AVR-Chat

Stuart Whelan wrote:
> Hi folks,
...
> The Mega8 iterates through the 6 ADC channels.
> 
> I have implemented software smoothing within the chip, but the raw
> hardware signal is bouncing around by up to 4 bits.
> 
> My question are these: What else can I do or should I do to get a
> 'smooth signal'?
> 
> - Should I be using an external clock source?

no

> - Should I be using VCC as my AREF?

Only if it is low noise. Atleast feed it thru an RC filter.

> - Should I be using something other than the Int.Ref 2.56v for AREF?

Not needed. Filter AREF with a cap tho.

> - What would be regarded as a 'smooth' VCC or AREF? My VCC at the moment
> is fluctuating by about 20mV according to the scope.

4 bits is 40mVpk for AREF=5V. Make sure the REF is 1/10th as noisy atleast.

> Any comments, tips suggestions or advice would be most welcome.

Make sure ground pins are connected to a good grounding system.
For extra low noise, don't switch any loads on the same port as
the ADC pins during sampling.