fixing and working nonstop without timout

dma_gpio2/Cargo.toml

@@ -16,7 +16,7 @@ embassy-sync = { path = "/home/filip/programs/embassy/embassy-sync" }
 embassy-time = { path = "/home/filip/programs/embassy/embassy-time", features = ["tick-hz-32_768"] }
 embassy-hal-internal = { path = "/home/filip/programs/embassy/embassy-hal-internal" }
 embassy-usb = { path = "/home/filip/programs/embassy/embassy-usb" }
-embassy-stm32 = { path = "/home/filip/programs/embassy/embassy-stm32", features = ["unstable-pac", "stm32u575zi", "time-driver-tim2", "memory-x", "defmt"] }
+embassy-stm32 = { path = "/home/filip/programs/embassy/embassy-stm32", features = ["unstable-pac", "stm32u575zi", "time-driver-tim2", "memory-x", "defmt", "dma_debug"] }
 
 embedded-hal = "1.0.0"
 embedded-graphics = "0.8.1"

dma_gpio2/src/bin/main.rs

@@ -3,6 +3,7 @@
 #![no_main]
 
 use defmt::*;
+use embassy_stm32::dma::ringbuffer::Error;
 use embassy_executor::Spawner;
 use embassy_futures::yield_now;
 use embassy_stm32::dma::Request;
@@ -22,29 +23,6 @@ pub const TIM6_UP_REQ: Request = 4;
 
 static TX_RING: StaticCell<[u32; TX_RING_BYTES]> = StaticCell::new();
 
-use core::future::poll_fn;
-use core::task::Poll;
-
-// Wait until there is at least `needed` free space in the TX ring.
-async fn wait_for_space<'a>(
-    ring: &mut WritableRingBuffer<'a, u32>,
-    needed: usize,
-) {
-    poll_fn(|cx| {
-        let cap = ring.capacity();
-        let used = ring.len().unwrap_or(0);
-        let free = cap.saturating_sub(used);
-
-        if free >= needed {
-            Poll::Ready(())
-        } else {
-            ring.set_waker(cx.waker());
-            Poll::Pending
-        }
-    })
-    .await
-}
-
 #[embassy_executor::main]
 async fn main(_spawner: Spawner) {
     let p = embassy_stm32::init(Default::default());
@@ -59,7 +37,7 @@ async fn main(_spawner: Spawner) {
     let idle: u32 = 1u32 << TX_PIN_BIT;
 
     // Ring initialized to idle (line high).
-    let tx_ring_mem: &mut [u32; TX_RING_BYTES] = TX_RING.init([idle; TX_RING_BYTES]);
+    let tx_ring_mem: &mut [u32; TX_RING_BYTES] = TX_RING.init([0; TX_RING_BYTES]);
 
     let odr_ptr = embassy_stm32::pac::GPIOA.odr().as_ptr() as *mut u32;
 
@@ -77,6 +55,22 @@ async fn main(_spawner: Spawner) {
         )
     };
 
+    {
+        // Full idle buffer matching ring capacity.
+        let idle_buf = [idle; TX_RING_BYTES];
+
+        let written = tx_ring
+            .write_exact(&idle_buf)
+            .await
+            .expect("Failed to prefill TX ring with idle");
+
+        info!(
+            "TX ring prefilled with idle via write_exact: written={} cap={}",
+            written,
+            tx_ring.capacity()
+        );
+    }
+
     tx_ring.start();
     info!(
         "TX DMA ring started: cap_words={}",
@@ -120,17 +114,12 @@ async fn main(_spawner: Spawner) {
 
     loop {
         info!("tick start");
-        Timer::after(Duration::from_millis(400)).await;
+        //Timer::after(Duration::from_millis(400)).await;
-        info!("tick end");
+        //info!("tick end");
-
-        // Prepare scratch buffer with idle.
-        for w in frame_buf.iter_mut() {
-            *w = idle;
-        }
 
         let used = encode_uart_frames(
             TX_PIN_BIT,
-            b"Hello marshmallow\r\n",
+            b"Hihihi\r\n",
             &mut frame_buf,
         )
         .await;
@@ -149,17 +138,13 @@ async fn main(_spawner: Spawner) {
             &frame_buf[..preview]
         );
 
-        // Wait until the ring has room for this frame.
-        wait_for_space(&mut tx_ring, used).await;
-
         // Now it is safe to call write_exact.
-        match tx_ring.write_immediate(&frame_buf[..used]) {
+        match tx_ring.write_exact(&frame_buf[..used]).await {
-            Ok((written, remaining)) => {
+            Ok(written) => {
                 let len = tx_ring.len().unwrap_or(0);
                 info!(
-                    "write_immediate ok: written={} remaining={} ring_used={} ring_cap={}",
+                    "write_exact ok: written={} ring_used={} ring_cap={}",
                     written,
-                    remaining,
                     len,
                     tx_ring.capacity()
                 );
@@ -167,14 +152,23 @@ async fn main(_spawner: Spawner) {
             Err(e) => {
                 let len = tx_ring.len().unwrap_or(0);
                 warn!(
-                    "write_immediate error: {:?}, ring_used={} ring_cap={}",
+                    "write_exact error: {:?}, ring_used={} ring_cap={}",
                     e,
                     len,
                     tx_ring.capacity()
                 );
             }
-        }        
+            Err(Error::Overrun) => {
+                warn!("XYZ");
+                // DMA lapped you. Must resync:
+                tx_ring.request_reset(); // Stop DMA
+                tx_ring.clear();         // Clear buffer
+                tx_ring.start();         // Restart
+                                    // Retry writing frame
+            }
+        }
 
+        info!("tick end");
         yield_now().await;
     }
 }