On Sun, Apr 20, 2025 at 12:36 PM Steve Lewis via cctalk <[email protected]> wrote:
> Anyway, just poking around, no specific question here :) Wel, except a > related/unrelated question -- why does MIDI use 5mA current loop? I suspect one reason is that the current loop input can easily be opto-isolated which will avoid ground loop problems. > And is > that why MIDI adopted the joystick port? (IBM original joystick card spec, > didn't it involve measuring electrical discharge? so it is effectively a > current-loop port? is that somewhat accurate?) MIDI doesn't use the joystick port. By that I mean you can't use an original IBM Game Control Adapter (or a clone of it) for MIDI But many older soundcards included a joystick interface (one main use of a soundcard back then was games). And to save connectors/space on the bracket, the MIDI interface was carried over some pins of the same DA15 (probably by only allowing one joystick, the orignal IBM adapter allowed for 2) -tony
