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From: simpson@aplcen.apl.jhu.edu (Simpson David Grant)
Newsgroups: comp.sys.ibm.pc.misc
Subject: <None>
Summary: Joysticks on the PC - Summary
Keywords: Joystick
Message-ID: <1991Feb8.050138.2590@aplcen.apl.jhu.edu>
Date: 8 Feb 91 05:01:38 GMT
Reply-To: simpson@aplcen (Simpson David Grant)
Organization: Johns Hopkins University
Lines: 30


My thanks to those who answered my recent question on how to
program the game port for a joystick on my PC clone (Zeos 386).
(Special thanks to Rolf Michelsen for particularly helpful
information.)  My problem was that the BIOS "Read Joystick"
function on my 386 (BIOS interrupt 15h, function 84h) would
correctly read the joystick "fire" buttons, but not the joystick
positions.  The joystick position information returned by this
interrupt was just randomly changing "garbage".
  As Mr. Michelsen has pointed out, the problem is most likely
due to my cloned joystick card not being recognized by the
boot-up routine.  The solution is to read the joystick information
directly from the I/O ports (I/O port address 201h) with an
assembly language routine via the IN and OUT instructions.
The "fire" button status may be read directly from this port,
but the position information must be calculated by using the
timer chips available on the PC motherboard.  A routine for
doing this is available in the book "The IBM PC from the Inside
Out" by Sargent and Shoemaker (Addison-Wesley, 1986 (revised
editon), pp. 139 - 140).
  I am working on a TSR to intercept BIOS interrupt 15h and
replace function 84h with this routine in order to allow
joystick programs to work properly.  I can post the assembly
language source here when it's done (if it is a short program
and there's sufficient interest), or I could e-mail individual
copies to anyone interested. (Or I could put in on "Anonymous
FPT", if someone can tell me just what exactly "Anomymous FPT" is.)
  Thanks again for everyone's help!
                               
                                    David Simpson