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//! Demonstrates initialization of resources in `init`.
#![deny(unsafe_code)]
#![feature(proc_macro)]
#![no_std]
extern crate cortex_m_rtfm as rtfm;
extern crate stm32f103xx;
use rtfm::{app, Threshold};
app! {
device: stm32f103xx,
resources: {
// Usually, resources are initialized with a constant initializer:
static ON: bool = false;
// However, there are cases where this is not possible or not desired.
// For example, there may not be a sensible value to use, or the type may
// not be constructible in a constant (like `Vec`).
//
// While it is possible to use an `Option` in some cases, that requires
// you to properly initialize it and `.unwrap()` it at every use. It
// also consumes more memory.
//
// To solve this, it is possible to defer initialization of resources to
// `init` by omitting the initializer. Doing that will require `init` to
// return the values of all "late" resources.
static IP_ADDRESS: u32;
// PORT is used by 2 tasks, making it a shared resource. This just tests
// another internal code path and is not important for the example.
static PORT: u16;
},
idle: {
// Test that late resources can be used in idle
resources: [IP_ADDRESS],
},
tasks: {
SYS_TICK: {
priority: 1,
path: sys_tick,
resources: [IP_ADDRESS, PORT, ON],
},
EXTI0: {
priority: 2,
path: exti0,
resources: [PORT],
}
}
}
// The signature of `init` is now required to have a specific return type.
fn init(_p: init::Peripherals, _r: init::Resources) -> init::LateResources {
// `init::Resources` does not contain `IP_ADDRESS`, since it is not yet
// initialized.
//_r.IP_ADDRESS; // doesn't compile
// ...obtain value for IP_ADDRESS from EEPROM/DHCP...
let ip_address = 0x7f000001;
init::LateResources {
// This struct will contain fields for all resources with omitted
// initializers.
IP_ADDRESS: ip_address,
PORT: 0,
}
}
fn sys_tick(_t: &mut Threshold, r: SYS_TICK::Resources) {
// Other tasks can access late resources like any other, since they are
// guaranteed to be initialized when tasks are run.
r.IP_ADDRESS;
}
fn exti0(_t: &mut Threshold, _r: EXTI0::Resources) {}
fn idle(_t: &mut Threshold, _r: idle::Resources) -> ! {
loop {
rtfm::wfi();
}
}
|
