Add timer implementation

src/lib.rs

@@ -17,3 +17,4 @@ pub mod rcc;
 pub mod serial;
 pub mod spi;
 pub mod time;
+pub mod timers;

src/timers.rs

@@ -0,0 +1,206 @@
+#[cfg(feature = "stm32f030")]
+use crate::stm32::{RCC, TIM1, TIM14, TIM15, TIM16, TIM17, TIM3, TIM6, TIM7};
+#[cfg(feature = "stm32f042")]
+use crate::stm32::{RCC, TIM1, TIM14, TIM16, TIM17, TIM2, TIM3};
+use cortex_m::peripheral::syst::SystClkSource;
+use cortex_m::peripheral::SYST;
+
+use crate::rcc::Clocks;
+use cast::{u16, u32};
+use embedded_hal::timer::{CountDown, Periodic};
+use nb;
+use void::Void;
+
+use crate::time::Hertz;
+
+/// Hardware timers
+pub struct Timer<TIM> {
+    clocks: Clocks,
+    tim: TIM,
+}
+
+/// Interrupt events
+pub enum Event {
+    /// Timer timed out / count down ended
+    TimeOut,
+}
+
+impl Timer<SYST> {
+    /// Configures the SYST clock as a periodic count down timer
+    pub fn syst<T>(mut syst: SYST, timeout: T, clocks: Clocks) -> Self
+    where
+        T: Into<Hertz>,
+    {
+        syst.set_clock_source(SystClkSource::Core);
+        let mut timer = Timer { tim: syst, clocks };
+        timer.start(timeout);
+        timer
+    }
+
+    /// Starts listening for an `event`
+    pub fn listen(&mut self, event: Event) {
+        match event {
+            Event::TimeOut => self.tim.enable_interrupt(),
+        }
+    }
+
+    /// Stops listening for an `event`
+    pub fn unlisten(&mut self, event: Event) {
+        match event {
+            Event::TimeOut => self.tim.disable_interrupt(),
+        }
+    }
+}
+
+impl CountDown for Timer<SYST> {
+    type Time = Hertz;
+
+    fn start<T>(&mut self, timeout: T)
+    where
+        T: Into<Hertz>,
+    {
+        let rvr = self.clocks.sysclk().0 / timeout.into().0 - 1;
+
+        assert!(rvr < (1 << 24));
+
+        self.tim.set_reload(rvr);
+        self.tim.clear_current();
+        self.tim.enable_counter();
+    }
+
+    fn wait(&mut self) -> nb::Result<(), Void> {
+        if self.tim.has_wrapped() {
+            Ok(())
+        } else {
+            Err(nb::Error::WouldBlock)
+        }
+    }
+}
+
+impl Periodic for Timer<SYST> {}
+
+macro_rules! timers {
+    ($($TIM:ident: ($tim:ident, $timXen:ident, $timXrst:ident, $apbenr:ident, $apbrstr:ident),)+) => {
+        $(
+            impl Timer<$TIM> {
+                // XXX(why not name this `new`?) bummer: constructors need to have different names
+                // even if the `$TIM` are non overlapping (compare to the `free` function below
+                // which just works)
+                /// Configures a TIM peripheral as a periodic count down timer
+                pub fn $tim<T>(tim: $TIM, timeout: T, clocks: Clocks) -> Self
+                where
+                    T: Into<Hertz>,
+                {
+                    // NOTE(unsafe) This executes only during initialisation
+                    let rcc = unsafe { &(*RCC::ptr()) };
+
+                    // enable and reset peripheral to a clean slate state
+                    rcc.$apbenr.modify(|_, w| w.$timXen().set_bit());
+                    rcc.$apbrstr.modify(|_, w| w.$timXrst().set_bit());
+                    rcc.$apbrstr.modify(|_, w| w.$timXrst().clear_bit());
+
+                    let mut timer = Timer {
+                        clocks,
+                        tim,
+                    };
+                    timer.start(timeout);
+
+                    timer
+                }
+
+                /// Starts listening for an `event`
+                pub fn listen(&mut self, event: Event) {
+                    match event {
+                        Event::TimeOut => {
+                            // Enable update event interrupt
+                            self.tim.dier.write(|w| w.uie().set_bit());
+                        }
+                    }
+                }
+
+                /// Stops listening for an `event`
+                pub fn unlisten(&mut self, event: Event) {
+                    match event {
+                        Event::TimeOut => {
+                            // Enable update event interrupt
+                            self.tim.dier.write(|w| w.uie().clear_bit());
+                        }
+                    }
+                }
+
+                /// Releases the TIM peripheral
+                pub fn release(self) -> $TIM {
+                    use crate::stm32::RCC;
+                    let rcc = unsafe { &(*RCC::ptr()) };
+                    // Pause counter
+                    self.tim.cr1.modify(|_, w| w.cen().clear_bit());
+                    // Disable timer
+                    rcc.$apbenr.modify(|_, w| w.$timXen().clear_bit());
+                    self.tim
+                }
+            }
+
+            impl CountDown for Timer<$TIM> {
+                type Time = Hertz;
+
+                fn start<T>(&mut self, timeout: T)
+                where
+                    T: Into<Hertz>,
+                {
+                    // pause
+                    self.tim.cr1.modify(|_, w| w.cen().clear_bit());
+                    // restart counter
+                    self.tim.cnt.reset();
+
+                    let frequency = timeout.into().0;
+                    let ticks = self.clocks.pclk().0 / frequency;
+
+                    let psc = u16((ticks - 1) / (1 << 16)).unwrap();
+                    self.tim.psc.write(|w| unsafe { w.psc().bits(psc) });
+
+                    let arr = u16(ticks / u32(psc + 1)).unwrap();
+                    self.tim.arr.write(|w| unsafe { w.bits(u32(arr)) });
+
+                    // start counter
+                    self.tim.cr1.modify(|_, w| w.cen().set_bit());
+                }
+
+                fn wait(&mut self) -> nb::Result<(), Void> {
+                    if self.tim.sr.read().uif().bit_is_clear() {
+                        Err(nb::Error::WouldBlock)
+                    } else {
+                        self.tim.sr.modify(|_, w| w.uif().clear_bit());
+                        Ok(())
+                    }
+                }
+            }
+
+            impl Periodic for Timer<$TIM> {}
+        )+
+    }
+}
+
+#[cfg(any(feature = "stm32f030", feature = "stm32f042",))]
+timers! {
+    TIM1: (tim1, tim1en, tim1rst, apb2enr, apb2rstr),
+    TIM3: (tim3, tim3en, tim3rst, apb1enr, apb1rstr),
+    TIM14: (tim14, tim14en, tim14rst, apb1enr, apb1rstr),
+    TIM16: (tim16, tim16en, tim16rst, apb2enr, apb2rstr),
+    TIM17: (tim17, tim17en, tim17rst, apb2enr, apb2rstr),
+}
+
+#[cfg(any(feature = "stm32f030x8", feature = "stm32f030xc"))]
+timers! {
+    TIM6: (tim6, tim6en, tim6rst, apb1enr, apb1rstr),
+    TIM15: (tim15, tim15en, tim15rst, apb2enr, apb2rstr),
+}
+
+#[cfg(feature = "stm32f030xc")]
+timers! {
+    TIM7: (tim7, tim7en, tim7rst, apb1enr, apb1rstr),
+}
+
+#[cfg(feature = "stm32f042")]
+timers! {
+    TIM2: (tim2, tim2en, tim2rst, apb1enr, apb1rstr),
+}