compiled ping pong buffer setup

.gitignore

@@ -1,2 +1 @@
 *.pdf
-dma_example/

dma_gpio2/src/bin/main.rs

@@ -1,95 +1,71 @@
 // src/bin/main.rs
+
 #![no_std]
 #![no_main]
 
 use defmt::*;
 use embassy_executor::Spawner;
-use embassy_stm32::dma::Request;
+use embassy_futures::yield_now;
 use embassy_stm32::gpio::{Input, Output, Level, Pull, Speed};
-use embassy_time::{Duration, Timer};
+use embassy_stm32::dma::{TransferOptions, Transfer, Priority, Request};
-use embassy_stm32::dma::{TransferOptions, WritableRingBuffer};
 use dma_gpio::software_uart::{
     dma_timer::init_tim6_for_uart,
     gpio_dma_uart_tx::encode_uart_frames,
     debug::dump_tim6_regs,
 };
-use dma_gpio::config::{BAUD, TX_PIN_BIT, TX_OVERSAMPLE, TX_RING_BYTES};
+use dma_gpio::config::{BAUD, TX_PIN_BIT, TX_OVERSAMPLE};
 use static_cell::StaticCell;
-use core::slice;
 use {defmt_rtt as _, panic_probe as _};
 
+unsafe fn start_dma<'a>(
+    ch: embassy_hal_internal::Peri<'a, impl embassy_stm32::dma::Channel>,
+    request: Request,
+    odr_ptr: *mut u32,
+    buf: &'a [u32],
+    opts: TransferOptions,
+) -> Transfer<'a> {
+    // new_write itself is unsafe
+    unsafe { Transfer::new_write(ch, request, buf, odr_ptr, opts) }
+}
+
 pub const TIM6_UP_REQ: Request = 4;
-static TX_RING: StaticCell<[u32; TX_RING_BYTES]> = StaticCell::new();
+
+static BUF_A: StaticCell<[u32; 8]> = StaticCell::new();
+static BUF_B: StaticCell<[u32; 8]> = StaticCell::new();
 
 #[embassy_executor::main]
 async fn main(_spawner: Spawner) {
     let p = embassy_stm32::init(Default::default());
-    info!("DMA UART TX - Direct Buffer Modification");
+    let odr_ptr = embassy_stm32::pac::GPIOA.odr().as_ptr() as *mut u32;
-    
-    let _rx = Input::new(p.PA3, Pull::Up);
-    let _tx = Output::new(p.PA2, Level::High, Speed::VeryHigh);
 
     init_tim6_for_uart(p.TIM6, BAUD, TX_OVERSAMPLE);
     dump_tim6_regs();
 
-    // Initialize buffer - keep reference for modification
+    let buf_a = BUF_A.init([0u32; 8]);
-    let tx_ring_mem: &'static mut [u32; TX_RING_BYTES] = TX_RING.init([0; TX_RING_BYTES]);
+    let buf_b = BUF_B.init([0u32; 8]);
 
-    // Fill with UART idle state (pin high)
+    let mut opts = TransferOptions::default();
-    let pin_mask = 1u32 << TX_PIN_BIT;
+    opts.priority = Priority::VeryHigh;
-    for word in tx_ring_mem.iter_mut() {
+    opts.complete_transfer_ir = true;
-        *word = pin_mask;
-    }
 
-    // Create DMA ring buffer with a SEPARATE slice created from raw parts
+    let mut ch0 = p.GPDMA1_CH0;
-    // This allows us to keep modifying tx_ring_mem
+    let mut using_a = true;
-    let odr_ptr = embassy_stm32::pac::GPIOA.odr().as_ptr() as *mut u32;
-    let tx_opts = TransferOptions::default();
-    
-    let mut tx_ring = unsafe {
-        // Create a separate mutable slice pointing to the same memory
-        let dma_slice = slice::from_raw_parts_mut(
-            tx_ring_mem.as_mut_ptr(),
-            tx_ring_mem.len()
-        );
-        
-        WritableRingBuffer::new(
-            p.GPDMA1_CH0,
-            TIM6_UP_REQ,
-            odr_ptr,
-            dma_slice,
-            tx_opts,
-        )
-    };
-    
-    tx_ring.start();
-    info!("DMA started - continuously reading from buffer");
-    
-    // Temporary buffer for encoding
-    let mut frame_buf = [0u32; 4096];
 
     loop {
-        Timer::after(Duration::from_millis(400)).await;
+        let (dma_buf, cpu_buf) = if using_a {
+            (&*buf_a, &mut *buf_b)
+        } else {
+            (&*buf_b, &mut *buf_a)
+        };
 
-        // Encode the UART frames
+        let used = encode_uart_frames(TX_PIN_BIT, b"Hello marshmallow\r\n", cpu_buf).await;
-        let frame_len = encode_uart_frames(
-            TX_PIN_BIT,
-            b"Hello marshmallow\r\n",
-            &mut frame_buf
-        ).await;
 
-        info!("Encoded {} words, copying to buffer...", frame_len);
+        let transfer = unsafe {
+            start_dma(ch0.reborrow(), TIM6_UP_REQ, odr_ptr, &dma_buf[..used], opts)
+        };
+        transfer.await;
+        using_a = !using_a;
 
-        // Copy directly into the ring buffer memory
+        yield_now().await;
-        // DMA will automatically read and transmit this!
-        let copy_len = frame_len.min(TX_RING_BYTES);
-        tx_ring_mem[..copy_len].copy_from_slice(&frame_buf[..copy_len]);
-        
-        // Fill rest with idle state
-        for i in copy_len..TX_RING_BYTES {
-            tx_ring_mem[i] = pin_mask;
-        }
-        
-        info!("Buffer updated - DMA transmitting now");
     }
 }

dma_gpio2/src/config.rs

@@ -4,9 +4,9 @@ use crate::software_uart::uart_emulation::{Parity, StopBits, UartConfig};
 pub const BAUD: u32 = 9_600;
 pub const TX_PIN_BIT: u8 = 2; // PA2
 pub const TX_OVERSAMPLE: u16 = 1;
-pub const RX_OVERSAMPLE: u16 = 1;
+pub const RX_OVERSAMPLE: u16 = 16;
 pub const RX_RING_BYTES: usize = 4096;
-pub const TX_RING_BYTES: usize = 256;
+pub const TX_RING_BYTES: usize = 4096;
 pub const PIPE_RX_SIZE: usize = 256;
 
 pub const UART_CFG: UartConfig = UartConfig {