rex@cs.su.oz (Rex Di Bona) (03/12/91)
In article <1991Mar12.083628.11466@casbah.acns.nwu.edu> squishy@casbah.acns.nwu.edu (Shishin Yamada) writes: > The 558 is probably used as with a potentiometer in the joystick as an > oscillator. The oscillator is then used to 'count' the position of the > joystick by the oscillators frequency. (I dunno for sure, as I am a Mac > Man. It may even be set up as a one-shot, like the old Apple II). The way the original pc did this was to use the 555 as a one shot, with the delay dependent upon the position of the joystick, the joystick positioning loop would fire the one shot, and the furiously loop waiting for the output to drop again, counting one per loop. Voila, instant a->d converter :-) It's not a bad idea, especially if you are scrimping on hardware, but, hey, it works :-) -------- Rex di Bona (rex@cs.su.oz.au) Penguin Lust is NOT immoral