On Sat, Oct 20, 2018 at 6:52 PM Fred Cisin via cctalk <cctalk@classiccmp.org> wrote:
> Similarly, although they sold a joystick board, they didn't sell > joysticks. DA15 connector for two joysticks. > In some of the documentation, the sketch of a joystick was clearly the > Radio Shack Coco joystick (which needed a different connector) And is electrically different. The CoCo Joystick is a potential divider across the 5V rail. Moving the joystick varies the output voltage (2 voltages per joystick, X and Y). This is fed into a 6 bit ADC (actually a 6 bit DAC, a comparator and some firmware). The IBM PC Joystick (like the Apple ][ ones) is a pair of variable resistors. This are the timing resistors in monostable circuits, acutally an NE558 chip (Think of it as being 4 555 timers always connected as monostables in one package). The software triggers the monostables then sees how long they take to flip back again. I assume the PCjr Joystick is like the PC one, electrically, but I don't feel like going upstairs to check the TechRef. -tony
