ADC triggered by Timer0 atmega328

antoniominighin:
last but not least, how do I write code inside the post?

Create your program (sketch) in the Arduino IDE, and then carry out the following steps:
(1) Select the entire codes of the IDE by pressing Cntrl+A.
(2) Copy the selected codes of Step-1.
(3) Click on the symbol </> (called code tags) of the Toolbar of your posting window. Press Cntrl+V.

void setup() 
{
  // put your setup code here, to run once:

}

void loop() 
{
  // put your main code here, to run repeatedly:

}