stm32: Add the ability to center-align timers

embassy-stm32/src/timer/complementary_pwm.rs

@@ -57,18 +57,20 @@ impl<'d, T: ComplementaryCaptureCompare16bitInstance> ComplementaryPwm<'d, T> {
         _ch4: Option<PwmPin<'d, T, Ch4>>,
         _ch4n: Option<ComplementaryPwmPin<'d, T, Ch4>>,
         freq: Hertz,
+        counting_mode: CountingMode,
     ) -> Self {
-        Self::new_inner(tim, freq)
+        Self::new_inner(tim, freq, counting_mode)
     }
 
-    fn new_inner(tim: impl Peripheral<P = T> + 'd, freq: Hertz) -> Self {
+    fn new_inner(tim: impl Peripheral<P = T> + 'd, freq: Hertz, counting_mode: CountingMode) -> Self {
         into_ref!(tim);
 
         T::enable_and_reset();
 
         let mut this = Self { inner: tim };
 
-        this.inner.set_frequency(freq);
+        this.inner.set_counting_mode(counting_mode);
+        this.set_freq(freq);
         this.inner.start();
 
         this.inner.enable_outputs();
@@ -95,7 +97,12 @@ impl<'d, T: ComplementaryCaptureCompare16bitInstance> ComplementaryPwm<'d, T> {
     }
 
     pub fn set_freq(&mut self, freq: Hertz) {
-        self.inner.set_frequency(freq);
+        let multiplier = if self.inner.get_counting_mode().is_center_aligned() {
+            2u8
+        } else {
+            1u8
+        };
+        self.inner.set_frequency(freq * multiplier);
     }
 
     pub fn get_max_duty(&self) -> u16 {

embassy-stm32/src/timer/mod.rs

@@ -29,10 +29,17 @@ pub(crate) mod sealed {
             Self::regs().cr1().modify(|r| r.set_cen(false));
         }
 
+        /// Reset the counter value to 0
         fn reset(&mut self) {
             Self::regs().cnt().write(|r| r.set_cnt(0));
         }
 
+        /// Set the frequency of how many times per second the timer counts up to the max value or down to 0.
+        ///
+        /// This means that in the default edge-aligned mode,
+        /// the timer counter will wrap around at the same frequency as is being set.
+        /// In center-aligned mode (which not all timers support), the wrap-around frequency is effectively halved
+        /// because it needs to count up and down.
         fn set_frequency(&mut self, frequency: Hertz) {
             let f = frequency.0;
             let timer_f = Self::frequency().0;
@@ -85,8 +92,21 @@ pub(crate) mod sealed {
     pub trait GeneralPurpose16bitInstance: Basic16bitInstance {
         fn regs_gp16() -> crate::pac::timer::TimGp16;
 
-        fn set_count_direction(&mut self, direction: vals::Dir) {
-            Self::regs_gp16().cr1().modify(|r| r.set_dir(direction));
+        fn set_counting_mode(&mut self, mode: CountingMode) {
+            let (cms, dir) = mode.into();
+
+            let timer_enabled = Self::regs().cr1().read().cen();
+            // Changing from edge aligned to center aligned (and vice versa) is not allowed while the timer is running.
+            // Changing direction is discouraged while the timer is running.
+            assert!(!timer_enabled);
+
+            Self::regs_gp16().cr1().modify(|r| r.set_dir(dir));
+            Self::regs_gp16().cr1().modify(|r| r.set_cms(cms))
+        }
+
+        fn get_counting_mode(&self) -> CountingMode {
+            let cr1 = Self::regs_gp16().cr1().read();
+            (cr1.cms(), cr1.dir()).into()
         }
 
         fn set_clock_division(&mut self, ckd: vals::Ckd) {
@@ -293,6 +313,73 @@ impl From<InputTISelection> for stm32_metapac::timer::vals::CcmrInputCcs {
     }
 }
 
+#[repr(u8)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub enum CountingMode {
+    #[default]
+    /// The timer counts up to the reload value and then resets back to 0.
+    EdgeAlignedUp,
+    /// The timer counts down to 0 and then resets back to the reload value.
+    EdgeAlignedDown,
+    /// The timer counts up to the reload value and then counts back to 0.
+    ///
+    /// The output compare interrupt flags of channels configured in output are
+    /// set when the counter is counting down.
+    CenterAlignedDownInterrupts,
+    /// The timer counts up to the reload value and then counts back to 0.
+    ///
+    /// The output compare interrupt flags of channels configured in output are
+    /// set when the counter is counting up.
+    CenterAlignedUpInterrupts,
+    /// The timer counts up to the reload value and then counts back to 0.
+    ///
+    /// The output compare interrupt flags of channels configured in output are
+    /// set when the counter is counting both up or down.
+    CenterAlignedBothInterrupts,
+}
+
+impl CountingMode {
+    pub fn is_edge_aligned(&self) -> bool {
+        match self {
+            CountingMode::EdgeAlignedUp | CountingMode::EdgeAlignedDown => true,
+            _ => false,
+        }
+    }
+
+    pub fn is_center_aligned(&self) -> bool {
+        match self {
+            CountingMode::CenterAlignedDownInterrupts
+            | CountingMode::CenterAlignedUpInterrupts
+            | CountingMode::CenterAlignedBothInterrupts => true,
+            _ => false,
+        }
+    }
+}
+
+impl From<CountingMode> for (vals::Cms, vals::Dir) {
+    fn from(value: CountingMode) -> Self {
+        match value {
+            CountingMode::EdgeAlignedUp => (vals::Cms::EDGEALIGNED, vals::Dir::UP),
+            CountingMode::EdgeAlignedDown => (vals::Cms::EDGEALIGNED, vals::Dir::DOWN),
+            CountingMode::CenterAlignedDownInterrupts => (vals::Cms::CENTERALIGNED1, vals::Dir::UP),
+            CountingMode::CenterAlignedUpInterrupts => (vals::Cms::CENTERALIGNED2, vals::Dir::UP),
+            CountingMode::CenterAlignedBothInterrupts => (vals::Cms::CENTERALIGNED3, vals::Dir::UP),
+        }
+    }
+}
+
+impl From<(vals::Cms, vals::Dir)> for CountingMode {
+    fn from(value: (vals::Cms, vals::Dir)) -> Self {
+        match value {
+            (vals::Cms::EDGEALIGNED, vals::Dir::UP) => CountingMode::EdgeAlignedUp,
+            (vals::Cms::EDGEALIGNED, vals::Dir::DOWN) => CountingMode::EdgeAlignedDown,
+            (vals::Cms::CENTERALIGNED1, _) => CountingMode::CenterAlignedDownInterrupts,
+            (vals::Cms::CENTERALIGNED2, _) => CountingMode::CenterAlignedUpInterrupts,
+            (vals::Cms::CENTERALIGNED3, _) => CountingMode::CenterAlignedBothInterrupts,
+        }
+    }
+}
+
 #[derive(Clone, Copy)]
 pub enum OutputCompareMode {
     Frozen,
@@ -471,9 +558,5 @@ foreach_interrupt! {
                 crate::pac::$inst
             }
         }
-
-
-
-
     };
 }

embassy-stm32/src/timer/simple_pwm.rs

@@ -56,18 +56,20 @@ impl<'d, T: CaptureCompare16bitInstance> SimplePwm<'d, T> {
         _ch3: Option<PwmPin<'d, T, Ch3>>,
         _ch4: Option<PwmPin<'d, T, Ch4>>,
         freq: Hertz,
+        counting_mode: CountingMode,
     ) -> Self {
-        Self::new_inner(tim, freq)
+        Self::new_inner(tim, freq, counting_mode)
     }
 
-    fn new_inner(tim: impl Peripheral<P = T> + 'd, freq: Hertz) -> Self {
+    fn new_inner(tim: impl Peripheral<P = T> + 'd, freq: Hertz, counting_mode: CountingMode) -> Self {
         into_ref!(tim);
 
         T::enable_and_reset();
 
         let mut this = Self { inner: tim };
 
-        this.inner.set_frequency(freq);
+        this.inner.set_counting_mode(counting_mode);
+        this.set_freq(freq);
         this.inner.start();
 
         this.inner.enable_outputs();
@@ -92,7 +94,12 @@ impl<'d, T: CaptureCompare16bitInstance> SimplePwm<'d, T> {
     }
 
     pub fn set_freq(&mut self, freq: Hertz) {
-        self.inner.set_frequency(freq);
+        let multiplier = if self.inner.get_counting_mode().is_center_aligned() {
+            2u8
+        } else {
+            1u8
+        };
+        self.inner.set_frequency(freq * multiplier);
     }
 
     pub fn get_max_duty(&self) -> u16 {

examples/stm32f4/src/bin/pwm.rs

@@ -17,7 +17,7 @@ async fn main(_spawner: Spawner) {
     info!("Hello World!");
 
     let ch1 = PwmPin::new_ch1(p.PE9, OutputType::PushPull);
-    let mut pwm = SimplePwm::new(p.TIM1, Some(ch1), None, None, None, khz(10));
+    let mut pwm = SimplePwm::new(p.TIM1, Some(ch1), None, None, None, khz(10), Default::default());
     let max = pwm.get_max_duty();
     pwm.enable(Channel::Ch1);
 

examples/stm32f4/src/bin/pwm_complementary.rs

@@ -30,6 +30,7 @@ async fn main(_spawner: Spawner) {
         None,
         None,
         khz(10),
+        Default::default(),
     );
 
     let max = pwm.get_max_duty();

examples/stm32g4/src/bin/pwm.rs

@@ -17,7 +17,7 @@ async fn main(_spawner: Spawner) {
     info!("Hello World!");
 
     let ch1 = PwmPin::new_ch1(p.PC0, OutputType::PushPull);
-    let mut pwm = SimplePwm::new(p.TIM1, Some(ch1), None, None, None, khz(10));
+    let mut pwm = SimplePwm::new(p.TIM1, Some(ch1), None, None, None, khz(10), Default::default());
     let max = pwm.get_max_duty();
     pwm.enable(Channel::Ch1);
 

examples/stm32h7/src/bin/pwm.rs

@@ -39,7 +39,7 @@ async fn main(_spawner: Spawner) {
     info!("Hello World!");
 
     let ch1 = PwmPin::new_ch1(p.PA6, OutputType::PushPull);
-    let mut pwm = SimplePwm::new(p.TIM3, Some(ch1), None, None, None, khz(10));
+    let mut pwm = SimplePwm::new(p.TIM3, Some(ch1), None, None, None, khz(10), Default::default());
     let max = pwm.get_max_duty();
     pwm.enable(Channel::Ch1);