On the ATMega AVRs I have used the rolling average filter with four samples in the filters. I did not use the filter to increase resolution. Samples in filter are 10-bit. Result is 10-bit. Say I need filtered data with a bandwidth of 200Hz then I will setup the A/D sampling timer to get the data into the filter at 800Hz rate.

I have to say that I base the use of FULL GND plane and SPLIT GND plane based upon the application at hand. If I have analogue design where there is minimal high current requirement of the device I may very well just use a FULL GND plane. On the other hand if I am doing analogue A/D converter application and there are high current requirements in the design I may use the SPLIT GND plane. A high current load could be understood to be relay driver, MOSFET driver for motor, or even many LEDs that switch on/off.

Michael Karas