Pins and Needles

[danwinslow]

I have a small IO board that I was considering trying to interface to a joystick port. The board has AD type pin inputs. I was wondering what actually happens electrically to the pins on a joy stick port...that is, if a pin is configured for output, and I write a 1 on it, does the external pin now carry a voltage? I know very little about the hardware side of this kind of interfacing. I see a lot about pins and +5/-5 or 0 volts, which makes me think that turning 'on' a pin means applying a voltage...eh to it, or across it, or whatever. Any clues from you hardware gurus?

[classics]

Dan,

 

The PIA outputs for the joystick ports are push-pull outputs. They are driven to 5v+ for high, and driven to 0v for low.

 

If you need to configure the inputs for your outside device, configure it as a high imepdance TTL compatible input. Turn off any pull-ups, though weak pull-ups like those in PICs wont be strong enough to effect the 0v low state of the PIA pin.

 

Steve