Digital Joystick Adapter for IBM PC

Materials needed

• [1] 4066 (Quad Analog Switch)
• [1] 4069 or 7404 (Hex inverter)
• [6] 10 kohm resistor
• [4] 100 kohm resistor
• [1] 9-pin male Dsub connector (for 2600 joystick connection)
• [1] 15-pin male Dsub connector (for PC port connection)

Pinouts

• PC controller port
• 2600 joystick plug
• SMS pad plug
• 4066 Quad analog switch

       _________
   1X |1  \/  14| VCC
   1Y |2      13| 1EN
   2X |3      12| 4EN
   2Y |4 4066 11| 4X
  2EN |5      10| 4Y
  3EN |6       9| 3X
  GND |7_______8| 3Y

• 4069 / 7404 Hex Inverter

       _________
   1A |1  \/  14| VCC
  /1Y |2      13| 6A
   2A |3      12| /6Y
  /2Y |4 7404 11| 5A
   3A |5      10| /5Y
  /3Y |6       9| 4A
  GND |7_______8| /4Y

Schematic

How It Works

The horizontal and vertical axes both work the same, so we only need to look at one of them to see how the whole thing works. Let's look at the horizontal.

• In the center position, two 100k resistors run in parallel between 5V and the H-pot pin of the PC stick port, giving a net resistance of 50k.
• When the stick is pushed east, the 1EN pin of the 4066 is forced low, disengaging one of the 100k resistors. The other 100k resistor is unaffected, and is the only resistance between the 5V and H-pot line.
• When the stick is pushed west, the input to one gate of the hex inverter is forced low, making its output high, which goes to the 2EN pin of the 4066. This engages the 10k resistor between 5V and H-pot, giving a low net resistance between the two.

Enhancements

The PC port can accommodate two joysticks. You can easily create a duplicate circuit to use a second digital stick with the PC. The table below lists the pins for stick 2 equivalent to the stick 1 pins in the schematic.

Function	Stick 1 pins	Stick 2 pins
+5V	1, 8	9, 15
GND	4, 5	12
Horizontal	3	11
Vertical	6	13
Button A	2	14
Button B	7	10

Jay Tilton
06/28/98