use core::cell::RefCell; use cortex_m::interrupt::Mutex; use cortex_m_rt::exception; use stm32f4xx_hal::{ rcc::Clocks, time::{U32Ext, MilliSeconds}, timer::{Timer, Event as TimerEvent}, stm32::SYST, }; /// Rate in Hz const TIMER_RATE: u32 = 10; /// Interval duration in milliseconds const TIMER_DELTA: u32 = 1000 / TIMER_RATE; /// Elapsed time in milliseconds static TIMER_MS: Mutex> = 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() -> MilliSeconds { let ms = cortex_m::interrupt::free(|cs| { *TIMER_MS.borrow(cs) .borrow() }); ms.ms() }