356 lines
12 KiB
Rust
356 lines
12 KiB
Rust
#![macro_use]
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use core::marker::PhantomData;
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use core::task::Poll;
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use embassy::waitqueue::AtomicWaker;
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use embassy_hal_common::drop::OnDrop;
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use embassy_hal_common::into_ref;
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use futures::future::poll_fn;
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use crate::interrupt::{Interrupt, InterruptExt};
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use crate::ppi::{Event, Task};
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use crate::{pac, Peripheral};
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pub(crate) mod sealed {
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use super::*;
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pub trait Instance {
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/// The number of CC registers this instance has.
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const CCS: usize;
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fn regs() -> &'static pac::timer0::RegisterBlock;
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/// Storage for the waker for CC register `n`.
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fn waker(n: usize) -> &'static AtomicWaker;
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}
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pub trait ExtendedInstance {}
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pub trait TimerType {}
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}
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pub trait Instance: Peripheral<P = Self> + sealed::Instance + 'static + Send {
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type Interrupt: Interrupt;
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}
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pub trait ExtendedInstance: Instance + sealed::ExtendedInstance {}
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macro_rules! impl_timer {
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($type:ident, $pac_type:ident, $irq:ident, $ccs:literal) => {
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impl crate::timer::sealed::Instance for peripherals::$type {
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const CCS: usize = $ccs;
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fn regs() -> &'static pac::timer0::RegisterBlock {
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unsafe { &*(pac::$pac_type::ptr() as *const pac::timer0::RegisterBlock) }
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}
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fn waker(n: usize) -> &'static ::embassy::waitqueue::AtomicWaker {
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use ::embassy::waitqueue::AtomicWaker;
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const NEW_AW: AtomicWaker = AtomicWaker::new();
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static WAKERS: [AtomicWaker; $ccs] = [NEW_AW; $ccs];
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&WAKERS[n]
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}
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}
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impl crate::timer::Instance for peripherals::$type {
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type Interrupt = crate::interrupt::$irq;
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}
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};
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($type:ident, $pac_type:ident, $irq:ident) => {
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impl_timer!($type, $pac_type, $irq, 4);
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};
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($type:ident, $pac_type:ident, $irq:ident, extended) => {
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impl_timer!($type, $pac_type, $irq, 6);
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impl crate::timer::sealed::ExtendedInstance for peripherals::$type {}
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impl crate::timer::ExtendedInstance for peripherals::$type {}
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};
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}
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#[repr(u8)]
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pub enum Frequency {
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// I'd prefer not to prefix these with `F`, but Rust identifiers can't start with digits.
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F16MHz = 0,
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F8MHz = 1,
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F4MHz = 2,
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F2MHz = 3,
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F1MHz = 4,
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F500kHz = 5,
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F250kHz = 6,
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F125kHz = 7,
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F62500Hz = 8,
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F31250Hz = 9,
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}
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/// nRF Timer driver.
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///
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/// The timer has an internal counter, which is incremented for every tick of the timer.
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/// The counter is 32-bit, so it wraps back to 0 at 4294967296.
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///
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/// It has either 4 or 6 Capture/Compare registers, which can be used to capture the current state of the counter
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/// or trigger an event when the counter reaches a certain value.
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pub trait TimerType: sealed::TimerType {}
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pub enum Awaitable {}
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pub enum NotAwaitable {}
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impl sealed::TimerType for Awaitable {}
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impl sealed::TimerType for NotAwaitable {}
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impl TimerType for Awaitable {}
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impl TimerType for NotAwaitable {}
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pub struct Timer<'d, T: Instance, I: TimerType = NotAwaitable> {
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phantom: PhantomData<(&'d mut T, I)>,
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}
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impl<'d, T: Instance> Timer<'d, T, Awaitable> {
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pub fn new_awaitable(timer: impl Peripheral<P = T> + 'd, irq: impl Peripheral<P = T::Interrupt> + 'd) -> Self {
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into_ref!(irq);
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irq.set_handler(Self::on_interrupt);
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irq.unpend();
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irq.enable();
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Self::new_irqless(timer)
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}
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}
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impl<'d, T: Instance> Timer<'d, T, NotAwaitable> {
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/// Create a `Timer` without an interrupt, meaning `Cc::wait` won't work.
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///
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/// This can be useful for triggering tasks via PPI
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/// `Uarte` uses this internally.
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pub fn new(timer: impl Peripheral<P = T> + 'd) -> Self {
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Self::new_irqless(timer)
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}
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}
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impl<'d, T: Instance, I: TimerType> Timer<'d, T, I> {
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/// Create a `Timer` without an interrupt, meaning `Cc::wait` won't work.
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///
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/// This is used by the public constructors.
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fn new_irqless(_timer: impl Peripheral<P = T> + 'd) -> Self {
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let regs = T::regs();
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let mut this = Self { phantom: PhantomData };
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// Stop the timer before doing anything else,
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// since changing BITMODE while running can cause 'unpredictable behaviour' according to the specification.
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this.stop();
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// Set the instance to timer mode.
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regs.mode.write(|w| w.mode().timer());
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// Make the counter's max value as high as possible.
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// TODO: is there a reason someone would want to set this lower?
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regs.bitmode.write(|w| w.bitmode()._32bit());
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// Initialize the counter at 0.
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this.clear();
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// Default to the max frequency of the lower power clock
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this.set_frequency(Frequency::F1MHz);
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for n in 0..T::CCS {
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let cc = this.cc(n);
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// Initialize all the shorts as disabled.
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cc.unshort_compare_clear();
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cc.unshort_compare_stop();
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// Initialize the CC registers as 0.
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cc.write(0);
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}
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this
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}
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/// Starts the timer.
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pub fn start(&self) {
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T::regs().tasks_start.write(|w| unsafe { w.bits(1) })
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}
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/// Stops the timer.
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pub fn stop(&self) {
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T::regs().tasks_stop.write(|w| unsafe { w.bits(1) })
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}
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/// Reset the timer's counter to 0.
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pub fn clear(&self) {
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T::regs().tasks_clear.write(|w| unsafe { w.bits(1) })
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}
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/// Returns the START task, for use with PPI.
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///
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/// When triggered, this task starts the timer.
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pub fn task_start(&self) -> Task {
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Task::from_reg(&T::regs().tasks_start)
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}
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/// Returns the STOP task, for use with PPI.
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///
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/// When triggered, this task stops the timer.
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pub fn task_stop(&self) -> Task {
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Task::from_reg(&T::regs().tasks_stop)
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}
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/// Returns the CLEAR task, for use with PPI.
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///
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/// When triggered, this task resets the timer's counter to 0.
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pub fn task_clear(&self) -> Task {
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Task::from_reg(&T::regs().tasks_clear)
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}
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/// Change the timer's frequency.
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///
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/// This will stop the timer if it isn't already stopped,
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/// because the timer may exhibit 'unpredictable behaviour' if it's frequency is changed while it's running.
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pub fn set_frequency(&self, frequency: Frequency) {
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self.stop();
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T::regs()
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.prescaler
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// SAFETY: `frequency` is a variant of `Frequency`,
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// whose values are all in the range of 0-9 (the valid range of `prescaler`).
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.write(|w| unsafe { w.prescaler().bits(frequency as u8) })
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}
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fn on_interrupt(_: *mut ()) {
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let regs = T::regs();
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for n in 0..T::CCS {
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if regs.events_compare[n].read().bits() != 0 {
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// Clear the interrupt, otherwise the interrupt will be repeatedly raised as soon as the interrupt handler exits.
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// We can't clear the event, because it's used to poll whether the future is done or still pending.
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regs.intenclr
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.modify(|r, w| unsafe { w.bits(r.bits() | (1 << (16 + n))) });
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T::waker(n).wake();
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}
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}
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}
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/// Returns this timer's `n`th CC register.
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///
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/// # Panics
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/// Panics if `n` >= the number of CC registers this timer has (4 for a normal timer, 6 for an extended timer).
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pub fn cc(&mut self, n: usize) -> Cc<T, I> {
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if n >= T::CCS {
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panic!("Cannot get CC register {} of timer with {} CC registers.", n, T::CCS);
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}
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Cc {
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n,
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phantom: PhantomData,
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}
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}
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}
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/// A representation of a timer's Capture/Compare (CC) register.
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///
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/// A CC register holds a 32-bit value.
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/// This is used either to store a capture of the timer's current count, or to specify the value for the timer to compare against.
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///
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/// The timer will fire the register's COMPARE event when its counter reaches the value stored in the register.
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/// When the register's CAPTURE task is triggered, the timer will store the current value of its counter in the register
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pub struct Cc<'a, T: Instance, I: TimerType = NotAwaitable> {
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n: usize,
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phantom: PhantomData<(&'a mut T, I)>,
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}
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impl<'a, T: Instance> Cc<'a, T, Awaitable> {
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/// Wait until the timer's counter reaches the value stored in this register.
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///
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/// This requires a mutable reference so that this task's waker cannot be overwritten by a second call to `wait`.
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pub async fn wait(&mut self) {
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let regs = T::regs();
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// Enable the interrupt for this CC's COMPARE event.
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regs.intenset
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.modify(|r, w| unsafe { w.bits(r.bits() | (1 << (16 + self.n))) });
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// Disable the interrupt if the future is dropped.
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let on_drop = OnDrop::new(|| {
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regs.intenclr
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.modify(|r, w| unsafe { w.bits(r.bits() | (1 << (16 + self.n))) });
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});
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poll_fn(|cx| {
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T::waker(self.n).register(cx.waker());
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if regs.events_compare[self.n].read().bits() != 0 {
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// Reset the register for next time
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regs.events_compare[self.n].reset();
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Poll::Ready(())
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} else {
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Poll::Pending
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}
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})
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.await;
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// The interrupt was already disabled in the interrupt handler, so there's no need to disable it again.
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on_drop.defuse();
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}
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}
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impl<'a, T: Instance> Cc<'a, T, NotAwaitable> {}
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impl<'a, T: Instance, I: TimerType> Cc<'a, T, I> {
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/// Get the current value stored in the register.
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pub fn read(&self) -> u32 {
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T::regs().cc[self.n].read().cc().bits()
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}
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/// Set the value stored in the register.
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///
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/// `event_compare` will fire when the timer's counter reaches this value.
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pub fn write(&self, value: u32) {
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// SAFETY: there are no invalid values for the CC register.
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T::regs().cc[self.n].write(|w| unsafe { w.cc().bits(value) })
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}
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/// Capture the current value of the timer's counter in this register, and return it.
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pub fn capture(&self) -> u32 {
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T::regs().tasks_capture[self.n].write(|w| unsafe { w.bits(1) });
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self.read()
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}
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/// Returns this CC register's CAPTURE task, for use with PPI.
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///
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/// When triggered, this task will capture the current value of the timer's counter in this register.
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pub fn task_capture(&self) -> Task {
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Task::from_reg(&T::regs().tasks_capture)
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}
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/// Returns this CC register's COMPARE event, for use with PPI.
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///
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/// This event will fire when the timer's counter reaches the value in this CC register.
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pub fn event_compare(&self) -> Event {
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Event::from_reg(&T::regs().events_compare[self.n])
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}
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/// Enable the shortcut between this CC register's COMPARE event and the timer's CLEAR task.
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///
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/// This means that when the COMPARE event is fired, the CLEAR task will be triggered.
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///
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/// So, when the timer's counter reaches the value stored in this register, the timer's counter will be reset to 0.
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pub fn short_compare_clear(&self) {
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T::regs()
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.shorts
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.modify(|r, w| unsafe { w.bits(r.bits() | (1 << self.n)) })
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}
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/// Disable the shortcut between this CC register's COMPARE event and the timer's CLEAR task.
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pub fn unshort_compare_clear(&self) {
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T::regs()
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.shorts
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.modify(|r, w| unsafe { w.bits(r.bits() & !(1 << self.n)) })
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}
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/// Enable the shortcut between this CC register's COMPARE event and the timer's STOP task.
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///
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/// This means that when the COMPARE event is fired, the STOP task will be triggered.
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///
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/// So, when the timer's counter reaches the value stored in this register, the timer will stop counting up.
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pub fn short_compare_stop(&self) {
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T::regs()
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.shorts
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.modify(|r, w| unsafe { w.bits(r.bits() | (1 << (8 + self.n))) })
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}
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/// Disable the shortcut between this CC register's COMPARE event and the timer's STOP task.
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pub fn unshort_compare_stop(&self) {
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T::regs()
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.shorts
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.modify(|r, w| unsafe { w.bits(r.bits() & !(1 << (8 + self.n))) })
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}
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}
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