Commodore CAD Pad Project

By Rick Youngman

Updated : Dec. 2, 2007

 

 

 

Intro:

 

Anyone who has ever tried to do any precise artwork on a C=64 can relate to this project.  To put it simply, is nearly impossible, to draw a straight line with a joystick, and making a true 45 degree line, IS impossible.

 

This project actually was completed 15 years ago and used not only for a drawing tool, but also as a game controller.   It is simple, inexpensive, and someone with minimal soldering skills should be able to complete it, with a little effort.

 

Materials:

 

You will need:

 

9 - momentary (normally open) switches

1 – 9 pin DB9 plug (or a chopped off cord from an old joystick)

some wire and solder and stuff like that.

8 – Diodes *

1 – controller case

 

What kind of switches you use, and how you set this project up in a case is up to you.

 

How it works:

 

The position of the cursor at the joystick port is read by simply grounding pins 1-4 and pin 6 (fire button).  I.e. grounding pin 1 makes the cursor (or sprite) move up, and grounding pin 4 makes it move to the right. That is great, in theory, but not precise in practice, because one slip of your hand will trigger another direction, and all you have is a crooked line. Trying to hold a joystick handle to draw a 45 degree line is even worse.

 

So the solution is to mechanically close the contacts by push-buttons, allowing precise control of the cursor’s movement. This project goes one step further,

by allowing you to use ONE button to push TWO !!

 

This is explained better by considering this. If you wanted to move the cursor at 45 degrees to the right, you would have to hold both the right, and up button at the same time.  That works, ONLY – I MEAN ONLY --- you can push both buttons EXACTLY at the same time !!!!!!!!!!!!!!   That’s impossible !!!!

 

Not any longer ….. because we are going to “add” that button !!

 

Look at the picture below and you will understand.

 

The concept is so stupidly simple, I won’t go into the all the nitty gritty here.  For this explanation, we will only look at making a 45 degree angle to the upper right area of the picture.

 

Because of the diode’s inline on switch # 3, they prevent “feedback” between SW 1 and SW 2, so pressing either of those switches allows them to act normally, BUT, by pressing SW 3,  the ground is now latched to the output of BOTH of those switches AT THE SAME TIME, resulting in a perfect 45 degree line !!!

 

Some Suggestions:

 

How you use this project, and or construct it is entirely up to you. It is simple enough to be able to just mount some cheap switches in a box and wire the diode’s point-to-point, or you can make a PC board, if you have the skills.

 

If you want to use this project as a game controller (it works very well for that too) keep in mind what kind of switches you will use, and how much abuse they will handle.

 

How you locate the switches is up to you.

 

or you could even setup the switches like a Playstation pad too.


Full Layout

 

Closing Note:

 

I have started to make a template for you that want to etch your own PC board, but any help there would be welcome, as my time is limited (and the software I use for making etch patterns really sux, and takes boo-koo time !)

 

In the mean time, here is a simple hardware hack, that will be very useful, and can supply a missing link, to something that was never produced.

 

Rick Youngman

Check out my CD’s too, if you get time:

http://users.commspeed.net/wlbbs