Joystick 4-way / 8-way conversion switch
This allows you to convert an 8-way joystick to a 4-way joystick with the flip of a switch. The advantage is that you can buy and mount 8-way joysticks in your cabinet, but be able to play games requiring a 4-way joystick. This is implemented with several logic gates which prevent 2 joystick switches from being closed at the same time (when in 4-way mode).
Two different variations of this circuit are provided. The first can be used for keyboard encoders and keyboard hacks. The second can be used for interfacing to the PC joystick port. The details of each are described below.
The schematics can be downloaded as a .ckt file for Circuitmaker or you can click on the thumbnails for a larger image.
The variation below works with the joystick port of a PC. It puts out an analog signal but disallows diagonal movements by ignoring them.
Keyboard Encoder/Keyboard Hack Version
The last variation listed here will work with a keyboard encoder or hacked keyboard setup. In the case of a keyboard encoder, ground is connected to the emitter of each transistor and a discrete input is connected to the collector.
To make this work with a hacked keyboard, you'll have to experiment a little. Take 2 leads that you know produce the keystroke you want. Put one lead on the collector and the other on the emitter. Try the circuit and if it doesn't work, reverse the leads.
Second Chance Arcade