans ce lit?
-------------------------------------------------------------------
Alan Myrvold ajmyrvold@violet.waterloo.edu
-------------------------------------------------------------------
----------------------------- JOY.C ----------------------------
/* Demonstration of reading joy stick postition
Written March 24, 1988
Written by : ajmyrvold@violet.waterloo.edu (Alan J. Myrvold)
Technical assistance from : uunet!netxcom!jallen (John Allen)
Turbo C Version 1.0
*/
#include <stdio.h>
#include <dos.h>
#include <bios.h>
typedef struct {
int sw1,sw2;
int x,y;
int cenx,ceny;
} joy_stick;
joy_stick joy;
#define keypressed (bioskey(1) != 0)
#define kb_clear() while keypressed bioskey(0);
void GotoXY(int x,int y)
{
union REGS r;
/* Set XY position */
r.h.ah = 2;
r.h.bh = 0; /* Assume Video Page 0 */
r.h.dh = (char) y;
r.h.dl = (char) x;
int86(16,&r,&r);
}
void ClrScr()
{
union REGS r;
/* Get video mode */
r.h.ah = 15;
int86(16,&r,&r);
/* Set video mode */
r.h.ah = 0;
int86(16,&r,&r);
}
/*
From: uunet!netxcom!jallen (John Allen)
1. Trigger the joystick oneshots with an 'out' to 0x201.
This will set all of the joystick bits on.
2. Read (in) 0x201, finding:
Bit Contents
0 Joystick A X coordinate
1 Joystick A Y coordinate
2 Joystick B X coordinate
3 Joystick B Y coordinate
4 Button A 1
5 Button A 2
6 Button B 1
7 Button B 2
3. Continue reading 0x201 until all oneshots return to zero,
recording the loop during which each bit falls to zero.
The duration of the pulse from each oneshot may be used to
determine the resistive load (from 0 to 100K) from each
Joystick, as: Time = 24.2msec. + .011 (r) msec.
4. To do this correctly, I recommend calibrating the joystick;
have the user move the stick to each corner, then center it,
while recording the resulting values.
*/
void disp_stick(int line,joy_stick *joy)
{
GotoXY(0,line);
printf("sw1 %d sw2 %d",joy -> sw1,joy -> sw2);
GotoXY(0,line+1);
printf("x %4d y %4d",joy -> x,joy -> y);
}
void read_stick(int stick,joy_stick *joy)
{
int k,jx,jy;
int c,m1,m2,m3,m4,m5;
/* Define masks for the chosen joystick */
if (stick == 1) m4 = 1; else
if (stick == 2) m4 = 4; else
printf("Invalid stick %d\n",stick);
m5 = m4 << 1;
m1 = m4 << 4;
m2 = m5 << 4;
m3 = m4 + m5;
/* Trigger joystick */
outportb(0x201,0xff);
c = inportb(0x201);
/* Read switch settings */
joy -> sw1 = (c & m1) == 0;
joy -> sw2 = (c & m2) == 0;
/* Get X and Y positions */
for (k = 0; (c & m3) != 0; k++) {
if ((c & m4) != 0) jx = k;
if ((c & m5) != 0) jy = k;
c = inportb(0x201);
}
joy -> x = jx - (joy -> cenx);
joy -> y = jy - (joy -> ceny);
}
int choose_stick(joy_stick *joy)
{
int init_swa,init_swb,swa,swb;
int c,retval;
printf("Center joystick and press fire, or press any key\n");
kb_clear();
outportb(0x201,0xff);
c = inportb(0x201);
init_swa = c & 0x30;
init_swb = c & 0xc0;
do {
outportb(0x201,0xff);
c = inportb(0x201);
swa = c & 0x30;
swb = c & 0xc0;
} while ((swa == init_swa) && (swb == init_swb) && !keypressed);
if (swa != init_swa) {
printf("Joystick 1 selected\n");
retval = 1;
} else if (swb != init_swb) {
printf("Joystick 2 selected\n");
retval = 2;
} else {
printf("Keyboard selected\n");
kb_clear();
retval = 0;
}
if (retval != 0) { /* Determine Center */
joy -> cenx = joy -> ceny = 0;
read_stick(retval,joy);
joy -> cenx = joy -> x;
joy -> ceny = joy -> y;
}
return(retval);
}
main()
{
int k;
k = choose_stick(&joy);
ClrScr();
if (k != 0) while (!keypressed) {
read_stick(k,&joy);
disp_stick(0,&joy);
}
}