Actually, the system I described is TOO simple: Here's my evidence that an Intellivision controller follows a logic even weirder than I suggest and why using a 2600 controller would not work without some modification.
I've explained a system that could use 3 independent buttons, and 5 pins to cover 16 ways and 12 keypad buttons, and 3 dual keypad combinations, one of them is Pause, and one combination for neutral. Apparently there are NO independent controls, no single pin is reserved for any button, joypad direction, or keypad press. All are interrelated to each other. Apparently, pressing ANY 2 controls would mess it up and come up with unpredictable results.
Also if you take apart the controller, there are 16 separate actuators for the 16 separate directions, which makes pad hacking tough, because NE <> N + E
You should try an Atari 2600 compatible joystick; all it needs is a passive pin adapter. It will work correctly for all 2-way, 4-way, and some 8-way, single button games. When the Intellivision N+E pins are activated together it actually produces an ENE direction; so without extra circuitry it won't work properly with 16-way and some 8-way games. With 8-way games it all depends how the diagonals have been set in the program; Snafu,Q-bert, and Venture for example should work correctly. Like I said the four cardinal directions in the Atari joystick would be connected each to one of pins 1 to 4, and the single button is connected to both pins 6+8, and ground to pin 5 on an Intellivision II DE-9 connector.
Edited by mr_me, Sun May 6, 2018 8:54 AM.