Synchronise sending and receiving I2S frames

hil-test/tests/i2s_async.rs

@@ -11,19 +11,29 @@
 #![no_main]
 
 use defmt_rtt as _;
+use embassy_sync::{blocking_mutex::raw::CriticalSectionRawMutex, signal::Signal};
 use esp_backtrace as _;
 use esp_hal::{
     clock::ClockControl,
     dma::{Dma, DmaChannel0, DmaPriority},
     gpio::Io,
     i2s::{asynch::*, DataFormat, I2s, I2sTx, Standard},
     peripheral::Peripheral,
-    peripherals::{I2S0, Peripherals},
+    peripherals::{Peripherals, I2S0},
     prelude::*,
     system::SystemControl,
     Async,
 };
 
+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;
 
 #[derive(Clone)]
@@ -53,13 +63,9 @@ impl Iterator for SampleSource {
 
 #[embassy_executor::task]
 async fn writer(
+    control: &'static Signal<CriticalSectionRawMutex, ()>,
     tx_buffer: &'static mut [u8],
-    i2s_tx: I2sTx<
-        'static,
-        I2S0,
-        DmaChannel0,
-        Async
-    >,
+    i2s_tx: I2sTx<'static, I2S0, DmaChannel0, Async>,
 ) {
     let mut samples = SampleSource::new();
     for b in tx_buffer.iter_mut() {
@@ -69,6 +75,7 @@ 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() {
@@ -144,8 +151,10 @@ 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());
+
         let mut rx_transfer = i2s_rx.read_dma_circular_async(rx_buffer).unwrap();
+        spawner.must_spawn(writer(send_next_frame, tx_buffer, i2s_tx));
 
         let mut rcv = [0u8; BUFFER_SIZE];
         let mut sample_idx = 0;
@@ -154,9 +163,14 @@ mod tests {
             let len = rx_transfer.pop(&mut rcv).await.unwrap();
             for &b in &rcv[..len] {
                 let expected = samples.next().unwrap();
-                assert_eq!(b, expected, "Sample #{} does not match ({} != {})", sample_idx, b, expected);
+                assert_eq!(
+                    b, expected,
+                    "Sample #{} does not match ({} != {})",
+                    sample_idx, b, expected
+                );
                 sample_idx += 1;
             }
+            send_next_frame.signal(());
         }
     }
 }