Attribute Macro entry 

#[entry]

Attribute to declare the entry point of the program

Exactly one entry point must be declared in the entire dependency tree.

#[avr_device::entry]
fn main() -> ! {
    loop {
        // ...
    }
}

Constraints

• The entry function must have a signature of [unsafe] fn() -> !.
• This macro requires the avr-device rt crate feature.