Atari CX70 User manual

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LIGHT PEN
OPERATOR'S MANUAL
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ATARI®
A Warner Communications Company 0
Model CX70
Use with
ATARI® 400™ or ATARI 800™
PERSONAL COMPUTER SYSTEMS
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ATARI
Light Pen
Operator's Manual
COPYRIGHT 1981 ATARI, Inc.
Every effort has been made to ensure that this manual
accurately documents this product of the ATARI Computer
Division. Houiever, because of the ongoing improvement and
update of the computer software and hardware, ATARI, INC.
cannot guarantee the accuracy of printed material after the
date of publication and cannot accept responsibility for
errors or omissions.
C016g67, Rev. 1

ATARI Light Pen Operator's Manual
^QNTgNTS
1. INTRODUCTION
2. POSSIBLE USES OF THE LIGHT PEN
3. CONNECTING THE LIGHT PEN
4. ATARI LIGHT PEN DEMONSTRATION PROGRAM CASSETTE
Loading Instructions
BK Version of PALLET: A Light Pen Painting Program
16K Version of PALLET
5. PROGRAMMING EXAMPLE 1: Using the Light Pen with ATARI BASIC
How Programming Example 1 Works
Experimenting with Programming Example 1
6. PROGRAMMING EXAMPLE 2
7. PROGRAMMING EXAMPLE 3
8. PROGRAMMING EXAMPLE 4
9. PERIODIC MAINTENANCE
Using PENBUF - A Light Pen Utility Program
A Keyboard Substitute
A Teaching Aid
APPENDICES
A. BASICS OF LIGHT PEN OPERATION
B. ATARI LIGHT PEN CHARACTERISTICS
C. TROUBLESHOOTING: What to Do If Your ATARI Light Pen Does Not
Respond as Expected
D. PENBUF FLOW CHART
E. PENBUF ASSEMBLY LANGUAGE LISTING
F. DESCRIPTION OF PENBUF OPERATION
G. NOTES ON MEMORY CONSERVATION/PENBUF MEMORY USAGE
H. GENERAL PROGRAMMING NOTES

ATARI Light P«n Operator's Manual
ILLUSTRATIONS
Figure Page
1 Sample Menu 3
2 Television Screen Display for 8K PALLET Program 9
3 8K Version of PALLET Program Listing 11
4 Television Screen Display for 16K PALLET 13
5 Flowchart for 16K PALLET 19
6 16K Version of PALLET Program Listing 21
7 Color Mode Numbers 23
8 Programming Example 1: Using the Light Pen with ATARI BASIC 29
9 Television Screen Display for Programming Example 1 30
10 PENBUF Loader 33
11 Programming Example 2: Using PENBUF 34
12 Programming Example 2: Modified to Run in Graphics 0 35
13 Television Screen Display for Programming Example 2 36
14 Programming Example 3: A Keyboard Substitute 37
15 Television Screen Display for Programming Example 3 38
16 Programming Example 4: A Teaching Aid 39
17 Television Screen Display for Programming Example 4 40
A. 1 Television Screen Simulation 45
A.2 Television Screen Plus Light Pen 46
D. 1 PENBUF Flow Chart 53
F. 1 Typical Insert-Sort ' 59
G. 1 PENBUF Memory Usage 62

ATARI Light Pen Operator's Manual
SECTION 1 - INTRODUCTION
The ATARI Light Pen is particularly suitable as an educational and
game playing tool as it allows the user to interact directly with the
computer. By pointing to an item on the screeni you can say "There's
the game piece I want to move<" and "There^s where I want to move it."
The most common usei howeveri is to select an item from a list or
menu> as in a multiple-choice test.
Section 2 of this manual describes menu selection and other more
sophisticated uses of the light pen. Sections 3 and 4 give
instructions for connecting the light pen to the computer and loading
the programs on the demonstration cassette. In Sections 5 through 8>
you will find several more demonstration programs to help you
understand how to write BASIC programs using the pen for your own
purposes. These examples will lead you to invent many ways to use the
light pen in your programs. In these examples* we assume you have a
working knowledge of ATARI BASIC as defined in the ATARI BASIC
Reference Manual. Although the demonstration cassette programs and all
of the programming examples in this manual are in BASIC* you may use
the pen with any of the ATARI programming languages.
General programming notes* showing the basic rules for the use of the
light pen are provided in Appendix H. Read through the manual
thoroughly first to acquaint yourself with the operating principles of
the pen. In Section 9* you will find details of the care necessary to
maintain the pen in its best operating condition.
Introduction - 1

ATARI Light Pen Operator's Manual
Introduction -> 2

ATARI Light Pen Operator's Manual
SECTION 2 - POSSIBLE USES OF THE LIGHT PEN
Menu selectionf which is a common use for the ATARI Light Pen> may
take many different forms. One form of light pen selection is
illustrated by the Keyboard Substitute programi provided as
Programming Example 3 (see Section 7). In this program^ the pen is
used to select the letter to be typed on the screen. Programming
Example 4« the Teaching Aid Program< uses the pen in two different
menus. The demonstration program provided on the cassette uses the
pen as a menu selector as well as a graphics tool.
By using the ATARI Light Pen with programs you have written^ you can
form a picturei a plot« a set of letters or groups of instructions on
the television screen. With the pen« you can point to one of those
items on the screen. The computer will read signals coming from the
pen and can interpret those signals so that it knows what action to
take next. As an example> you can produce a list of the different
progams you have available on the diskette in your ATARI Disk Drive.
The list (or menu) might appear as shown in Figure 1.
SJCt RTREK
CHECKBOOK BOEONCER
CHEC KER5
DUNGEONS OND DROGONS
PLOCE THE POINT OE THE LIGHT PEN
OGOINST THE BOH TO EOOD THE PROGROM
Figure 1 - Sample Menu
When you follow the instruction at the bottom of the television
screeni your program will sense that the switch in the tip of the
light pen is pressed and will call the light pen subroutine.
The pen can also serve as a teaching device when a student uses it
to select the correct answer from a multiple-choice set of answers
placed on the television screen. A form of this is demonstrated in
Programming Example 4, a Teaching Aid# in Section 8.
In each of these programs# items are placed at various known locations
on the screen. When the light pen registers are read# the program
compares the values obtained there to the values known to represent
Possible Uses of the Light Pen

ATARI Light Pen Operator's Manual
the position of the test characters on the screen. This information
tells the computer uhat to do next.
You may extend this control function to sense a selected menu item and
perform a complete function. Such functions may include: turning on
the Program Recorder* sounding an alarm* choosing a mathematical
formula to be executed* selecting a specific disk file* and others.
You may use the light pen as a high-speed joystick (game paddle) to
move the cursor to a neui location on the screen directly rather than
using the keyboard or paddle cursor controls. In games such as tic-
tac-toe* chess* or checkers the light pen can "pick up" a specific
item from a selected position on the game board or place that item or
a marker at another game board position.
In business app1ications* an office planner can use the light pen to
pick up a graphics-represented piece of furniture and reposition it in
another area in his graphics-represented room.
You can experiment uiith the ATARI sound generators by plotting one or
more organ keyboards on the screen. You can use the light pen to
"play" each one of the organs by selecting notes from each of the
keyboards. Each key represents one note of a selected sound generator*
and each keyboard represents a separate sound generator.
There are certain applications for uihich keyboard input would be too
complex or time-consuming. In a case like that* the computer can do
all of the work* determining the pen position and plotting items on
the screen on that basis.
A Light Pen Demonstration Program Cassette has been provided to
illustrate such an application. The cassette contains two copies of a
program called PALLET* with an 8K version on Side 1 and a 16K version
on Side 2. Each version allows you to draw with the light pen on the
screen by plotting colored dots at each position occupied by the pen.
The 16R version includes many extra features. These programs are
described in Section 4* ATARI Light Pen Demonstration Program
Cassette. These suggested uses are only a beginning. You will probably
invent many other ways to use the ATARI Light Pen in your own
programs.
Possible Uses of the Light Pen

ATARI Light Pen Operator's Manual
SECTION 3 - CONNECTING THE LIGHT PEN
The light pen connector is exactly like the
connectors. It can be inserted into any one
controller ports on the front of your ATARI
game controller
of the four game
Personal Computer System.
The demonstration
jack #1 (far left
use the pen
the pen into
in th
programs have been written
jack). Later in the manual
to look, at controller
you will be told how to
e other
controller
jacks (see Appendix H). But for nowi insert
jack #1.
Connecting the Light Pen - 5

ATARI Light Pen Operator's Manual
_ . ^
Connecting the Light Pen - 6