Homebrew PCBs

On Tuesday 31 August 2004 12:23 am, ron amundson wrote:
> > > All one would need to do, is add some type of position encoding to the
> > > mouse wheel, and one would be all set.

> > Nah,  that'll all be handled in the software.  As would the resolution, 
> > for that matter.

> Could you elaborate as to how..... Especially in a power down condition
> where upon one could loose track.

To what,  keep track of the "switch position"?  Store a value in a ram chip 
somewhere.  If it needs to stick around store it in a battery-backed ram.  
You can stuff an awful lot of info into a pretty small (2048 byte) part...

> I take it, there is some trick, as many devices, use relative rather than
> absolute positioning.

It's just a matter of keeping track of "where you were" and using the 
direction of rotation to figure out "where you're going" and how fast. What 
happens when you fire up software that uses a mouse?  I see a lot of stuff 
assuming that the pointer should be in the center of the screen...

> WIthout a home position to index off of, it would seem one could loose the
> position of the pointer if it were turned and power was off.... Or is it
> interrupt driven such that the micro stays alive and wakes up should the
> shaft be turned???

I think this is getting into system design now.  What you'd do depends on what 
you were trying to use this idea for...