Input drivers and plans for building a multiplexer for the Atari CX80 Trak-Ball. This package is distributed as shareware, please send $5.00 to David Gunderson, 618 East 2nd St. Apt 3, Superior, NE 68978-1904
DESCRIPTION OF FILES
DEMO 1.0 is a BASIC program that pokes a machine language trackball driver into memory. It can be located anywhere in memory where there are 103 bytes free by changing the value of S in line 10. The trackball must be in trackball mode to properly move the pointer. Due to keyboard incompatability it must in joystick mode to type, and in trackball mode to move the pointer. This program does not use the multiplexer.
DEMO 2.0 is a BASIC program that pokes a machine language trackball driver that uses the multiplexer. It can be located anywhere in memory where there are 163 bytes free by changing the value of S in line 10. The trackball must be in trackball mode, and the adaptor must be installed to use this program.
TRACKBALL 1.0 is a GEOS input driver for the trackball. Use CONVERT V2.5 to convert it to GEOS format. Due to keyboard inconpatability you must switch to joystick mode to type, and to trackball mode to move the pointer with TRACKBALL 1.0 installed. You can change the speed of the pointer by changing the minimum velocity using the preference manager.
TRACKBALL 2.0 is a GEOS input driver for the trackball that overcomes the hardware incompatability problem by using the multiplexer. Use CONVERT V2.5 to convert it to GEOS format. The trackball must be in trackball mode and the multiplexer must be inasalled to work properly with TRACKBALL 2.0 installed. You can change the speed of the pointer by changing the minimum velocity using the preference manager.
TRACKBALL.DOC is this file.
MULTIPLEX.SCHEM is a geoPaint file with schematics and diagrams for making the multiplexer. Use CONVERT V2.5 to convert it to GEOS format.
MAKING THE ADAPTOR
CAUTION: You should have a knowledge of basic electronics and soldering before attempting to make the multiplexer. Improper wiring could damage your computer and/or trackball. The author will not be held responsible for any damage to your equipment.
1. Cut the PC board into a 1in. x 5/8in. rectangle so that there is a 6x10 grid of holes. (see multiplex.schem)
2. Solder the 74LS151 IC into the center of the circuit board with the notch pointing toward the male connector. (see multiplex.schem)
3. Solder resistor R1 from pin 5 of IC1 to the corner of the PC board next to the female connector. (see multiplex.schem)
4. Solder a wire from R1 to pin 1 of the female connector. (see mutiplex.schem)
5. Solder the rest of the wires in according the following charts.
IC1 Pin to CN1 Female Pin
-------------------------
7 8
8 8
9 4
10 3
11 2
16 7
IC1 Pin to CN2 Male Pin
------------------------
2 3
3 2
4 1
7 8
8 8
15 4
16 7
6. Solder a wire from pin 6 of the female connector to pin 6 of the male connector.
7. Doubble check wiring and check for solder bridges, cold solder joints, ect.
8. Snap the custom adaptor housing around the completed multiplexer.
9. Insert the trackball cord into the male end of the multiplexer, and the female end of the multiplexer into control port 1.
PARTS LIST
Description Mouser Digi-Key Newark Allied Radio Shack
IC1 74LS151 8 to 1 511-74LS151 DM74LS151N-ND SN74LS151 SN74LS151
CN2 Male 9 pin DIN 152-5009 A2043-ND 76F1329 720-8019 276-1537
Connector
PC Board 400-9032 V1005-ND 38F408 977-8300 276-1395
D sub custom 157-4001
adaptor housing
The Atari CX80 trak-ball can be purchased at the Computer Bargain Store, phone no. (801) 466-8084.
THEORY OF OPERATION
When the trackball is rotated horrizontally it causes pin 2 to toggle. When it is rotated to the left, it causes pin 1 to go low, when it is rotated to the right it causes pin 1 go high. When the trackball is rotated vertically it causes pin 4 to toggle. When it is rotated up, it causes pin 3 to go low, when it is rotated down, it causes pin 3 to go high.
The keyboard and the control ports are connected, so if any of the pins are low while the keyboard is being scanned, it will be falsely interpreted as a keypress. The multiplexer avoids this problem by not reading the trackball while the keyscan is taking place.
Pins 2,3 and 4 of control port 1 are set as outputs and are connected to input selects A,B and C respectively. Pin 1 is set as an input and is connected to the output of IC1. Pin 6 is set as an input and is used to read the button in the same way as it would be read from a joystick. The multiplexer is wired so that when less than 2 of the input select pins on IC1 are low, it selects an unused input, this cuses the IC's output to go high. This is because when a key is pressed it can cause one of the outputs on the control port to go low, if this were to select an input on IC1 that was low, it would pull pin 1 of the control port low, this would interfere with the keyscan. When the keyboard is not being scanned, the input driver programs send codes to the input select pins that select input from pins 1 through 4 on CN2 in order, these inputs are read serially through pin 1 of control port 1. This information is used to move the pointer across the screen.
TROUBLESHOOTING
PROBLEM SOLUTION
Cursor only moves down and to the Trackball is in joystick mode, switch
right. to trackball mode.
Pointer wiggles, but does not move. Install the multiplexer, or use
TRACKBALL 1.0.
Pointer does not move. You are using the multiplexer with
TRACKBALL 1.0, use TRACKBALL 2.0.
The trackball is plugged into port 2,
plug it into port 1.
The multiplexer is not working, check
for improper wiring, solder bridges,
cold solder joints, ect.
Computer shuts down when you plug in Short in the multiplexer, check for
the multiplexer. improper wiring and solder bridges.
