1 files changed, 169 insertions, 0 deletions

diff --git a/embassy-stm32/src/timer/ringbuffered.rs b/embassy-stm32/src/timer/ringbuffered.rs
new file mode 100644
index 000000000..e8f97bf59
--- /dev/null
+++ b/embassy-stm32/src/timer/ringbuffered.rs
@@ -0,0 +1,169 @@
+//! RingBuffered PWM driver.
+
+use core::mem::ManuallyDrop;
+use core::task::Waker;
+
+use super::low_level::Timer;
+use super::{Channel, GeneralInstance4Channel};
+use crate::dma::WritableRingBuffer;
+use crate::dma::ringbuffer::Error;
+
+/// A PWM channel that uses a DMA ring buffer for continuous waveform generation.
+///
+/// This allows you to continuously update PWM duty cycles via DMA without blocking the CPU.
+/// The ring buffer enables smooth, uninterrupted waveform generation by automatically cycling
+/// through duty cycle values stored in memory.
+///
+/// You can write new duty cycle values to the ring buffer while it's running, enabling
+/// dynamic waveform generation for applications like motor control, LED dimming, or audio output.
+///
+/// # Example
+/// ```ignore
+/// let mut channel = pwm.ch1().into_ring_buffered_channel(dma_ch, &mut buffer);
+/// channel.start(); // Start DMA transfer
+/// channel.write(&[100, 200, 300]).ok(); // Update duty cycles
+/// ```
+pub struct RingBufferedPwmChannel<'d, T: GeneralInstance4Channel> {
+    timer: ManuallyDrop<Timer<'d, T>>,
+    ring_buf: WritableRingBuffer<'d, u16>,
+    channel: Channel,
+}
+
+impl<'d, T: GeneralInstance4Channel> RingBufferedPwmChannel<'d, T> {
+    pub(crate) fn new(
+        timer: ManuallyDrop<Timer<'d, T>>,
+        channel: Channel,
+        ring_buf: WritableRingBuffer<'d, u16>,
+    ) -> Self {
+        Self {
+            timer,
+            ring_buf,
+            channel,
+        }
+    }
+
+    /// Start the ring buffer operation.
+    ///
+    /// You must call this after creating it for it to work.
+    pub fn start(&mut self) {
+        self.ring_buf.start()
+    }
+
+    /// Clear all data in the ring buffer.
+    pub fn clear(&mut self) {
+        self.ring_buf.clear()
+    }
+
+    /// Write elements directly to the raw buffer. This can be used to fill the buffer before starting the DMA transfer.
+    pub fn write_immediate(&mut self, buf: &[u16]) -> Result<(usize, usize), Error> {
+        self.ring_buf.write_immediate(buf)
+    }
+
+    /// Write elements from the ring buffer
+    /// Return a tuple of the length written and the length remaining in the buffer
+    pub fn write(&mut self, buf: &[u16]) -> Result<(usize, usize), Error> {
+        self.ring_buf.write(buf)
+    }
+
+    /// Write an exact number of elements to the ringbuffer.
+    pub async fn write_exact(&mut self, buffer: &[u16]) -> Result<usize, Error> {
+        self.ring_buf.write_exact(buffer).await
+    }
+
+    /// Wait for any ring buffer write error.
+    pub async fn wait_write_error(&mut self) -> Result<usize, Error> {
+        self.ring_buf.wait_write_error().await
+    }
+
+    /// The current length of the ringbuffer
+    pub fn len(&mut self) -> Result<usize, Error> {
+        self.ring_buf.len()
+    }
+
+    /// The capacity of the ringbuffer
+    pub const fn capacity(&self) -> usize {
+        self.ring_buf.capacity()
+    }
+
+    /// Set a waker to be woken when at least one byte is send.
+    pub fn set_waker(&mut self, waker: &Waker) {
+        self.ring_buf.set_waker(waker)
+    }
+
+    /// Request the DMA to reset. The configuration for this channel will not be preserved.
+    ///
+    /// This doesn't immediately stop the transfer, you have to wait until is_running returns false.
+    pub fn request_reset(&mut self) {
+        self.ring_buf.request_reset()
+    }
+
+    /// Request the transfer to pause, keeping the existing configuration for this channel.
+    /// To restart the transfer, call [`start`](Self::start) again.
+    ///
+    /// This doesn't immediately stop the transfer, you have to wait until is_running returns false.
+    pub fn request_pause(&mut self) {
+        self.ring_buf.request_pause()
+    }
+
+    /// Return whether DMA is still running.
+    ///
+    /// If this returns false, it can be because either the transfer finished, or it was requested to stop early with request_stop.
+    pub fn is_running(&mut self) -> bool {
+        self.ring_buf.is_running()
+    }
+
+    /// Stop the DMA transfer and await until the buffer is empty.
+    ///
+    /// This disables the DMA transfer's circular mode so that the transfer stops when all available data has been written.
+    ///
+    /// This is designed to be used with streaming output data such as the I2S/SAI or DAC.
+    pub async fn stop(&mut self) {
+        self.ring_buf.stop().await
+    }
+
+    /// Enable the given channel.
+    pub fn enable(&mut self) {
+        self.timer.enable_channel(self.channel, true);
+    }
+
+    /// Disable the given channel.
+    pub fn disable(&mut self) {
+        self.timer.enable_channel(self.channel, false);
+    }
+
+    /// Check whether given channel is enabled
+    pub fn is_enabled(&self) -> bool {
+        self.timer.get_channel_enable_state(self.channel)
+    }
+
+    /// Get max duty value.
+    ///
+    /// This value depends on the configured frequency and the timer's clock rate from RCC.
+    pub fn max_duty_cycle(&self) -> u16 {
+        let max = self.timer.get_max_compare_value();
+        assert!(max < u16::MAX as u32);
+        max as u16 + 1
+    }
+
+    /// Set the output polarity for a given channel.
+    pub fn set_polarity(&mut self, polarity: super::low_level::OutputPolarity) {
+        self.timer.set_output_polarity(self.channel, polarity);
+    }
+
+    /// Set the output compare mode for a given channel.
+    pub fn set_output_compare_mode(&mut self, mode: super::low_level::OutputCompareMode) {
+        self.timer.set_output_compare_mode(self.channel, mode);
+    }
+}
+
+/// A group of four [`SimplePwmChannel`]s, obtained from [`SimplePwm::split`].
+pub struct RingBufferedPwmChannels<'d, T: GeneralInstance4Channel> {
+    /// Channel 1
+    pub ch1: RingBufferedPwmChannel<'d, T>,
+    /// Channel 2
+    pub ch2: RingBufferedPwmChannel<'d, T>,
+    /// Channel 3
+    pub ch3: RingBufferedPwmChannel<'d, T>,
+    /// Channel 4
+    pub ch4: RingBufferedPwmChannel<'d, T>,
+}