Synchronise sending and receiving I2S frames

hil-test/tests/i2s_async.rs

@@ -23,6 +23,16 @@ use esp_hal::{
     system::SystemControl,
     Async,
 };
+use embassy_sync::{blocking_mutex::raw::CriticalSectionRawMutex, signal::Signal};
+
+macro_rules! mk_static {
+    ($t:ty,$val:expr) => {{
+        static STATIC_CELL: static_cell::StaticCell<$t> = static_cell::StaticCell::new();
+        #[deny(unused_attributes)]
+        let x = STATIC_CELL.uninit().write(($val));
+        x
+    }};
+}
 
 const BUFFER_SIZE: usize = 2000;
 
@@ -53,6 +63,7 @@ impl Iterator for SampleSource {
 
 #[embassy_executor::task]
 async fn writer(
+    control: &'static Signal<CriticalSectionRawMutex, ()>,
     tx_buffer: &'static mut [u8],
     i2s_tx: I2sTx<
         'static,
@@ -69,6 +80,7 @@ async fn writer(
     let mut tx_transfer = i2s_tx.write_dma_circular_async(tx_buffer).unwrap();
 
     loop {
+        control.wait().await;
         tx_transfer
             .push_with(|buffer| {
                 for b in buffer.iter_mut() {
@@ -144,13 +156,16 @@ mod tests {
             i2s.rx_conf().modify(|_, w| w.rx_update().set_bit());
         }
 
-        spawner.must_spawn(writer(tx_buffer, i2s_tx));
+        let send_next_frame = mk_static!(Signal<CriticalSectionRawMutex, ()>, Signal::new());
+
+        spawner.must_spawn(writer(send_next_frame, tx_buffer, i2s_tx));
         let mut rx_transfer = i2s_rx.read_dma_circular_async(rx_buffer).unwrap();
 
         let mut rcv = [0u8; BUFFER_SIZE];
         let mut sample_idx = 0;
         let mut samples = SampleSource::new();
         for _ in 0..30 {
+            send_next_frame.signal(());
             let len = rx_transfer.pop(&mut rcv).await.unwrap();
             for &b in &rcv[..len] {
                 let expected = samples.next().unwrap();