Do I need to connect the AREF pin

Hi,

I am making my own ATmega328p AU based project. I am connecting a capacitive touch switch to D4 and Serial output at pins 10 and 11. Do I need to connect AREF to ground via capacitor?

Cheers,
Mike.

Why do you think you need to do that?

When looking at Arduino Uno schematics it has the AREF connected to ground via a capacitor.

So why would you add another?

I am doing my own PCB.

If you are not using the analog inputs you don't need it.

The datasheet for the ATmega chip says:

Internal reference voltages of nominally 1.1V or AVCC are provided On-chip. The voltage reference may be externally
decoupled at the AREF pin by a capacitor for better noise performance.

There are a few approaches.

  1. Do it because Arduino did
  2. Review the requirements in the Atmega328P datasheet
  3. Research ADCs and determine why someone decided to put it there.

Personally I would opt to start with #2, the answer is probably in the datasheet.

s200bym:
... Do I need to connect AREF to ground via capacitor?
...

No.

What is the cost to put the pads on the PCB?

what 6the effort to add it after you have boards Made and find you want it n?

Thanks for your replies guys.

dave-in-nj:
What is the cost to put the pads on the PCB?

what 6the effort to add it after you have boards Made and find you want it n?

I was thinking of having it in the circuit and not populating it unless needed the only cost difference would be the cost of the capacitor which is pennies.

Thanks,
Mike.

The AREF pin is not used if you don't use the ADC converters.
A capacitor to ground improves the noise immunity.

If you don't use the ADC, you can leave it unconnected, but the recommandation to add pads for a cap is what you should do... One never knows !