compiled and working

dma_gpio/Cargo.lock

@@ -279,6 +279,7 @@ dependencies = [
  "micromath",
  "panic-halt",
  "panic-probe",
+ "static_cell",
  "tinybmp",
 ]
 
@@ -1033,6 +1034,15 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a2eb9349b6444b326872e140eb1cf5e7c522154d69e7a0ffb0fb81c06b37543f"
 
+[[package]]
+name = "static_cell"
+version = "2.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0530892bb4fa575ee0da4b86f86c667132a94b74bb72160f58ee5a4afec74c23"
+dependencies = [
+ "portable-atomic",
+]
+
 [[package]]
 name = "stm32-fmc"
 version = "0.3.2"

dma_gpio/Cargo.toml

@@ -26,3 +26,4 @@ tinybmp = "0.6.0"
 panic-probe = { version = "1.0.0", features = ["defmt"] }
 defmt-rtt = "1.1.0"
 defmt = "1.0.1"
+static_cell = "2.1.1"

dma_gpio/src/bin/main.rs

@@ -5,6 +5,7 @@
 use defmt::*;
 use embassy_executor::Spawner;
 use embassy_stm32::gpio::{Input, Output, Level, Pull, Speed};
+use embassy_sync::{blocking_mutex::raw::CriticalSectionRawMutex, pipe::Pipe};
 use embassy_time::{Duration, Timer};
 use dma_gpio::software_uart::{
     dma_timer::{init_tim6_for_uart, init_tim7_for_uart},
@@ -12,6 +13,7 @@ use dma_gpio::software_uart::{
     runtime::{rx_dma_task, tx_dma_task},
     debug::dump_tim6_regs,
 };
+use static_cell::StaticCell;
 use {defmt_rtt as _, panic_probe as _};
 
 /// SOFTWARE UART CONFIGURATION
@@ -25,36 +27,33 @@ const RX_RING_BYTES: usize = 4096;
 
 static PIPE_TX: Pipe<CriticalSectionRawMutex, PIPE_TX_SIZE> = Pipe::new();
 static PIPE_RX: Pipe<CriticalSectionRawMutex, PIPE_RX_SIZE> = Pipe::new();
-// Large hardware RX DMA circular buffer, scales with oversampling rate
+static RX_RING: StaticCell<[u8; RX_RING_BYTES]> = StaticCell::new();
-static mut RX_RING: [u8; RX_RING_BYTES] = [0; RX_RING_BYTES];
 
 #[embassy_executor::main]
 async fn main(spawner: Spawner) {
-    // Initialize peripheral access
+    let p = embassy_stm32::init(Default::default());
-    let mut p = embassy_stm32::init(Default::default());
+    info!("Hehe");
-    info!("UART DMA demo starting...");
 
-    // GPIO setup
+    let _rx = Input::new(p.PA3, Pull::Up);
-    let rx = Input::new(p.PA3, Pull::Up);
     let _tx = Output::new(p.PA2, Level::High, Speed::VeryHigh);
 
-    // Timer setup
     init_tim6_for_uart(p.TIM6, BAUD, TX_OVERSAMPLE);
     init_tim7_for_uart(p.TIM7, BAUD, RX_OVERSAMPLE);
-    dump_tim6_regs(); // debug
+    dump_tim6_regs();
 
-    // Spawn DMA tasks
+    // Safe one-time init from StaticCell
-    spawner.spawn(tx_dma_task(p.GPDMA1_CH0)).unwrap();
+    let ring: &mut [u8; RX_RING_BYTES] = RX_RING.init([0; RX_RING_BYTES]);
-    spawner.spawn(rx_dma_task(p.GPDMA1_CH1)).unwrap();
+
+    // Spawn tasks
+    spawner.spawn(tx_dma_task(p.GPDMA1_CH0, &PIPE_TX).unwrap());
+    spawner.spawn(rx_dma_task(p.GPDMA1_CH1, &PIPE_RX, ring).unwrap());
 
-    // UART config (8N1 default)
     let uart_cfg = UartConfig {
         data_bits: 8,
         parity: Parity::None,
         stop_bits: StopBits::One,
     };
 
-    // Main loop: send data periodically
     loop {
         write_uart_frames_to_pipe(&PIPE_TX, TX_PIN_BIT, b"Hello marshmallow\r\n", &uart_cfg).await;
         Timer::after(Duration::from_secs(2)).await;

dma_gpio/src/software_uart/runtime.rs

@@ -9,39 +9,47 @@ use embassy_stm32::{
 use embassy_sync::{blocking_mutex::raw::CriticalSectionRawMutex, pipe::Pipe};
 use embassy_time::Duration;
 use crate::software_uart::{
-    gpio_dma_uart_rx::TIM7_UP_REQ, gpio_dma_uart_tx::GpioDmaBsrrTx,
+    gpio_dma_uart_rx::TIM7_UP_REQ,
+    gpio_dma_uart_tx::GpioDmaBsrrTx,
     debug::{dump_dma_ch0_regs, dump_tim6_regs},
 };
 
 /// RX DMA task: reads GPIO samples paced by TIM7 and fills PIPE_RX
 #[task]
-pub async fn rx_dma_task(ch: Peri<'static, GPDMA1_CH1>) {
+pub async fn rx_dma_task(
-    let ring = unsafe { &mut RX_RING };
+    ch: Peri<'static, GPDMA1_CH1>,
+    pipe_rx: &'static Pipe<CriticalSectionRawMutex, 256>,
+    ring: &'static mut [u8],
+) {
     let gpioa_idr = embassy_stm32::pac::GPIOA.idr().as_ptr() as *mut u8;
 
     let mut opts = TransferOptions::default();
     opts.half_transfer_ir = true;
     opts.complete_transfer_ir = true;
 
+    // SAFETY: ring is exclusive to this task
     let mut rx = unsafe { DmaRingRx::new(ch, TIM7_UP_REQ, gpioa_idr, ring, opts) };
     rx.start();
 
     let mut chunk = [0u8; 256];
     loop {
         let _ = rx.read_exact(&mut chunk).await;
-        PIPE_RX.write(&chunk).await;
+        pipe_rx.write(&chunk).await;
     }
 }
 
 /// TX DMA task: dequeues prebuilt frames from PIPE_TX and writes to GPIOA.BSRR
 #[task]
-pub async fn tx_dma_task(ch: Peri<'static, GPDMA1_CH0>) {
+pub async fn tx_dma_task(
+    ch: Peri<'static, GPDMA1_CH0>,
+    pipe_tx: &'static Pipe<CriticalSectionRawMutex, 256>,
+) {
     let mut tx = GpioDmaBsrrTx::new(ch);
     info!("DMA TX task started");
 
     loop {
         let mut b = [0u8; 4];
-        let n = PIPE_TX.read(&mut b).await;
+        let n = pipe_tx.read(&mut b).await;
         if n != 4 {
             continue;
         }