RTIC hello

RTIC, Real-Time Interrupt-driven Concurrency, is a framework for building event-driven, time-sensitive applications.

✅ Open the nrf52-code/usb-app/src/bin/rtic-hello.rs file.

RTIC applications are written in RTIC's Domain Specific Language (DSL). The DSL extends Rust syntax with custom attributes like #[init] and #[idle].

RTIC makes a clearer distinction between the application's initialization phase, the #[init] function, and the application's main loop or main logic, the #[idle] function. The initialization phase runs with interrupts disabled and interrupts are re-enabled before the idle function is executed.

rtic::app is a procedural macro that generates extra Rust code, in addition to the user's functions. The fully expanded version of the macro can be found in the file target/rtic-expansion.rs. This file will contain the expansion of the procedural macro for the last compiled RTIC application.

✅ Build the rtic-hello example and look at the generated rtic-expansion.rs file.

You can use rustfmt on target/rtic-expansion.rs to make the generated code easier to read. Among other things, the file should contain the following lines. Note that interrupts are disabled during the execution of the init function:

#[doc(hidden)] #[no_mangle] unsafe extern "C" fn main() -> ! { rtic::export::interrupt::disable(); let mut core: rtic::export::Peripherals = rtic::export::Peripherals::steal().into(); #[inline(never)] fn __rtic_init_resources<F>(f: F) where F: FnOnce(), { f(); } let mut executors_size = 0; extern "C" { pub static _stack_start: u32; pub static __ebss: u32; } let stack_start = &_stack_start as *const _ as u32; let ebss = &__ebss as *const _ as u32; if stack_start > ebss { if rtic::export::msp::read() <= ebss { panic!("Stack overflow after allocating executors"); } } __rtic_init_resources(|| { let (shared_resources, local_resources) = init(init::Context::new(core.into(), executors_size)); rtic::export::interrupt::enable(); }); idle(idle::Context::new()) }