I'm building a custom interface unit for a game port joystick. To use/test it, I have a CH Products Mach III. (This is the IBM PC version, not the Apple version.) I purchased the joystick for this purpose and have not tested it with an original computer.
I found that the second button was registering as always-pressed. On investigation, there is a resistance of about 60 Ω between "button 2" pin 7 and "ground" pin 4 (pin 5 is absent from the plug) when the button is not pressed, <1 Ω when the button is pressed, and no connection between pin 7 and any other pin. Button 1 behaves more as expected, an open circuit when the button is not pressed.
Is this a special signaling mechanism of some sort, or does it merely indicate that the switch is dirty? (It is not clear how to open the joystick to inspect the circuit, or I would have done this first. Perhaps I'll ask a separate question about that.)
I would ideally like to design the interface unit to be broadly compatible with different models of joysticks (including, possibly, Apple-style joysticks with an alternate socket; and excluding proprietary extensions or anything requiring digital decoding), so I am preferably looking for expectations on button interfacing, perhaps with recommended (or historical) detection thresholds, not just information about this specific joystick.