1 files changed, 165 insertions, 0 deletions

diff --git a/examples/mcxa/src/bin/raw_dma_scatter_gather.rs b/examples/mcxa/src/bin/raw_dma_scatter_gather.rs
new file mode 100644
index 000000000..eb9960764
--- /dev/null
+++ b/examples/mcxa/src/bin/raw_dma_scatter_gather.rs
@@ -0,0 +1,165 @@
+//! DMA scatter-gather transfer example for MCXA276.
+//!
+//! NOTE: this is a "raw dma" example! It exists as a proof of concept, as we don't have
+//! a high-level and safe API for. It should not be taken as typical, recommended, or
+//! stable usage!
+//!
+//! This example demonstrates using DMA with scatter/gather to chain multiple
+//! transfer descriptors. The first TCD transfers the first half of the buffer,
+//! then automatically loads the second TCD to transfer the second half.
+//!
+//! # Embassy-style features demonstrated:
+//! - `DmaChannel::new()` for channel creation
+//! - Scatter/gather with chained TCDs
+//! - Custom handler that delegates to HAL's `on_interrupt()` (best practice)
+
+#![no_std]
+#![no_main]
+
+use embassy_executor::Spawner;
+use embassy_mcxa::clocks::config::Div8;
+use embassy_mcxa::dma::{DmaChannel, Tcd};
+use static_cell::ConstStaticCell;
+use {defmt_rtt as _, embassy_mcxa as hal, panic_probe as _};
+
+// Source and destination buffers
+static SRC: ConstStaticCell<[u32; 12]> = ConstStaticCell::new([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]);
+static DST: ConstStaticCell<[u32; 12]> = ConstStaticCell::new([0; 12]);
+
+// TCD pool for scatter/gather - must be 32-byte aligned
+#[repr(C, align(32))]
+struct TcdPool([Tcd; 2]);
+
+static TCD_POOL: ConstStaticCell<TcdPool> = ConstStaticCell::new(TcdPool(
+    [Tcd {
+        saddr: 0,
+        soff: 0,
+        attr: 0,
+        nbytes: 0,
+        slast: 0,
+        daddr: 0,
+        doff: 0,
+        citer: 0,
+        dlast_sga: 0,
+        csr: 0,
+        biter: 0,
+    }; 2],
+));
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    // Small delay to allow probe-rs to attach after reset
+    for _ in 0..100_000 {
+        cortex_m::asm::nop();
+    }
+
+    let mut cfg = hal::config::Config::default();
+    cfg.clock_cfg.sirc.fro_12m_enabled = true;
+    cfg.clock_cfg.sirc.fro_lf_div = Some(Div8::no_div());
+    let p = hal::init(cfg);
+
+    defmt::info!("DMA scatter-gather transfer example starting...");
+
+    defmt::info!("EDMA scatter-gather transfer example begin.");
+
+    // Initialize buffers
+    let src = SRC.take();
+    let dst = DST.take();
+
+    defmt::info!("Source Buffer: {=[?]}", src.as_slice());
+    defmt::info!("Destination Buffer (before): {=[?]}", dst.as_slice());
+    defmt::info!("Configuring scatter-gather DMA with Embassy-style API...");
+
+    let dma_ch0 = DmaChannel::new(p.DMA_CH0);
+    let src_ptr = src.as_ptr();
+    let dst_ptr = dst.as_mut_ptr();
+
+    // Configure scatter-gather transfer using direct TCD access:
+    // This sets up TCD0 and TCD1 in RAM, and loads TCD0 into the channel.
+    // TCD0 transfers first half (SRC[0..4] -> DST[0..4]), then loads TCD1.
+    // TCD1 transfers second half (SRC[4..12] -> DST[4..12]), last TCD.
+    unsafe {
+        let tcds = &mut TCD_POOL.take().0;
+
+        // In the first transfer, copy
+        tcds[0] = Tcd {
+            saddr: src_ptr as u32,
+            soff: 4,
+            attr: 0x0202, // 32-bit src/dst
+            nbytes: 4 * 4,
+            slast: 0,
+            daddr: dst_ptr as u32,
+            doff: 4,
+            citer: 1,
+            dlast_sga: tcds.as_ptr().add(1) as i32,
+            // ESG (scatter/gather) for non-last, INTMAJOR for all
+            csr: 0x0012,
+            biter: 1,
+        };
+
+        tcds[1] = Tcd {
+            saddr: src_ptr.add(4) as u32,
+            soff: 4,
+            attr: 0x0202, // 32-bit src/dst
+            nbytes: 8 * 4,
+            slast: 0,
+            daddr: dst_ptr.add(4) as u32,
+            doff: 4,
+            citer: 1,
+            dlast_sga: 0,
+            // ESG (scatter/gather) for non-last, INTMAJOR for all
+            csr: 0x0002,
+            biter: 1,
+        };
+
+        // Load TCD0 into hardware registers
+        dma_ch0.load_tcd(&tcds[0]);
+    }
+
+    defmt::info!("Triggering first half transfer...");
+
+    let tcd = dma_ch0.tcd();
+
+    // Trigger first transfer (first half: SRC[0..4] -> DST[0..4])
+    // TCD0 is currently loaded.
+    unsafe {
+        dma_ch0.trigger_start();
+    }
+
+    // Wait for first half
+    loop {
+        if tcd.tcd_saddr().read().bits() != src_ptr as u32 {
+            defmt::info!("saddr: {=u32}", tcd.tcd_saddr().read().bits());
+            defmt::info!("srptr: {=u32}", src_ptr as u32);
+            break;
+        }
+    }
+
+    defmt::info!("First half transferred.");
+    defmt::info!("Triggering second half transfer...");
+
+    // Trigger second transfer (second half: SRC[4..8] -> DST[4..8])
+    // TCD1 should have been loaded by the scatter/gather engine.
+    unsafe {
+        dma_ch0.trigger_start();
+    }
+
+    // Wait for second half
+    while !dma_ch0.is_done() {
+        cortex_m::asm::nop();
+    }
+
+    defmt::info!("Second half transferred.");
+
+    defmt::info!("EDMA scatter-gather transfer example finish.");
+    defmt::info!("Destination Buffer (after): {=[?]}", dst.as_slice());
+
+    // Verify: DST should match SRC
+    let mismatch = src != dst;
+
+    if mismatch {
+        defmt::error!("FAIL: Mismatch detected!");
+    } else {
+        defmt::info!("PASS: Data verified.");
+    }
+}