Usually, a timeout is performed after no user activity on the user interface after a give length of time. Typically a user interface will have buttons that are monitored. It is normally sufficient to OR all button signals and use that to trigger a retriggerable one-shot to provide the timeout. If you absolutely need to monitor analogs or serials, then use an anlalog/serial one-shot on those signals to generate a pulse every time they change and feed that into the OR with the digitals.
However, don't over think it. What really needs to be monitored to determine activity timeout? Narrow it down to the essential things. Also, if you are new to programming, be aware of what you are feeding into the OR, make sure they are signals that are only momentary, i.e. button presses or signals that come via a one-shot, otherwise a digital that is held high will mask other transient signals and the retriggerable one-shot will not be retriggered.
Lindsay
