Merge #455

455: simple_playback api from nrf sdk r=Dirbaio a=jacobrosenthal

Port of the nrf_drv_pwm_simple_playback call from the nordic sdk that allows you to set up a sequence to play across leds with no interaction necessary using the 'shorts' registers to trigger looping sequences



Co-authored-by: Jacob Rosenthal <jacobrosenthal@gmail.com>

embassy-nrf/src/pwm.rs

@@ -1,54 +1,78 @@
 #![macro_use]
 
-use core::cell::UnsafeCell;
 use core::marker::PhantomData;
 use core::sync::atomic::{compiler_fence, Ordering};
 use embassy::util::Unborrow;
 use embassy_hal_common::unborrow;
 
 use crate::gpio::sealed::Pin as _;
-use crate::gpio::OptionalPin as GpioOptionalPin;
+use crate::gpio::{AnyPin, OptionalPin as GpioOptionalPin};
 use crate::interrupt::Interrupt;
 use crate::pac;
+use crate::util::slice_in_ram_or;
 
-#[derive(Debug, Eq, PartialEq, Clone, Copy)]
+/// SimplePwm is the traditional pwm interface you're probably used to, allowing
-pub enum Prescaler {
+/// to simply set a duty cycle across up to four channels.
-    Div1,
+pub struct SimplePwm<'d, T: Instance> {
-    Div2,
-    Div4,
-    Div8,
-    Div16,
-    Div32,
-    Div64,
-    Div128,
-}
-
-/// Interface to the UARTE peripheral
-pub struct Pwm<'d, T: Instance> {
     phantom: PhantomData<&'d mut T>,
+    duty: [u16; 4],
+    ch0: Option<AnyPin>,
+    ch1: Option<AnyPin>,
+    ch2: Option<AnyPin>,
+    ch3: Option<AnyPin>,
 }
 
-impl<'d, T: Instance> Pwm<'d, T> {
+/// SequencePwm allows you to offload the updating of a sequence of duty cycles
-    /// Creates the interface to a UARTE instance.
+/// to up to four channels, as well as repeat that sequence n times.
-    /// Sets the baud rate, parity and assigns the pins to the UARTE peripheral.
+pub struct SequencePwm<'d, T: Instance> {
+    phantom: PhantomData<&'d mut T>,
+    ch0: Option<AnyPin>,
+    ch1: Option<AnyPin>,
+    ch2: Option<AnyPin>,
+    ch3: Option<AnyPin>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[non_exhaustive]
+pub enum Error {
+    /// Max Sequence size is 32767
+    SequenceTooLong,
+    /// Min Sequence count is 1
+    SequenceTimesAtLeastOne,
+    /// EasyDMA can only read from data memory, read only buffers in flash will fail.
+    DMABufferNotInDataMemory,
+}
+
+impl<'d, T: Instance> SequencePwm<'d, T> {
+    /// Creates the interface to a `SequencePwm`.
+    ///
+    /// Must be started by calling `start`
     ///
     /// # Safety
     ///
-    /// The returned API is safe unless you use `mem::forget` (or similar safe mechanisms)
+    /// The returned API is safe unless you use `mem::forget` (or similar safe
-    /// on stack allocated buffers which which have been passed to [`send()`](Pwm::send)
+    /// mechanisms) on stack allocated buffers which which have been passed to
-    /// or [`receive`](Pwm::receive).
+    /// [`new()`](SequencePwm::new).
     #[allow(unused_unsafe)]
-    pub fn new(
+    pub fn new<'a>(
         _pwm: impl Unborrow<Target = T> + 'd,
         ch0: impl Unborrow<Target = impl GpioOptionalPin> + 'd,
         ch1: impl Unborrow<Target = impl GpioOptionalPin> + 'd,
         ch2: impl Unborrow<Target = impl GpioOptionalPin> + 'd,
         ch3: impl Unborrow<Target = impl GpioOptionalPin> + 'd,
-    ) -> Self {
+        config: SequenceConfig,
+        sequence: &'a [u16],
+    ) -> Result<Self, Error> {
+        slice_in_ram_or(sequence, Error::DMABufferNotInDataMemory)?;
+
+        if sequence.len() > 32767 {
+            return Err(Error::SequenceTooLong);
+        }
+
         unborrow!(ch0, ch1, ch2, ch3);
 
         let r = T::regs();
-        let s = T::state();
 
         if let Some(pin) = ch0.pin_mut() {
             pin.set_low();
@@ -66,6 +90,9 @@ impl<'d, T: Instance> Pwm<'d, T> {
             pin.set_low();
             pin.conf().write(|w| w.dir().output());
         }
+
+        // if NoPin provided writes disconnected (top bit 1) 0x80000000 else
+        // writes pin number ex 13 (0x0D) which is connected (top bit 0)
         r.psel.out[0].write(|w| unsafe { w.bits(ch0.psel_bits()) });
         r.psel.out[1].write(|w| unsafe { w.bits(ch1.psel_bits()) });
         r.psel.out[2].write(|w| unsafe { w.bits(ch2.psel_bits()) });
@@ -73,15 +100,306 @@ impl<'d, T: Instance> Pwm<'d, T> {
 
         // Disable all interrupts
         r.intenclr.write(|w| unsafe { w.bits(0xFFFF_FFFF) });
+        r.shorts.reset();
 
         // Enable
         r.enable.write(|w| w.enable().enabled());
 
         r.seq0
             .ptr
-            .write(|w| unsafe { w.bits(&s.duty as *const _ as u32) });
+            .write(|w| unsafe { w.bits(sequence.as_ptr() as u32) });
+        r.seq0
+            .cnt
+            .write(|w| unsafe { w.bits(sequence.len() as u32) });
+        r.seq0.refresh.write(|w| unsafe { w.bits(config.refresh) });
+        r.seq0
+            .enddelay
+            .write(|w| unsafe { w.bits(config.end_delay) });
+
+        r.seq1
+            .ptr
+            .write(|w| unsafe { w.bits(sequence.as_ptr() as u32) });
+        r.seq1
+            .cnt
+            .write(|w| unsafe { w.bits(sequence.len() as u32) });
+        r.seq1.refresh.write(|w| unsafe { w.bits(config.refresh) });
+        r.seq1
+            .enddelay
+            .write(|w| unsafe { w.bits(config.end_delay) });
+
+        r.decoder.write(|w| {
+            w.load().bits(config.sequence_load as u8);
+            w.mode().refresh_count()
+        });
+
+        r.mode.write(|w| match config.counter_mode {
+            CounterMode::UpAndDown => w.updown().up_and_down(),
+            CounterMode::Up => w.updown().up(),
+        });
+        r.prescaler
+            .write(|w| w.prescaler().bits(config.prescaler as u8));
+        r.countertop
+            .write(|w| unsafe { w.countertop().bits(config.top) });
+
+        Ok(Self {
+            phantom: PhantomData,
+            ch0: ch0.degrade_optional(),
+            ch1: ch1.degrade_optional(),
+            ch2: ch2.degrade_optional(),
+            ch3: ch3.degrade_optional(),
+        })
+    }
+
+    /// Start or restart playback
+    #[inline(always)]
+    pub fn start(&self, times: SequenceMode) -> Result<(), Error> {
+        if let SequenceMode::Times(0) = times {
+            return Err(Error::SequenceTimesAtLeastOne);
+        }
+        let r = T::regs();
+
+        self.stop();
+
+        r.enable.write(|w| w.enable().enabled());
+
+        // defensive before seqstart
+        compiler_fence(Ordering::SeqCst);
+
+        match times {
+            // just the one time, no loop count
+            SequenceMode::Times(1) => {
+                r.loop_.write(|w| w.cnt().disabled());
+                // tasks_seqstart() doesn't exist in all svds so write its bit instead
+                r.tasks_seqstart[0].write(|w| unsafe { w.bits(0x01) });
+            }
+            // loop count is how many times to play BOTH sequences
+            // 2 total  (1 x 2)
+            // 3 total, (2 x 2) - 1
+            SequenceMode::Times(n) => {
+                let odd = n & 1 == 1;
+                let times = if odd { (n / 2) + 1 } else { n / 2 };
+
+                r.loop_.write(|w| unsafe { w.cnt().bits(times) });
+
+                // we can subtract 1 by starting at seq1 instead of seq0
+                if odd {
+                    // tasks_seqstart() doesn't exist in all svds so write its bit instead
+                    r.tasks_seqstart[1].write(|w| unsafe { w.bits(0x01) });
+                } else {
+                    // tasks_seqstart() doesn't exist in all svds so write its bit instead
+                    r.tasks_seqstart[0].write(|w| unsafe { w.bits(0x01) });
+                }
+            }
+            // to play infinitely, repeat the sequence one time, then have loops done self trigger seq0 again
+            SequenceMode::Infinite => {
+                r.loop_.write(|w| unsafe { w.cnt().bits(0x1) });
+                r.shorts.write(|w| w.loopsdone_seqstart0().enabled());
+
+                // tasks_seqstart() doesn't exist in all svds so write its bit instead
+                r.tasks_seqstart[0].write(|w| unsafe { w.bits(0x01) });
+            }
+        }
+
+        Ok(())
+    }
+
+    /// Stop playback.
+    #[inline(always)]
+    pub fn stop(&self) {
+        let r = T::regs();
+
+        r.shorts.reset();
+
+        compiler_fence(Ordering::SeqCst);
+
+        // tasks_stop() doesn't exist in all svds so write its bit instead
+        r.tasks_stop.write(|w| unsafe { w.bits(0x01) });
+    }
+
+    /// Disables the PWM generator.
+    #[inline(always)]
+    pub fn disable(&self) {
+        let r = T::regs();
+        r.enable.write(|w| w.enable().disabled());
+    }
+}
+
+impl<'a, T: Instance> Drop for SequencePwm<'a, T> {
+    fn drop(&mut self) {
+        let r = T::regs();
+
+        self.stop();
+        self.disable();
+
+        if let Some(pin) = &self.ch0 {
+            pin.set_low();
+            pin.conf().write(|w| w);
+            r.psel.out[0].write(|w| unsafe { w.bits(0x80000000) });
+        }
+        if let Some(pin) = &self.ch1 {
+            pin.set_low();
+            pin.conf().write(|w| w);
+            r.psel.out[1].write(|w| unsafe { w.bits(0x80000000) });
+        }
+        if let Some(pin) = &self.ch2 {
+            pin.set_low();
+            pin.conf().write(|w| w);
+            r.psel.out[2].write(|w| unsafe { w.bits(0x80000000) });
+        }
+        if let Some(pin) = &self.ch3 {
+            pin.set_low();
+            pin.conf().write(|w| w);
+            r.psel.out[3].write(|w| unsafe { w.bits(0x80000000) });
+        }
+    }
+}
+
+/// Configure an infinite looping sequence for `SequencePwm`
+#[non_exhaustive]
+pub struct SequenceConfig {
+    /// Selects up mode or up-and-down mode for the counter
+    pub counter_mode: CounterMode,
+    /// Top value to be compared against buffer values
+    pub top: u16,
+    /// Configuration for PWM_CLK
+    pub prescaler: Prescaler,
+    /// How a sequence is read from RAM and is spread to the compare register
+    pub sequence_load: SequenceLoad,
+    /// Number of PWM periods to delay between each sequence sample
+    pub refresh: u32,
+    /// Number of PWM periods after the sequence ends before starting the next sequence
+    pub end_delay: u32,
+}
+
+impl Default for SequenceConfig {
+    fn default() -> SequenceConfig {
+        SequenceConfig {
+            counter_mode: CounterMode::Up,
+            top: 1000,
+            prescaler: Prescaler::Div16,
+            sequence_load: SequenceLoad::Common,
+            refresh: 0,
+            end_delay: 0,
+        }
+    }
+}
+
+/// How many times to run the sequence
+#[derive(Debug, Eq, PartialEq, Clone, Copy)]
+pub enum SequenceMode {
+    /// Run sequence n Times total
+    Times(u16),
+    /// Repeat until `stop` is called.
+    Infinite,
+}
+
+/// PWM Base clock is system clock (16MHz) divided by prescaler
+#[derive(Debug, Eq, PartialEq, Clone, Copy)]
+pub enum Prescaler {
+    Div1,
+    Div2,
+    Div4,
+    Div8,
+    Div16,
+    Div32,
+    Div64,
+    Div128,
+}
+
+/// How the sequence values are distributed across the channels
+#[derive(Debug, Eq, PartialEq, Clone, Copy)]
+pub enum SequenceLoad {
+    /// Provided sequence will be used across all channels
+    Common,
+    /// Provided sequence contains grouped values for each channel ex:
+    /// [ch0_0_and_ch1_0, ch2_0_and_ch3_0, ... ch0_n_and_ch1_n, ch2_n_and_ch3_n]
+    Grouped,
+    /// Provided sequence contains individual values for each channel ex:
+    /// [ch0_0, ch1_0, ch2_0, ch3_0... ch0_n, ch1_n, ch2_n, ch3_n]
+    Individual,
+    /// Similar to Individual mode, but only three channels are used. The fourth
+    /// value is loaded into the pulse generator counter as its top value.
+    Waveform,
+}
+
+/// Selects up mode or up-and-down mode for the counter
+#[derive(Debug, Eq, PartialEq, Clone, Copy)]
+pub enum CounterMode {
+    /// Up counter (edge-aligned PWM duty cycle)
+    Up,
+    /// Up and down counter (center-aligned PWM duty cycle)
+    UpAndDown,
+}
+
+impl<'d, T: Instance> SimplePwm<'d, T> {
+    /// Creates the interface to a `SimplePwm`
+    ///
+    /// Defaults the freq to 1Mhz, max_duty 1000, duty 0, up mode, and pins low.
+    /// Must be started by calling `set_duty`
+    ///
+    /// # Safety
+    ///
+    /// The returned API is safe unless you use `mem::forget` (or similar safe
+    /// mechanisms) on stack allocated buffers which which have been passed to
+    /// [`new()`](SimplePwm::new).
+    #[allow(unused_unsafe)]
+    pub fn new(
+        _pwm: impl Unborrow<Target = T> + 'd,
+        ch0: impl Unborrow<Target = impl GpioOptionalPin> + 'd,
+        ch1: impl Unborrow<Target = impl GpioOptionalPin> + 'd,
+        ch2: impl Unborrow<Target = impl GpioOptionalPin> + 'd,
+        ch3: impl Unborrow<Target = impl GpioOptionalPin> + 'd,
+    ) -> Self {
+        unborrow!(ch0, ch1, ch2, ch3);
+
+        let r = T::regs();
+
+        if let Some(pin) = ch0.pin_mut() {
+            pin.set_low();
+            pin.conf().write(|w| w.dir().output());
+        }
+        if let Some(pin) = ch1.pin_mut() {
+            pin.set_low();
+            pin.conf().write(|w| w.dir().output());
+        }
+        if let Some(pin) = ch2.pin_mut() {
+            pin.set_low();
+            pin.conf().write(|w| w.dir().output());
+        }
+        if let Some(pin) = ch3.pin_mut() {
+            pin.set_low();
+            pin.conf().write(|w| w.dir().output());
+        }
+
+        // if NoPin provided writes disconnected (top bit 1) 0x80000000 else
+        // writes pin number ex 13 (0x0D) which is connected (top bit 0)
+        r.psel.out[0].write(|w| unsafe { w.bits(ch0.psel_bits()) });
+        r.psel.out[1].write(|w| unsafe { w.bits(ch1.psel_bits()) });
+        r.psel.out[2].write(|w| unsafe { w.bits(ch2.psel_bits()) });
+        r.psel.out[3].write(|w| unsafe { w.bits(ch3.psel_bits()) });
+
+        let pwm = Self {
+            phantom: PhantomData,
+            ch0: ch0.degrade_optional(),
+            ch1: ch1.degrade_optional(),
+            ch2: ch2.degrade_optional(),
+            ch3: ch3.degrade_optional(),
+            duty: [0; 4],
+        };
+
+        // Disable all interrupts
+        r.intenclr.write(|w| unsafe { w.bits(0xFFFF_FFFF) });
+        r.shorts.reset();
+
+        // Enable
+        r.enable.write(|w| w.enable().enabled());
+
+        r.seq0
+            .ptr
+            .write(|w| unsafe { w.bits(&pwm.duty as *const _ as u32) });
+
         r.seq0.cnt.write(|w| unsafe { w.bits(4) });
-        r.seq0.refresh.write(|w| unsafe { w.bits(32) });
+        r.seq0.refresh.write(|w| unsafe { w.bits(0) });
         r.seq0.enddelay.write(|w| unsafe { w.bits(0) });
 
         r.decoder.write(|w| {
@@ -89,14 +407,24 @@ impl<'d, T: Instance> Pwm<'d, T> {
             w.mode().refresh_count()
         });
         r.mode.write(|w| w.updown().up());
-        r.prescaler.write(|w| w.prescaler().div_1());
+        r.prescaler.write(|w| w.prescaler().div_16());
-        r.countertop
+        r.countertop.write(|w| unsafe { w.countertop().bits(1000) });
-            .write(|w| unsafe { w.countertop().bits(32767) });
         r.loop_.write(|w| w.cnt().disabled());
 
-        Self {
+        pwm
-            phantom: PhantomData,
     }
+
+    /// Stop playback
+    #[inline(always)]
+    pub fn stop(&self) {
+        let r = T::regs();
+
+        r.shorts.reset();
+
+        compiler_fence(Ordering::SeqCst);
+
+        // tasks_stop() doesn't exist in all svds so write its bit instead
+        r.tasks_stop.write(|w| unsafe { w.bits(0x01) });
     }
 
     /// Enables the PWM generator.
@@ -114,12 +442,24 @@ impl<'d, T: Instance> Pwm<'d, T> {
     }
 
     /// Sets duty cycle (15 bit) for a PWM channel.
-    pub fn set_duty(&self, channel: usize, duty: u16) {
+    pub fn set_duty(&mut self, channel: usize, duty: u16) {
-        let s = T::state();
+        let r = T::regs();
-        unsafe { (*s.duty.get())[channel] = duty & 0x7FFF };
 
+        self.duty[channel] = duty & 0x7FFF;
+
+        r.seq0
+            .ptr
+            .write(|w| unsafe { w.bits(&self.duty as *const _ as u32) });
+
+        // defensive before seqstart
         compiler_fence(Ordering::SeqCst);
-        T::regs().tasks_seqstart[0].write(|w| unsafe { w.bits(1) });
+
+        // tasks_seqstart() doesn't exist in all svds so write its bit instead
+        r.tasks_seqstart[0].write(|w| unsafe { w.bits(1) });
+
+        // defensive wait until waveform is loaded after seqstart
+        while r.events_seqend[0].read().bits() == 0 {}
+        r.events_seqend[0].write(|w| w);
     }
 
     /// Sets the PWM clock prescaler.
@@ -128,7 +468,7 @@ impl<'d, T: Instance> Pwm<'d, T> {
         T::regs().prescaler.write(|w| w.prescaler().bits(div as u8));
     }
 
-    /// Sets the PWM clock prescaler.
+    /// Gets the PWM clock prescaler.
     #[inline(always)]
     pub fn prescaler(&self) -> Prescaler {
         match T::regs().prescaler.read().prescaler().bits() {
@@ -175,36 +515,41 @@ impl<'d, T: Instance> Pwm<'d, T> {
     }
 }
 
-impl<'a, T: Instance> Drop for Pwm<'a, T> {
+impl<'a, T: Instance> Drop for SimplePwm<'a, T> {
     fn drop(&mut self) {
         let r = T::regs();
-        r.enable.write(|w| w.enable().disabled());
 
-        info!("pwm drop: done");
+        self.stop();
+        self.disable();
 
-        // TODO: disable pins
+        if let Some(pin) = &self.ch0 {
+            pin.set_low();
+            pin.conf().write(|w| w);
+            r.psel.out[0].write(|w| unsafe { w.bits(0x80000000) });
+        }
+        if let Some(pin) = &self.ch1 {
+            pin.set_low();
+            pin.conf().write(|w| w);
+            r.psel.out[1].write(|w| unsafe { w.bits(0x80000000) });
+        }
+        if let Some(pin) = &self.ch2 {
+            pin.set_low();
+            pin.conf().write(|w| w);
+            r.psel.out[2].write(|w| unsafe { w.bits(0x80000000) });
+        }
+        if let Some(pin) = &self.ch3 {
+            pin.set_low();
+            pin.conf().write(|w| w);
+            r.psel.out[3].write(|w| unsafe { w.bits(0x80000000) });
+        }
     }
 }
 
 pub(crate) mod sealed {
     use super::*;
 
-    pub struct State {
-        pub duty: UnsafeCell<[u16; 4]>,
-    }
-    unsafe impl Sync for State {}
-
-    impl State {
-        pub const fn new() -> Self {
-            Self {
-                duty: UnsafeCell::new([0; 4]),
-            }
-        }
-    }
-
     pub trait Instance {
         fn regs() -> &'static pac::pwm0::RegisterBlock;
-        fn state() -> &'static State;
     }
 }
 
@@ -218,10 +563,6 @@ macro_rules! impl_pwm {
             fn regs() -> &'static pac::pwm0::RegisterBlock {
                 unsafe { &*pac::$pac_type::ptr() }
             }
-            fn state() -> &'static crate::pwm::sealed::State {
-                static STATE: crate::pwm::sealed::State = crate::pwm::sealed::State::new();
-                &STATE
-            }
         }
         impl crate::pwm::Instance for peripherals::$type {
             type Interrupt = crate::interrupt::$irq;

embassy-nrf/src/util.rs

@@ -2,15 +2,15 @@ const SRAM_LOWER: usize = 0x2000_0000;
 const SRAM_UPPER: usize = 0x3000_0000;
 
 /// Does this slice reside entirely within RAM?
-pub(crate) fn slice_in_ram(slice: &[u8]) -> bool {
+pub(crate) fn slice_in_ram<T>(slice: &[T]) -> bool {
     let ptr = slice.as_ptr() as usize;
-    ptr >= SRAM_LOWER && (ptr + slice.len()) < SRAM_UPPER
+    ptr >= SRAM_LOWER && (ptr + slice.len() * core::mem::size_of::<T>()) < SRAM_UPPER
 }
 
 /// Return an error if slice is not in RAM.
 #[cfg(not(feature = "nrf51"))]
-pub(crate) fn slice_in_ram_or<T>(slice: &[u8], err: T) -> Result<(), T> {
+pub(crate) fn slice_in_ram_or<T, E>(slice: &[T], err: E) -> Result<(), E> {
-    if slice.len() == 0 || slice_in_ram(slice) {
+    if slice.is_empty() || slice_in_ram(slice) {
         Ok(())
     } else {
         Err(err)

examples/nrf/src/bin/pwm.rs

@@ -7,7 +7,7 @@ mod example_common;
 use defmt::*;
 use embassy::executor::Spawner;
 use embassy::time::{Duration, Timer};
-use embassy_nrf::pwm::{Prescaler, Pwm};
+use embassy_nrf::pwm::{Prescaler, SimplePwm};
 use embassy_nrf::Peripherals;
 
 // for i in range(1024): print(int((math.sin(i/512*math.pi)*0.4+0.5)**2*32767), ', ', end='')
@@ -85,8 +85,9 @@ static DUTY: [u16; 1024] = [
 
 #[embassy::main]
 async fn main(_spawner: Spawner, p: Peripherals) {
-    let pwm = Pwm::new(p.PWM0, p.P0_13, p.P0_14, p.P0_16, p.P0_15);
+    let mut pwm = SimplePwm::new(p.PWM0, p.P0_13, p.P0_14, p.P0_16, p.P0_15);
     pwm.set_prescaler(Prescaler::Div1);
+    pwm.set_max_duty(32767);
     info!("pwm initialized!");
 
     let mut i = 0;

examples/nrf/src/bin/pwm_led.rs

@@ -0,0 +1,47 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+#[path = "../example_common.rs"]
+mod example_common;
+use defmt::*;
+use embassy::executor::Spawner;
+use embassy::time::{Duration, Timer};
+use embassy_nrf::gpio::NoPin;
+use embassy_nrf::pwm::{Prescaler, SimplePwm};
+use embassy_nrf::Peripherals;
+
+#[embassy::main]
+async fn main(_spawner: Spawner, p: Peripherals) {
+    let mut pwm = SimplePwm::new(p.PWM0, p.P0_13, NoPin, NoPin, NoPin);
+    // set_period doesnt actually set what you give it, because it only has a
+    // few options from the hardhware so be explicit instead
+    // Div128 is slowest, 125khz still crazy fast for our eyes
+    pwm.set_prescaler(Prescaler::Div128);
+
+    info!("pwm initialized!");
+
+    // default max_duty if not specified is 1000
+    // so 0 would be fully off and 1000 or above would be fully on
+    loop {
+        info!("100%");
+        pwm.set_duty(0, 1000);
+        Timer::after(Duration::from_millis(5000)).await;
+
+        info!("25%");
+        pwm.set_duty(0, 250);
+        Timer::after(Duration::from_millis(5000)).await;
+
+        info!("10%");
+        pwm.set_duty(0, 100);
+        Timer::after(Duration::from_millis(5000)).await;
+
+        info!("5%");
+        pwm.set_duty(0, 50);
+        Timer::after(Duration::from_millis(5000)).await;
+
+        info!("0%");
+        pwm.set_duty(0, 0);
+        Timer::after(Duration::from_millis(5000)).await;
+    }
+}

examples/nrf/src/bin/pwm_sequence.rs

@@ -0,0 +1,115 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+#[path = "../example_common.rs"]
+mod example_common;
+use defmt::*;
+use embassy::executor::Spawner;
+use embassy::time::{Duration, Timer};
+use embassy_nrf::gpio::NoPin;
+use embassy_nrf::pwm::{Prescaler, SequenceConfig, SequenceMode, SequencePwm};
+use embassy_nrf::Peripherals;
+
+#[embassy::main]
+async fn main(_spawner: Spawner, p: Peripherals) {
+    // for i in range(1024): print(int((math.sin(i/512*math.pi)*0.4+0.5)**2*32767), ', ', end='')
+    let seq_values: [u16; 1024] = [
+        8191, 8272, 8353, 8434, 8516, 8598, 8681, 8764, 8847, 8931, 9015, 9099, 9184, 9269, 9354,
+        9440, 9526, 9613, 9700, 9787, 9874, 9962, 10050, 10139, 10227, 10316, 10406, 10495, 10585,
+        10675, 10766, 10857, 10948, 11039, 11131, 11223, 11315, 11407, 11500, 11592, 11685, 11779,
+        11872, 11966, 12060, 12154, 12248, 12343, 12438, 12533, 12628, 12723, 12818, 12914, 13010,
+        13106, 13202, 13298, 13394, 13491, 13587, 13684, 13781, 13878, 13975, 14072, 14169, 14266,
+        14364, 14461, 14558, 14656, 14754, 14851, 14949, 15046, 15144, 15242, 15339, 15437, 15535,
+        15632, 15730, 15828, 15925, 16023, 16120, 16218, 16315, 16412, 16510, 16607, 16704, 16801,
+        16898, 16995, 17091, 17188, 17284, 17380, 17477, 17572, 17668, 17764, 17859, 17955, 18050,
+        18145, 18239, 18334, 18428, 18522, 18616, 18710, 18803, 18896, 18989, 19082, 19174, 19266,
+        19358, 19449, 19540, 19631, 19722, 19812, 19902, 19991, 20081, 20169, 20258, 20346, 20434,
+        20521, 20608, 20695, 20781, 20867, 20952, 21037, 21122, 21206, 21290, 21373, 21456, 21538,
+        21620, 21701, 21782, 21863, 21943, 22022, 22101, 22179, 22257, 22335, 22412, 22488, 22564,
+        22639, 22714, 22788, 22861, 22934, 23007, 23079, 23150, 23220, 23290, 23360, 23429, 23497,
+        23564, 23631, 23698, 23763, 23828, 23892, 23956, 24019, 24081, 24143, 24204, 24264, 24324,
+        24383, 24441, 24499, 24555, 24611, 24667, 24721, 24775, 24828, 24881, 24933, 24983, 25034,
+        25083, 25132, 25180, 25227, 25273, 25319, 25363, 25407, 25451, 25493, 25535, 25575, 25615,
+        25655, 25693, 25731, 25767, 25803, 25838, 25873, 25906, 25939, 25971, 26002, 26032, 26061,
+        26089, 26117, 26144, 26170, 26195, 26219, 26242, 26264, 26286, 26307, 26327, 26346, 26364,
+        26381, 26397, 26413, 26427, 26441, 26454, 26466, 26477, 26487, 26496, 26505, 26512, 26519,
+        26525, 26530, 26534, 26537, 26539, 26540, 26541, 26540, 26539, 26537, 26534, 26530, 26525,
+        26519, 26512, 26505, 26496, 26487, 26477, 26466, 26454, 26441, 26427, 26413, 26397, 26381,
+        26364, 26346, 26327, 26307, 26286, 26264, 26242, 26219, 26195, 26170, 26144, 26117, 26089,
+        26061, 26032, 26002, 25971, 25939, 25906, 25873, 25838, 25803, 25767, 25731, 25693, 25655,
+        25615, 25575, 25535, 25493, 25451, 25407, 25363, 25319, 25273, 25227, 25180, 25132, 25083,
+        25034, 24983, 24933, 24881, 24828, 24775, 24721, 24667, 24611, 24555, 24499, 24441, 24383,
+        24324, 24264, 24204, 24143, 24081, 24019, 23956, 23892, 23828, 23763, 23698, 23631, 23564,
+        23497, 23429, 23360, 23290, 23220, 23150, 23079, 23007, 22934, 22861, 22788, 22714, 22639,
+        22564, 22488, 22412, 22335, 22257, 22179, 22101, 22022, 21943, 21863, 21782, 21701, 21620,
+        21538, 21456, 21373, 21290, 21206, 21122, 21037, 20952, 20867, 20781, 20695, 20608, 20521,
+        20434, 20346, 20258, 20169, 20081, 19991, 19902, 19812, 19722, 19631, 19540, 19449, 19358,
+        19266, 19174, 19082, 18989, 18896, 18803, 18710, 18616, 18522, 18428, 18334, 18239, 18145,
+        18050, 17955, 17859, 17764, 17668, 17572, 17477, 17380, 17284, 17188, 17091, 16995, 16898,
+        16801, 16704, 16607, 16510, 16412, 16315, 16218, 16120, 16023, 15925, 15828, 15730, 15632,
+        15535, 15437, 15339, 15242, 15144, 15046, 14949, 14851, 14754, 14656, 14558, 14461, 14364,
+        14266, 14169, 14072, 13975, 13878, 13781, 13684, 13587, 13491, 13394, 13298, 13202, 13106,
+        13010, 12914, 12818, 12723, 12628, 12533, 12438, 12343, 12248, 12154, 12060, 11966, 11872,
+        11779, 11685, 11592, 11500, 11407, 11315, 11223, 11131, 11039, 10948, 10857, 10766, 10675,
+        10585, 10495, 10406, 10316, 10227, 10139, 10050, 9962, 9874, 9787, 9700, 9613, 9526, 9440,
+        9354, 9269, 9184, 9099, 9015, 8931, 8847, 8764, 8681, 8598, 8516, 8434, 8353, 8272, 8191,
+        8111, 8031, 7952, 7873, 7794, 7716, 7638, 7561, 7484, 7407, 7331, 7255, 7180, 7105, 7031,
+        6957, 6883, 6810, 6738, 6665, 6594, 6522, 6451, 6381, 6311, 6241, 6172, 6104, 6036, 5968,
+        5901, 5834, 5767, 5702, 5636, 5571, 5507, 5443, 5379, 5316, 5253, 5191, 5130, 5068, 5008,
+        4947, 4888, 4828, 4769, 4711, 4653, 4596, 4539, 4482, 4426, 4371, 4316, 4261, 4207, 4153,
+        4100, 4047, 3995, 3943, 3892, 3841, 3791, 3741, 3691, 3642, 3594, 3546, 3498, 3451, 3404,
+        3358, 3312, 3267, 3222, 3178, 3134, 3090, 3047, 3005, 2962, 2921, 2879, 2839, 2798, 2758,
+        2719, 2680, 2641, 2603, 2565, 2528, 2491, 2454, 2418, 2382, 2347, 2312, 2278, 2244, 2210,
+        2177, 2144, 2112, 2080, 2048, 2017, 1986, 1956, 1926, 1896, 1867, 1838, 1810, 1781, 1754,
+        1726, 1699, 1673, 1646, 1620, 1595, 1570, 1545, 1520, 1496, 1472, 1449, 1426, 1403, 1380,
+        1358, 1336, 1315, 1294, 1273, 1252, 1232, 1212, 1192, 1173, 1154, 1135, 1117, 1099, 1081,
+        1063, 1046, 1029, 1012, 996, 980, 964, 948, 933, 918, 903, 888, 874, 860, 846, 833, 819,
+        806, 793, 781, 768, 756, 744, 733, 721, 710, 699, 688, 677, 667, 657, 647, 637, 627, 618,
+        609, 599, 591, 582, 574, 565, 557, 549, 541, 534, 526, 519, 512, 505, 498, 492, 485, 479,
+        473, 467, 461, 455, 450, 444, 439, 434, 429, 424, 419, 415, 410, 406, 402, 398, 394, 390,
+        386, 383, 379, 376, 373, 370, 367, 364, 361, 359, 356, 354, 351, 349, 347, 345, 343, 342,
+        340, 338, 337, 336, 334, 333, 332, 331, 330, 330, 329, 328, 328, 328, 327, 327, 327, 327,
+        327, 328, 328, 328, 329, 330, 330, 331, 332, 333, 334, 336, 337, 338, 340, 342, 343, 345,
+        347, 349, 351, 354, 356, 359, 361, 364, 367, 370, 373, 376, 379, 383, 386, 390, 394, 398,
+        402, 406, 410, 415, 419, 424, 429, 434, 439, 444, 450, 455, 461, 467, 473, 479, 485, 492,
+        498, 505, 512, 519, 526, 534, 541, 549, 557, 565, 574, 582, 591, 599, 609, 618, 627, 637,
+        647, 657, 667, 677, 688, 699, 710, 721, 733, 744, 756, 768, 781, 793, 806, 819, 833, 846,
+        860, 874, 888, 903, 918, 933, 948, 964, 980, 996, 1012, 1029, 1046, 1063, 1081, 1099, 1117,
+        1135, 1154, 1173, 1192, 1212, 1232, 1252, 1273, 1294, 1315, 1336, 1358, 1380, 1403, 1426,
+        1449, 1472, 1496, 1520, 1545, 1570, 1595, 1620, 1646, 1673, 1699, 1726, 1754, 1781, 1810,
+        1838, 1867, 1896, 1926, 1956, 1986, 2017, 2048, 2080, 2112, 2144, 2177, 2210, 2244, 2278,
+        2312, 2347, 2382, 2418, 2454, 2491, 2528, 2565, 2603, 2641, 2680, 2719, 2758, 2798, 2839,
+        2879, 2921, 2962, 3005, 3047, 3090, 3134, 3178, 3222, 3267, 3312, 3358, 3404, 3451, 3498,
+        3546, 3594, 3642, 3691, 3741, 3791, 3841, 3892, 3943, 3995, 4047, 4100, 4153, 4207, 4261,
+        4316, 4371, 4426, 4482, 4539, 4596, 4653, 4711, 4769, 4828, 4888, 4947, 5008, 5068, 5130,
+        5191, 5253, 5316, 5379, 5443, 5507, 5571, 5636, 5702, 5767, 5834, 5901, 5968, 6036, 6104,
+        6172, 6241, 6311, 6381, 6451, 6522, 6594, 6665, 6738, 6810, 6883, 6957, 7031, 7105, 7180,
+        7255, 7331, 7407, 7484, 7561, 7638, 7716, 7794, 7873, 7952, 8031, 8111,
+    ];
+
+    let mut config = SequenceConfig::default();
+    config.prescaler = Prescaler::Div1;
+    // 1 period is 32767 * 1/16mhz = 0.002047938 = 2.047938ms
+    config.top = 32767;
+    // pwm example is delaying >~3ms before updating duty cycle, our refreshes
+    // happen exactly at 2.047938ms so we need a delay after each value of >~1ms
+    // which for us is ~1-2 periods
+    config.refresh = 3;
+
+    let pwm = unwrap!(SequencePwm::new(
+        p.PWM0,
+        p.P0_13,
+        NoPin,
+        NoPin,
+        NoPin,
+        config,
+        &seq_values
+    ));
+    let _ = pwm.start(SequenceMode::Infinite);
+    info!("pwm started!");
+
+    loop {
+        Timer::after(Duration::from_millis(1000)).await;
+    }
+}

examples/nrf/src/bin/pwm_servo.rs

@@ -0,0 +1,48 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+#[path = "../example_common.rs"]
+mod example_common;
+use defmt::*;
+use embassy::executor::Spawner;
+use embassy::time::{Duration, Timer};
+use embassy_nrf::gpio::NoPin;
+use embassy_nrf::pwm::{Prescaler, SimplePwm};
+use embassy_nrf::Peripherals;
+
+#[embassy::main]
+async fn main(_spawner: Spawner, p: Peripherals) {
+    let mut pwm = SimplePwm::new(p.PWM0, p.P0_05, NoPin, NoPin, NoPin);
+    // sg90 microervo requires 50hz or 20ms period
+    // set_period can only set down to 125khz so we cant use it directly
+    // Div128 is 125khz or 0.000008s or 0.008ms, 20/0.008 is 2500 is top
+    pwm.set_prescaler(Prescaler::Div128);
+    pwm.set_max_duty(2500);
+    info!("pwm initialized!");
+
+    Timer::after(Duration::from_millis(5000)).await;
+
+    // 1ms 0deg (1/.008=125), 1.5ms 90deg (1.5/.008=187.5), 2ms 180deg (2/.008=250),
+    loop {
+        info!("45 deg");
+        pwm.set_duty(0, 2500 - 156);
+        Timer::after(Duration::from_millis(5000)).await;
+
+        info!("90 deg");
+        pwm.set_duty(0, 2500 - 187);
+        Timer::after(Duration::from_millis(5000)).await;
+
+        info!("135 deg");
+        pwm.set_duty(0, 2500 - 218);
+        Timer::after(Duration::from_millis(5000)).await;
+
+        info!("180 deg");
+        pwm.set_duty(0, 2500 - 250);
+        Timer::after(Duration::from_millis(5000)).await;
+
+        info!("0 deg");
+        pwm.set_duty(0, 2500 - 125);
+        Timer::after(Duration::from_millis(5000)).await;
+    }
+}