Hi, I just built my first breadboard Arduino (after I smoked my first Uno, 328 was still good). According to the tutorial I followed, to make use of the ADC, I need a low pass filter on pin 20 of the Atmega328 (AVcc)to get rid of power supply noise. Is this necessary? My o-scope shows only a few micro-volts noise even before plugged in to the two caps on the power input cicuit, I can't find anything after them. I want to use an analog accelerometer, not that critical as far as noise goes. If I will need it, any links to a schematic? Or just design my own for transient 60hz noise? Thanks, TomJ
Very few arduino type boards or clones use a low pass filter to the Avcc pin, they just normally wire it to the Vcc pin with a .1ufd bypass cap to ground for some noise filtering. The AVR datasheet for a 328p chip does show a typical and recommended cap/inductor filter for the Avcc if you require the improved noise filtering method. It’s up to you, most normally don’t see the benefit in most applications.
If you're not doing audio work, you can probably get by without it.
Thanks fellas, Nice of you to reply so fast. TomJ