AVCC & I2C - Are they linked?

Hello,

I am in the process of making my circuit fully protected against EMI & have a question about the AVCC pin on the Arduino...

In a couple of posts, some people say the adding a low pass filter on the AVCC pin, will make ADC more robust & accurate readings, but is it necessary if I am using A4 & A5 pins for I2C communication? Will this improve the overall performance?

Any answers would be greatly appreciated!

Cheers,

Lee

I2C and the ADC are two completely different bits of hardware. AVCC has nothing to do with I2C.

The AVcc rail supplies the ADC and the analog comparator circuitry (including AREF) - this is nothing to do with the use of pins A4 & A5 as I2C bus.

Of course there is a requirement that AVcc and Vcc differ by less than 0.5V otherwise the pins could not be shared in this manner. The greater the voltage difference between Vcc and AVcc the less noise can be tolerated on Vcc before it affects the analog circuitry - its best if they are nominally the same voltage.

In a couple of posts, some people say the adding a low pass filter on the AVCC pin, will make ADC more robust & accurate readings,

Yes it will do, provided you make a very good grounding (such you do not get noise in via ground loops)..