//! API for the micro-tick timer (UTICK)
//!
//! The entry point to this API is [`UTICK`].
//!
//! The UTICK peripheral is described in the user manual, chapter 26.
//! It is driven by the FRO 1Mhz clock and has a microsecond resolution.
//!
//! # Examples: led.rs, led_utick.rs
// TODO: move this to drivers section,
// possibly merge with ctimers when they're implemented
use embedded_hal::timer;
use nb;
use void::Void;
use crate::{
raw,
peripherals::{
syscon,
},
typestates::{
init_state,
ClocksSupportUtickToken,
},
};
crate::wrap_stateful_peripheral!(Utick, UTICK0);
pub type EnabledUtick = Utick<init_state::Enabled>;
impl<State> Utick<State> {
pub fn enabled(
mut self,
syscon: &mut syscon::Syscon,
_clocktree_token: &ClocksSupportUtickToken,
) -> EnabledUtick {
syscon.enable_clock(&mut self.raw);
syscon.reset(&mut self.raw);
Utick {
raw: self.raw,
_state: init_state::Enabled(()),
}
}
pub fn disabled(mut self, syscon: &mut syscon::Syscon) -> Utick<init_state::Disabled> {
syscon.disable_clock(&mut self.raw);
Utick {
raw: self.raw,
_state: init_state::Disabled,
}
}
}
// TODO: This does not feel like it belongs here.
impl timer::Cancel for EnabledUtick {
type Error = Void;
fn cancel(&mut self) -> Result<(), Self::Error> {
// A value of 0 stops the timer.
self.raw.ctrl.write(|w| unsafe { w.delayval().bits(0) });
Ok(())
}
}
// TODO: also implement Periodic for UTICK
impl timer::CountDown for EnabledUtick {
type Time = u32;
fn start<T>(&mut self, timeout: T)
where
T: Into<Self::Time>,
{
// The delay will be equal to DELAYVAL + 1 periods of the timer clock.
// The minimum usable value is 1, for a delay of 2 timer clocks. A value of 0 stops the timer.
let time = timeout.into();
// Maybe remove again? Empirically, nothing much happens when
// writing 1 to `delayval`.
assert!(time >= 2);
self.raw
.ctrl
.write(|w| unsafe { w.delayval().bits(time - 1) });
// So... this seems a bit unsafe (what if time is 2?)
// But: without it, in --release builds the timer behaves erratically.
// The UM says this on the topic: "Note that the Micro-tick Timer operates from a different
// (typically slower) clock than the CPU and bus systems. This means there may be a
// synchronization delay when accessing Micro-tick Timer registers."
while self.raw.stat.read().active().bit_is_clear() {}
}
fn wait(&mut self) -> nb::Result<(), Void> {
if self.raw.stat.read().active().bit_is_clear() {
return Ok(());
}
Err(nb::Error::WouldBlock)
}
}
// TODO: Either get rid of `nb` or get rid of this
impl EnabledUtick {
pub fn blocking_wait(&mut self) {
while self.raw.stat.read().active().bit_is_set() {}
}
}