timers.rs

use embedded_time::duration::Microseconds;
use rp2040_hal::pac::timer::RegisterBlock;
use rp2040_hal::pac::TIMER;

pub struct Timer {
    _timer: TIMER,
}

impl Timer {
    pub fn new(timer: TIMER) -> Self {
        Self { _timer: timer }
    }

    pub fn split(self) -> (Timer0, Timer1, Timer2, Timer3) {
        // HERE BE DRAGONS

        // # Safety
        //
        // We know that we are the sole owner of TIMER, and that TIMER is a
        // simple wrapper around a pointer to its RegisterBlock.
        // We know that each TimerX implementation only touches its own
        // addresses, so having multiple references to this RegisterBlock
        // is fine.

        (
            Timer0(unsafe { &*TIMER::ptr() }),
            Timer1(unsafe { &*TIMER::ptr() }),
            Timer2(unsafe { &*TIMER::ptr() }),
            Timer3(unsafe { &*TIMER::ptr() }),
        )
    }
}

macro_rules! impl_timer {
    ($n: tt: $name: ident ($timer_alarm:ident, $int_alarm: ident)) => {
        pub struct $name(&'static RegisterBlock);

        impl $name {
            pub fn on_interrupt(&self) {
                self.0.intr.modify(|_, w| w.$int_alarm().set_bit());
            }

            pub fn trigger_now(&self) {
                self.start_countdown(Microseconds(0u32));
            }

            pub fn start_countdown<TIME: core::convert::TryInto<Microseconds>>(
                &self,
                countdown: TIME,
            ) {
                let time = match countdown.try_into() {
                    Ok(time) => time,
                    Err(_) => panic!("Invalid time"),
                };
                cortex_m::interrupt::free(|_| {
                    self.0.$timer_alarm.write(|w| unsafe {
                        w.bits(self.0.timelr.read().bits().wrapping_add(time.0))
                    });
                    self.0.inte.modify(|_, w| w.$int_alarm().set_bit());
                });
            }
        }

        // we have a static reference to a RegisterBlock, but we know all instance have unique access
        // see Timer::split() for more information
        unsafe impl Send for $name {}
    };
}

impl_timer!(0: Timer0(alarm0, alarm_0));
impl_timer!(1: Timer1(alarm1, alarm_1));
impl_timer!(2: Timer2(alarm2, alarm_2));
impl_timer!(3: Timer3(alarm3, alarm_3));