thermostat/src/timer.rs

48 lines
1.1 KiB
Rust

use core::cell::RefCell;
use core::ops::Deref;
use cortex_m::interrupt::Mutex;
use cortex_m_rt::exception;
use stm32f4xx_hal::{
rcc::Clocks,
time::U32Ext,
timer::{Timer, Event as TimerEvent},
stm32::SYST,
};
/// Rate in Hz
const TIMER_RATE: u32 = 500;
/// Interval duration in milliseconds
const TIMER_DELTA: u32 = 1000 / TIMER_RATE;
/// Elapsed time in milliseconds
static TIMER_MS: Mutex<RefCell<u32>> = Mutex::new(RefCell::new(0));
/// Setup SysTick exception
pub fn setup(syst: SYST, clocks: Clocks) {
let mut timer = Timer::syst(syst, TIMER_RATE.hz(), clocks);
timer.listen(TimerEvent::TimeOut);
}
/// SysTick exception (Timer)
#[exception]
fn SysTick() {
cortex_m::interrupt::free(|cs| {
*TIMER_MS.borrow(cs)
.borrow_mut() += TIMER_DELTA;
});
}
/// Obtain current time in milliseconds
pub fn now() -> u32 {
cortex_m::interrupt::free(|cs| {
*TIMER_MS.borrow(cs)
.borrow()
.deref()
})
}
/// block for at least `amount` milliseconds
pub fn sleep(amount: u32) {
let start = now();
while now() - start <= amount {}
}