> First, just because someone wrote up a circuit doesn't make it a good one.
> Any idiot can put up a web page.  However in this case the circuit looks
> reasonable enough at first glance.  Second, most of that circuit is not
> relevant to the discussion, which is about how to drive the PIC A/D input.
> That circuit merely shows the A/D input coming from elsewhere.  Note that
> it
> specifically states "Input 0-5V", which is correct.  Your circuit does not
> adhere to that, which is the "really bad" part I was referring to above.
>
> The reason I said "really bad" instead of merely "bad" is that not only
> can't the A/D measure values below ground, but strange and possibly
> damaging
> things can happen to the PIC when you cause enough current to be conducted
> thru a pin protection diode, especially if that happens during powerup.
>

Yes you are right Olin, I bricked one just because of this.

Everything works as expected now, expect some floating issue.
 I ploted direct 0-255 values in Matlab and did the scaling from there,
resolved.
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist