[embassy-stm32] add DMA-based input capture for timer channels

embassy-stm32/CHANGELOG.md

@@ -7,7 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 <!-- next-header -->
 ## Unreleased - ReleaseDate
-
+- Add `receive_waveform` method in `InputCapture`, allowing asynchronous input capture with DMA.
 - fix: Fixed STM32H5 builds requiring time feature
 - feat: Derive Clone, Copy for QSPI Config
 - fix: stm32/i2c in master mode (blocking): subsequent transmissions failed after a NACK was received

embassy-stm32/src/timer/input_capture.rs

@@ -155,6 +155,48 @@ impl<'d, T: GeneralInstance4Channel> InputCapture<'d, T> {
         self.new_future(channel, InputCaptureMode::BothEdges, InputTISelection::Alternate)
             .await
     }
+
+    /// Capture a sequence of timer input edges into a buffer using DMA
+    pub async fn receive_waveform<M>(&mut self, dma: Peri<'_, impl super::Dma<T, M>>, buf: &mut [u16])
+    where
+        M: TimerChannel,
+    {
+        #[allow(clippy::let_unit_value)] // eg. stm32f334
+        let req = dma.request();
+
+        let original_enable_state = self.is_enabled(M::CHANNEL);
+        let original_cc_dma_enable_state = self.inner.get_cc_dma_enable_state(M::CHANNEL);
+
+        self.inner.set_input_ti_selection(M::CHANNEL, InputTISelection::Normal);
+        self.inner
+            .set_input_capture_mode(M::CHANNEL, InputCaptureMode::BothEdges);
+
+        if !original_cc_dma_enable_state {
+            self.inner.set_cc_dma_enable_state(M::CHANNEL, true);
+        }
+
+        if !original_enable_state {
+            self.enable(M::CHANNEL);
+        }
+
+        unsafe {
+            use crate::dma::{Transfer, TransferOptions};
+
+            Transfer::new_read(
+                dma,
+                req,
+                self.inner.regs_gp16().ccr(M::CHANNEL.index()).as_ptr() as *mut u16,
+                buf,
+                TransferOptions::default(),
+            )
+            .await
+        };
+
+        // restore output compare state
+        if !original_enable_state {
+            self.disable(M::CHANNEL);
+        }
+    }
 }
 
 #[must_use = "futures do nothing unless you `.await` or poll them"]