From PiFace.GitHub.io via PiFace.org.uk


  The eight input pins detect a connection to ground (provided as the ninth pin). The four switches are connected in parallel to the first four input pins. The inputs are pulled up to 5V. This can be turned off so that the inputs float.


From this I surmise the following







simulate this circuit &ndash; Schematic created using CircuitLab

Why does my switch need to be wired in this fashion?
Often I'll set some process off, then change focus to another program and be typing away in a textbox (for example), when the first thing pops up into view, maybe with a Yes / No box which I'd then accidentally interact with as I'm still typing.

I just accidentally sent a license agreement for something that was downloading &amp; installing, to the printer as it popped up once it had downloaded, while I was typing a url into Chrome. If I didn't quickly cancel it I'd have had to wait while 53 pages printed while I reflected on what had happened.

What can application developers, or the OS itself do to minimize these problems?
