How to distinguish Arduino's models at compile time?

This is a question that you probably already asked yourself when trying to write code that must work with different Arduino's variants. Indeed, when using I2C, timers or PWM, the pins concerned on the Arduino Uno for these operations are different from Arduino Mega or form Due, etc. Hence, how to avoid the multiplication of the source files, of the classes or to excessively overload functions?

Solution: use conditional compilation!

In this short note we try to explain how to do that. Indeed, digging into the avr include files (see io.h for example) one can find the following constants are used:

__AVR_ATmega328P__
__AVR_ATmega328__

These are used to recognize that we are compiling for Arduino Uno. For the Arduino Mega we find:

__AVR_ATmega1280__
__AVR_ATmega2560__

Therefore your code might look like:

#if defined(__AVR_ATmega328P__) || defined(__AVR_ATmega328P__)
  
  [your arduino uno code here]
  
#elif defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)

  [your arduino mega code here]

Enjoy!