First working draft of a lptim driver

This driver is able to PWM a pin

4 files changed, 244 insertions, 0 deletions

diff --git a/embassy-stm32/build.rs b/embassy-stm32/build.rs
index 1984a1420..33985a3f4 100644
--- a/embassy-stm32/build.rs
+++ b/embassy-stm32/build.rs
@@ -1015,6 +1015,8 @@ fn main() {
         (("hrtim", "CHE2"), quote!(crate::hrtim::ChannelEComplementaryPin)),
         (("hrtim", "CHF1"), quote!(crate::hrtim::ChannelFPin)),
         (("hrtim", "CHF2"), quote!(crate::hrtim::ChannelFComplementaryPin)),
+        (("lptim", "CH1"), quote!(crate::lptim::Channel1Pin)),
+        (("lptim", "CH2"), quote!(crate::lptim::Channel1Pin)),
         (("sdmmc", "CK"), quote!(crate::sdmmc::CkPin)),
         (("sdmmc", "CMD"), quote!(crate::sdmmc::CmdPin)),
         (("sdmmc", "D0"), quote!(crate::sdmmc::D0Pin)),
diff --git a/embassy-stm32/src/lib.rs b/embassy-stm32/src/lib.rs
index 98695e738..451f595e0 100644
--- a/embassy-stm32/src/lib.rs
+++ b/embassy-stm32/src/lib.rs
@@ -89,6 +89,8 @@ pub mod i2s;
 pub mod ipcc;
 #[cfg(feature = "low-power")]
 pub mod low_power;
+#[cfg(lptim)]
+pub mod lptim;
 #[cfg(ltdc)]
 pub mod ltdc;
 #[cfg(opamp)]
diff --git a/embassy-stm32/src/lptim/mod.rs b/embassy-stm32/src/lptim/mod.rs
new file mode 100644
index 000000000..3cf95149e
--- /dev/null
+++ b/embassy-stm32/src/lptim/mod.rs
@@ -0,0 +1,145 @@
+//! Low-power timer (LPTIM)
+
+mod traits;
+
+use core::marker::PhantomData;
+
+use embassy_hal_internal::{into_ref, PeripheralRef};
+pub use traits::Instance;
+
+use crate::gpio::{AfType, AnyPin, OutputType, Speed};
+// use crate::time::Hertz;
+use crate::{rcc, Peripheral};
+
+/// LPTIM master instance.
+pub struct Master<T: Instance> {
+    phantom: PhantomData<T>,
+}
+
+/// LPTIM channel 1 instance.
+pub struct Ch1<T: Instance> {
+    phantom: PhantomData<T>,
+}
+
+/// LPTIM channel 2 instance.
+pub struct Ch2<T: Instance> {
+    phantom: PhantomData<T>,
+}
+
+trait SealedChannel<T: Instance> {
+    fn raw() -> usize;
+}
+
+///  channel instance trait.
+#[allow(private_bounds)]
+pub trait Channel<T: Instance>: SealedChannel<T> {}
+
+/// LPTIM PWM pin.
+pub struct PwmPin<'d, T, C> {
+    _pin: PeripheralRef<'d, AnyPin>,
+    phantom: PhantomData<(T, C)>,
+}
+
+macro_rules! channel_impl {
+    ($new_chx:ident, $channel:tt, $ch_num:expr, $pin_trait:ident) => {
+        impl<'d, T: Instance> PwmPin<'d, T, $channel<T>> {
+            #[doc = concat!("Create a new ", stringify!($channel), " PWM pin instance.")]
+            pub fn $new_chx(pin: impl Peripheral<P = impl $pin_trait<T>> + 'd) -> Self {
+                into_ref!(pin);
+                critical_section::with(|_| {
+                    pin.set_low();
+                    pin.set_as_af(
+                        pin.af_num(),
+                        AfType::output(OutputType::PushPull, Speed::VeryHigh),
+                    );
+                });
+                PwmPin {
+                    _pin: pin.map_into(),
+                    phantom: PhantomData,
+                }
+            }
+        }
+
+        impl<T: Instance> SealedChannel<T> for $channel<T> {
+            fn raw() -> usize {
+                $ch_num
+            }
+        }
+        impl<T: Instance> Channel<T> for $channel<T> {}
+    };
+}
+
+channel_impl!(new_ch1, Ch1, 0, Channel1Pin);
+channel_impl!(new_ch2, Ch2, 1, Channel2Pin);
+
+/// Struct used to divide a high resolution timer into multiple channels
+pub struct Pwm<'d, T: Instance> {
+    _inner: PeripheralRef<'d, T>,
+    /// Master instance.
+    pub master: Master<T>,
+    /// Channel 1.
+    pub ch_1: Ch1<T>,
+    /// Channel 2.
+    pub ch_2: Ch2<T>,
+}
+
+impl<'d, T: Instance> Pwm<'d, T> {
+    /// Create a new LPTIM driver.
+    ///
+    /// This splits the LPTIM into its constituent parts, which you can then use individually.
+    pub fn new(
+        tim: impl Peripheral<P = T> + 'd,
+        _ch1: Option<PwmPin<'d, T, Ch1<T>>>,
+        _ch2: Option<PwmPin<'d, T, Ch2<T>>>,
+    ) -> Self {
+        Self::new_inner(tim)
+    }
+
+    fn new_inner(tim: impl Peripheral<P = T> + 'd) -> Self {
+        into_ref!(tim);
+
+        rcc::enable_and_reset::<T>();
+
+        T::regs().cr().modify(|w| w.set_enable(true));
+
+        // Set frequency. Should be configurable.
+        // By default, 16MHz. We want 440Hz.
+        // That's 36363 cycles
+        T::regs().arr().write_value(stm32_metapac::lptim::regs::Arr(36363));
+
+        // Set duty cycle. Should be configurable. Should take care of channel too (only Ch1 now)
+        T::regs().ccr(0).write_value(stm32_metapac::lptim::regs::Ccr(18181));
+
+        // Enable channel as PWM. Default state anyway. Implement later.
+        // T::regs().ccmr().modify(|w| {
+        //     w.set_ccsel(0, 0);
+        //     w.set_ccsel(1, 0);
+        // })
+
+        // Enable output on pins. Should care about the channels!
+        T::regs().ccmr().modify(|w| {
+            w.set_cce(0, true);
+            w.set_cce(1, true);
+        });
+
+        Self {
+            _inner: tim,
+            master: Master { phantom: PhantomData },
+            ch_1: Ch1 { phantom: PhantomData },
+            ch_2: Ch2 { phantom: PhantomData },
+        }
+    }
+
+    /// Start
+    pub fn start(&mut self) {
+        T::regs().cr().modify(|w| w.set_cntstrt(true));
+    }
+
+    /// Stop
+    pub fn stop(&mut self) {
+        T::regs().cr().modify(|w| w.set_cntstrt(false));
+    }
+}
+
+pin_trait!(Channel1Pin, Instance);
+pin_trait!(Channel2Pin, Instance);
diff --git a/embassy-stm32/src/lptim/traits.rs b/embassy-stm32/src/lptim/traits.rs
new file mode 100644
index 000000000..a8f890a78
--- /dev/null
+++ b/embassy-stm32/src/lptim/traits.rs
@@ -0,0 +1,95 @@
+use crate::rcc::RccPeripheral;
+use crate::time::Hertz;
+
+#[repr(u8)]
+#[derive(Clone, Copy)]
+pub(crate) enum Prescaler {
+    Div1 = 1,
+    Div2 = 2,
+    Div4 = 4,
+    Div8 = 8,
+    Div16 = 16,
+    Div32 = 32,
+    Div64 = 64,
+    Div128 = 128,
+}
+
+impl From<Prescaler> for u8 {
+    fn from(val: Prescaler) -> Self {
+        match val {
+            Prescaler::Div1 => 0b000,
+            Prescaler::Div2 => 0b001,
+            Prescaler::Div4 => 0b010,
+            Prescaler::Div8 => 0b011,
+            Prescaler::Div16 => 0b100,
+            Prescaler::Div32 => 0b101,
+            Prescaler::Div64 => 0b110,
+            Prescaler::Div128 => 0b111,
+        }
+    }
+}
+
+impl From<u8> for Prescaler {
+    fn from(val: u8) -> Self {
+        match val {
+            0b000 => Prescaler::Div1,
+            0b001 => Prescaler::Div2,
+            0b010 => Prescaler::Div4,
+            0b011 => Prescaler::Div8,
+            0b100 => Prescaler::Div16,
+            0b101 => Prescaler::Div32,
+            0b110 => Prescaler::Div64,
+            0b111 => Prescaler::Div128,
+            _ => unreachable!(),
+        }
+    }
+}
+
+impl Prescaler {
+    pub fn compute_min_high_res(val: u32) -> Self {
+        *[
+            Prescaler::Div1,
+            Prescaler::Div2,
+            Prescaler::Div4,
+            Prescaler::Div8,
+            Prescaler::Div16,
+            Prescaler::Div32,
+            Prescaler::Div64,
+            Prescaler::Div128,
+        ]
+        .iter()
+        .skip_while(|psc| **psc as u32 <= val)
+        .next()
+        .unwrap()
+    }
+
+    pub fn compute_min_low_res(val: u32) -> Self {
+        *[Prescaler::Div32, Prescaler::Div64, Prescaler::Div128]
+            .iter()
+            .skip_while(|psc| **psc as u32 <= val)
+            .next()
+            .unwrap()
+    }
+}
+
+pub(crate) trait SealedInstance: RccPeripheral {
+    fn regs() -> crate::pac::lptim::LptimAdv;
+}
+
+/// LPTIM instance trait.
+#[allow(private_bounds)]
+pub trait Instance: SealedInstance + 'static {}
+
+foreach_interrupt! {
+    ($inst:ident, lptim, LPTIM_ADV, UP, $irq:ident) => {
+        impl SealedInstance for crate::peripherals::$inst {
+            fn regs() -> crate::pac::lptim::LptimAdv {
+                crate::pac::$inst
+            }
+        }
+
+        impl Instance for crate::peripherals::$inst {
+
+        }
+    };
+}