Hi,

On 30 May 99 at 1:17, Sean Breheny wrote:
<snip>
> I know that 2 LSB error isn't that bad,but in my case,it is really annoying
> because the actual ADC count gets multiplied by 7 before being displayed on
> an LCD display. SO, if I calibrate it to be correct in one portion of the
> scale, I get as much as 14 or sometimes even 21 counts (after being
> multiplied by 7). Yeah, I know,an 8 bit ADC on a ucontroller is not a
> really precision device and multiplying by 7 is making things worse,but I
> think I could live with 1 LSB of error more easily. MORE IMPORTANTLY, I
> want to make sure I am not doing something dumb with the sleep mode.

I don't think your noise is related to the oscillations not
stopping....
 Just a few ideas:
1. Try reducing your Vcc noise (Try bypassing with 22uF, 0.1uF and
0.01uF both before the regulator and after).  Place 0.1uF near your
PIC's Vcc (and to its ground).
2. Use a ground plane if possible.
3. Route your analog input away from high speed signals to reduce
coupled noise.
4. Filter your analog input (at least with an RC filter, best with
an active filter).
 5. Use some form of digital filtering to get rid of more noise (if
you can sample quicker than your analog signal bandwidth.)

I see no reason why you shouldn't be able to get the noise below
1LSB...

I hope this helps,
Guy - mlsirton@inter.net.il