Re: TI-H: Joystick connector

To: ti-hardware@lists.ticalc.org
Subject: Re: TI-H: Joystick connector
From: "Osma Suominen" <ozone@clinet.fi>
Date: 12 Feb 1998 14:46:09 -0000
In-Reply-To: <01bd3766$7015a320$b92cf3cd@robert>
Reply-To: ti-hardware@lists.ticalc.org

Robert Brack wrote:

> I got a huge brainstorm in the middle of band the other day.  Since we weren't
> playing, I got out a pad and started scribbling out an experimental schematic. 
> This is still preliminary, but I figured out a way to interface a joystick to
> my calc (gamepads will be done a little differently).  The first thing I did
> when I got home was pull apart my joystick and use my DMM to measure voltage on
> everything.  I then fixed my schematic.  I haven't built it yet, but I'd like
> some feed-back.  This should work with and game currently out.  I will be
> posting a finished schematic at ticalc.org within two weeks.  Tell me what you
> think.

Some time ago, I thought about interfacing a joystick to the calc with an
I2C system. A digital (Amiga, Atari, C64 style) joystick would be connected
to the PCF8574 I/O expander, which in turn would be connected to the link
port or SPinTerface port. The rest would just require some programming.

I thought about an interrupt driven system where an interrupt routine polls
the joystick port constantly, and hands over this information to the
application. It might even be possible to make the joystick movements look
like keypresses to the running game, but this is unlikely because I assume
most games read the keypad directly and not via ROM calls. Making those
games work with the joystick would require tinkering with the internals of
the TI.

Of course, the system would also work fine without even using interrupts. A
game could have direct joystick support, and poll the interface chip
whenever it wants. The programming should be a piece of cake with my MBus
routines, and the hardware isn't difficult to do either. I just don't know
if there's real need for a big clumsy joystick to be connected to a small
and handy calculator, but there are some people who will want it anyway.

How have you dreamt up the hardware part? Does your system connect to
analog (PC,15pin) or digital(9pin) joysticks? The TI community ain't big
enough for both of the systems, but if you want, you can do all the stuff
yourself and I won't start making a rival system. I'm too busy even without
the extra work.

-Ozone

-- 
*** Osma Suominen *** ozone@clinet.fi *** http://www.clinet.fi/~ozone ***

References:

TI-H: Joystick connector

From: "Robert Brack" <reb@netride.com>