restored Rx ring properly well with the dma_gpio2 initialized

dma_gpio/src/bin/main.rs

@@ -4,24 +4,27 @@
 
 use defmt::*;
 use embassy_executor::Spawner;
+use embassy_stm32::dma::Request;
 use embassy_stm32::gpio::{Input, Output, Level, Pull, Speed};
 use embassy_sync::{blocking_mutex::raw::CriticalSectionRawMutex, pipe::Pipe};
-use embassy_time::{Duration, Timer};
 use embassy_stm32::dma::{TransferOptions, WritableRingBuffer};
 use dma_gpio::software_uart::{
     dma_timer::{init_tim6_for_uart, init_tim7_for_uart},
-    gpio_dma_uart_tx::{write_uart_frames_to_ring, TIM6_UP_REQ},
+    gpio_dma_uart_tx::encode_uart_frames,
     gpio_dma_uart_rx::rx_dma_task,
     debug::dump_tim6_regs,
 };
 use dma_gpio::config::{BAUD, TX_PIN_BIT, RX_OVERSAMPLE, TX_OVERSAMPLE};
 use dma_gpio::config::{TX_RING_BYTES, RX_RING_BYTES, PIPE_RX_SIZE};
 use static_cell::StaticCell;
+use embassy_futures::yield_now;
 use {defmt_rtt as _, panic_probe as _};
 
+pub const TIM6_UP_REQ: Request = 4;
+
 static PIPE_RX: Pipe<CriticalSectionRawMutex, PIPE_RX_SIZE> = Pipe::new();
-static RX_RING: StaticCell<[u8; RX_RING_BYTES]> = StaticCell::new();
 static TX_RING: StaticCell<[u32; TX_RING_BYTES]> = StaticCell::new();
+static RX_RING: StaticCell<[u8; RX_RING_BYTES]> = StaticCell::new();
 
 #[embassy_executor::main]
 async fn main(spawner: Spawner) {
@@ -64,16 +67,26 @@ async fn main(spawner: Spawner) {
     tx_ring.start();
     info!("TX DMA ring started");
 
+    let mut frame_buf = [0u32; 4096];
+
     loop {
         info!("tick start");
-        Timer::after(Duration::from_millis(100)).await;
+        // Timer::after(Duration::from_millis(100)).await;
-        info!("tick end");
+        // info!("tick end");
-        write_uart_frames_to_ring(
+        let used = encode_uart_frames(
-            &mut tx_ring,
             TX_PIN_BIT,
             b"Hello marshmallow\r\n",
-        ).await;
+            &mut frame_buf,
+        )
+        .await;
+
+        if used == 0 {
+            info!("encode_uart_frames() produced 0 words, skipping write");
+            yield_now().await;
+            continue;
+        }
+        let _ = tx_ring.write_exact(&frame_buf[..used]).await;
         info!("text");
-        Timer::after(Duration::from_secs(1)).await;
+        yield_now().await;
     }
 }

dma_gpio/src/software_uart/gpio_dma_uart_tx.rs

@@ -1,23 +1,28 @@
 // src/software_uart/gpio_dma_uart_tx.rs
-use embassy_stm32::dma::Request;
+use embassy_futures::yield_now;
-use embassy_stm32::dma::WritableRingBuffer;
 use crate::software_uart::uart_emulation::encode_uart_byte_cfg;
 use crate::config::UART_CFG;
 
-// kapitola 17.4.11 - 2 casovace pre 2 DMA
+pub async fn encode_uart_frames<'a>(
-pub const TIM6_UP_REQ: Request = 4; // Table 137: tim6_upd_dma, strana 687 STM32U5xx datasheet
-
-/// Push UART frames into the DMA-backed TX ring
-pub async fn write_uart_frames_to_ring(
-    ring: &mut WritableRingBuffer<'static, u32>,
     pin_bit: u8,
     bytes: &[u8],
-) {
+    out_buf: &'a mut [u32],
+) -> usize {
+    let mut offset = 0;
     for &b in bytes {
         let mut frame = [0u32; 12];
         let used = encode_uart_byte_cfg(pin_bit, b, &UART_CFG, &mut frame);
 
-        // Will wait until all words are written
+        if offset + used <= out_buf.len() {
-        ring.write_exact(&frame[..used]).await.unwrap();
+            out_buf[offset..offset + used].copy_from_slice(&frame[..used]);
+            offset += used;
+        } else {
+            break;
         }
+
+        // cooperative async yield
+        yield_now().await;
     }
+    offset
+}
+