I'm current using an Arduino as standalone with the ATMEGA328 chip. If in this project I'm not going to use the ADC do I have to connect AREF, AVCC and AGND? Not connecting these can make my PCB simpler.
I got into a bit of a tiffy because of this before, but Ill say it again, no, only if you have no use for analog inputAGND according to the stuffy shirt bunch should be connected, though I have had an atmega328p running though all sorts of "tapping the limits" abuse with only one ground connected, in a 85 degree C 85% humidity environmental chamber for over 2000 hours with no performance issues as of last sample.
1.1.7 AVCCAVCC is the supply voltage pin for the A/D Converter, PC3:0, and ADC7:6. It should be externallyconnected to VCC, even if the ADC is not used. If the ADC is used, it should be connected to VCCthrough a low-pass filter. Note that PC6..4 use digital supply voltage, VCC.
If you have any problems with it you will get no help from anyone.
Why do you think these recommendations are made?
Do you think it is is people being stupid?
Remember Challenger and the O rings? Engineers were ignored then as well.
Obviously you have never talked to anyone at Atmel about support