Sketch for the schematics of a driving controller compatible with Atari 2600 and MSX at the same time.

The circuit uses a rotary switch with integrated push button, and one extra button.

The integrated switch for the rotary encoder connects pin 9 (GROUND on MSX) to pin 7 (Trigger B on MSX). The common return for the extra push button and for the rotary switch is on pin 8 (PULSE) that is driven low by BIOS by default.

When used on Atari 2600 the integrated button works as a positive drive the right  paddle input, pretty much like the thumb button on the omega race booster grip (or the LEFT button of a 7800 controller).