If I compile directly the example programs there are not errors, but if I start a new project with the same code of the example program there are errors: for example the compiler says “undefined reference to print; undefined reference to delay_ms…”. How can I solve these probems ?
It sounds like you did not configure your project to use the pololu_atmega328p library, causing the errors you’re seeing. If you want to use the Pololu AVR Library in a new project in Atmel Studio, you need to configure the AVR/GNU Linker to use the library. You can find that setting in Project > Properties. However, since it sounds like you are not familiar with using Atmel Studio, I recommend using the New Project templates installed by the library and modifying the code for your application.