Optimization to be able to work with only 2 buffers

embassy-nrf/src/i2s.rs

@@ -398,6 +398,7 @@ impl<'d, T: Instance> I2S<'d, T> {
     ) -> FullDuplexStream<'d, T> {
         self.sdout = Some(sdout.into_ref().map_into());
         self.sdin = Some(sdin.into_ref().map_into());
+
         FullDuplexStream { _p: self.build() }
     }
 
@@ -549,6 +550,16 @@ impl<'d, T: Instance> I2S<'d, T> {
 
         let device = Device::<T>::new();
 
+        device.update_tx(buffer_ptr)?;
+
+        Self::wait_tx_ptr_update().await;
+
+        compiler_fence(Ordering::SeqCst);
+
+        Ok(())
+    }
+
+    async fn wait_tx_ptr_update() {
         let drop = OnDrop::new(move || {
             trace!("TX DROP: Stopping");
 
@@ -566,6 +577,7 @@ impl<'d, T: Instance> I2S<'d, T> {
         poll_fn(|cx| {
             T::state().tx_waker.register(cx.waker());
 
+            let device = Device::<T>::new();
             if device.is_tx_ptr_updated() {
                 trace!("TX POLL: Ready");
                 device.reset_tx_ptr_event();
@@ -578,12 +590,7 @@ impl<'d, T: Instance> I2S<'d, T> {
         })
         .await;
 
-        device.update_tx(buffer_ptr)?;
-
-        compiler_fence(Ordering::SeqCst);
         drop.defuse();
-
-        Ok(())
     }
 
     async fn receive_from_ram<S>(buffer_ptr: *mut [S]) -> Result<(), Error>
@@ -599,6 +606,16 @@ impl<'d, T: Instance> I2S<'d, T> {
 
         let device = Device::<T>::new();
 
+        device.update_rx(buffer_ptr)?;
+
+        Self::wait_rx_ptr_update().await;
+
+        compiler_fence(Ordering::SeqCst);
+
+        Ok(())
+    }
+
+    async fn wait_rx_ptr_update() {
         let drop = OnDrop::new(move || {
             trace!("RX DROP: Stopping");
 
@@ -616,6 +633,7 @@ impl<'d, T: Instance> I2S<'d, T> {
         poll_fn(|cx| {
             T::state().rx_waker.register(cx.waker());
 
+            let device = Device::<T>::new();
             if device.is_rx_ptr_updated() {
                 trace!("RX POLL: Ready");
                 device.reset_rx_ptr_event();
@@ -628,13 +646,7 @@ impl<'d, T: Instance> I2S<'d, T> {
         })
         .await;
 
-        device.update_rx(buffer_ptr)?;
-
-        compiler_fence(Ordering::SeqCst);
-
         drop.defuse();
-
-        Ok(())
     }
 }
 
@@ -666,6 +678,8 @@ impl<'d, T: Instance> OutputStream<'d, T> {
 
         device.start();
 
+        I2S::<T>::wait_tx_ptr_update().await;
+
         Ok(())
     }
 
@@ -716,6 +730,8 @@ impl<'d, T: Instance> InputStream<'d, T> {
 
         device.start();
 
+        I2S::<T>::wait_rx_ptr_update().await;
+
         Ok(())
     }
 
@@ -746,7 +762,7 @@ pub struct FullDuplexStream<'d, T: Instance> {
 impl<'d, T: Instance> FullDuplexStream<'d, T> {
     /// Prepare the initial buffers and start the I2S transfer.
     #[allow(unused_mut)]
-    pub async fn start<S>(&mut self, buffer_out: &[S], buffer_in: &mut [S]) -> Result<(), Error>
+    pub async fn start<S>(&mut self, buffer_in: &mut [S], buffer_out: &[S]) -> Result<(), Error>
     where
         S: Sample,
     {
@@ -768,6 +784,9 @@ impl<'d, T: Instance> FullDuplexStream<'d, T> {
 
         device.start();
 
+        I2S::<T>::wait_tx_ptr_update().await;
+        I2S::<T>::wait_rx_ptr_update().await;
+
         Ok(())
     }
 
@@ -782,7 +801,7 @@ impl<'d, T: Instance> FullDuplexStream<'d, T> {
     /// The buffers must not be written/read while being used by the DMA,
     /// which takes two other `send_and_receive` operations being awaited.
     #[allow(unused_mut)]
-    pub async fn send_and_receive_from_ram<S>(&mut self, buffer_out: &[S], buffer_in: &mut [S]) -> Result<(), Error>
+    pub async fn send_and_receive_from_ram<S>(&mut self, buffer_in: &mut [S], buffer_out: &[S]) -> Result<(), Error>
     where
         S: Sample,
     {
@@ -903,7 +922,7 @@ impl<T: Instance> Device<T> {
     #[inline(always)]
     fn enable_rx_ptr_interrupt(&self) {
         trace!("RX PTR INTERRUPT: Enabled");
-        self.0.intenclr.write(|w| w.rxptrupd().clear());
+        self.0.intenset.write(|w| w.rxptrupd().set());
     }
 
     #[inline(always)]
@@ -974,6 +993,7 @@ impl Sample for i32 {
 }
 
 /// A 4-bytes aligned [Buffer].
+#[derive(Clone, Copy)]
 #[repr(align(4))]
 pub struct AlignedBuffer<T: Sample, const N: usize>([T; N]);
 

examples/nrf/src/bin/i2s_waveform.rs

@@ -12,7 +12,8 @@ use {defmt_rtt as _, panic_probe as _};
 
 type Sample = i16;
 
-const NUM_SAMPLES: usize = 6000;
+const NUM_BUFFERS: usize = 2;
+const NUM_SAMPLES: usize = 50;
 
 #[embassy_executor::main]
 async fn main(_spawner: Spawner) {
@@ -30,31 +31,27 @@ async fn main(_spawner: Spawner) {
     let irq = interrupt::take!(I2S);
     let mut output_stream = I2S::master(p.I2S, irq, p.P0_25, p.P0_26, p.P0_27, master_clock, config).output(p.P0_28);
 
-    let mut buffers: [i2s::AlignedBuffer<Sample, NUM_SAMPLES>; 3] = [
+    let mut buffers: [i2s::AlignedBuffer<Sample, NUM_SAMPLES>; NUM_BUFFERS] =
-        i2s::AlignedBuffer::default(),
+        [i2s::AlignedBuffer::default(); NUM_BUFFERS];
-        i2s::AlignedBuffer::default(),
-        i2s::AlignedBuffer::default(),
-    ];
 
     let mut waveform = Waveform::new(1.0 / sample_rate as f32);
 
     waveform.process(&mut buffers[0]);
-    waveform.process(&mut buffers[1]);
 
     output_stream.start(&buffers[0]).await.expect("I2S Start");
 
     let mut index = 1;
     loop {
+        waveform.process(&mut buffers[index]);
+
         if let Err(err) = output_stream.send_from_ram(&buffers[index]).await {
             error!("{}", err);
         }
 
         index += 1;
-        if index >= 3 {
+        if index >= NUM_BUFFERS {
             index = 0;
         }
-
-        waveform.process(&mut buffers[index]);
     }
 }
 
@@ -67,7 +64,8 @@ struct Waveform {
 
 impl Waveform {
     fn new(inv_sample_rate: f32) -> Self {
-        let carrier = SineOsc::new();
+        let mut carrier = SineOsc::new();
+        carrier.set_frequency(110.0, inv_sample_rate);
 
         let mut freq_mod = SineOsc::new();
         freq_mod.set_frequency(8.0, inv_sample_rate);