Merge pull request #1 from bogdan-petru/import/mcxa276-initial

feat(mcxa276): initial HAL import

1 files changed, 306 insertions, 0 deletions

diff --git a/src/uart.rs b/src/uart.rs
new file mode 100644
index 000000000..3209a318d
--- /dev/null
+++ b/src/uart.rs
@@ -0,0 +1,306 @@
+//! Minimal polling UART2 bring-up replicating MCUXpresso hello_world ordering.
+//! WARNING: This is a narrow implementation only for debug console (115200 8N1).
+
+use core::cell::RefCell;
+
+use cortex_m::interrupt::Mutex;
+use embassy_sync::signal::Signal;
+
+use crate::pac;
+
+// svd2rust defines the shared LPUART RegisterBlock under lpuart0; all instances reuse it.
+type Regs = pac::lpuart0::RegisterBlock;
+
+// Token-based instance pattern like embassy-imxrt
+pub trait Instance {
+    fn ptr() -> *const Regs;
+}
+
+/// Token for LPUART2 provided by embassy-hal-internal peripherals macro.
+pub type Lpuart2 = crate::peripherals::LPUART2;
+impl Instance for crate::peripherals::LPUART2 {
+    #[inline(always)]
+    fn ptr() -> *const Regs {
+        pac::Lpuart2::ptr()
+    }
+}
+
+// Also implement Instance for the Peri wrapper type
+impl Instance for embassy_hal_internal::Peri<'_, crate::peripherals::LPUART2> {
+    #[inline(always)]
+    fn ptr() -> *const Regs {
+        pac::Lpuart2::ptr()
+    }
+}
+
+/// UART configuration (explicit src_hz; no hardcoded frequencies)
+#[derive(Copy, Clone)]
+pub struct Config {
+    pub src_hz: u32,
+    pub baud: u32,
+    pub parity: Parity,
+    pub stop_bits: StopBits,
+}
+
+#[derive(Copy, Clone)]
+pub enum Parity {
+    None,
+    Even,
+    Odd,
+}
+#[derive(Copy, Clone)]
+pub enum StopBits {
+    One,
+    Two,
+}
+
+impl Config {
+    pub fn new(src_hz: u32) -> Self {
+        Self {
+            src_hz,
+            baud: 115_200,
+            parity: Parity::None,
+            stop_bits: StopBits::One,
+        }
+    }
+}
+
+/// Compute a valid (OSR, SBR) tuple for given source clock and baud.
+/// Uses a functional fold approach to find the best OSR/SBR combination
+/// with minimal baud rate error.
+fn compute_osr_sbr(src_hz: u32, baud: u32) -> (u8, u16) {
+    let (best_osr, best_sbr, _best_err) = (8u32..=32).fold(
+        (16u8, 4u16, u32::MAX), // (best_osr, best_sbr, best_err)
+        |(best_osr, best_sbr, best_err), osr| {
+            let denom = baud.saturating_mul(osr);
+            if denom == 0 {
+                return (best_osr, best_sbr, best_err);
+            }
+
+            let sbr = (src_hz + denom / 2) / denom; // round
+            if sbr == 0 || sbr > 0x1FFF {
+                return (best_osr, best_sbr, best_err);
+            }
+
+            let actual = src_hz / (osr * sbr);
+            let err = actual.abs_diff(baud);
+
+            // Update best if this is better, or same error but higher OSR
+            if err < best_err || (err == best_err && osr as u8 > best_osr) {
+                (osr as u8, sbr as u16, err)
+            } else {
+                (best_osr, best_sbr, best_err)
+            }
+        },
+    );
+    (best_osr, best_sbr)
+}
+
+/// Minimal UART handle for a specific instance I (store the zero-sized token like embassy)
+pub struct Uart<I: Instance> {
+    _inst: core::marker::PhantomData<I>,
+}
+
+impl<I: Instance> Uart<I> {
+    /// Create and initialize LPUART (reset + config). Clocks and pins must be prepared by the caller.
+    pub fn new(_inst: impl Instance, cfg: Config) -> Self {
+        let l = unsafe { &*I::ptr() };
+        // 1) software reset pulse
+        l.global().write(|w| w.rst().reset());
+        cortex_m::asm::delay(3); // Short delay for reset to take effect
+        l.global().write(|w| w.rst().no_effect());
+        cortex_m::asm::delay(10); // Allow peripheral to stabilize after reset
+                                  // 2) BAUD
+        let (osr, sbr) = compute_osr_sbr(cfg.src_hz, cfg.baud);
+        l.baud().modify(|_, w| {
+            let w = match cfg.stop_bits {
+                StopBits::One => w.sbns().one(),
+                StopBits::Two => w.sbns().two(),
+            };
+            // OSR field encodes (osr-1); use raw bits to avoid a long match on all variants
+            let raw_osr = osr.saturating_sub(1) as u8;
+            unsafe { w.osr().bits(raw_osr).sbr().bits(sbr) }
+        });
+        // 3) CTRL baseline and parity
+        l.ctrl().write(|w| {
+            let w = w.ilt().from_stop().idlecfg().idle_2();
+            let w = match cfg.parity {
+                Parity::None => w.pe().disabled(),
+                Parity::Even => w.pe().enabled().pt().even(),
+                Parity::Odd => w.pe().enabled().pt().odd(),
+            };
+            w.re().enabled().te().enabled().rie().disabled()
+        });
+        // 4) FIFOs and WATER: keep it simple for polling; disable FIFOs and set RX watermark to 0
+        l.fifo().modify(|_, w| {
+            w.txfe()
+                .disabled()
+                .rxfe()
+                .disabled()
+                .txflush()
+                .txfifo_rst()
+                .rxflush()
+                .rxfifo_rst()
+        });
+        l.water()
+            .modify(|_, w| unsafe { w.txwater().bits(0).rxwater().bits(0) });
+        Self {
+            _inst: core::marker::PhantomData,
+        }
+    }
+
+    /// Enable RX interrupts. The caller must ensure an appropriate IRQ handler is installed.
+    pub unsafe fn enable_rx_interrupts(&self) {
+        let l = &*I::ptr();
+        l.ctrl().modify(|_, w| w.rie().enabled());
+    }
+
+    #[inline(never)]
+    pub fn write_byte(&self, b: u8) {
+        let l = unsafe { &*I::ptr() };
+        // Timeout after ~10ms at 12MHz (assuming 115200 baud, should be plenty)
+        const DATA_OFFSET: usize = 0x1C; // DATA register offset inside LPUART block
+        let data_ptr = unsafe { (I::ptr() as *mut u8).add(DATA_OFFSET) };
+        for _ in 0..120000 {
+            if l.water().read().txcount().bits() == 0 {
+                unsafe { core::ptr::write_volatile(data_ptr, b) };
+                return;
+            }
+        }
+        // If timeout, skip the write to avoid hanging
+    }
+
+    #[inline(never)]
+    pub fn write_str_blocking(&self, s: &str) {
+        for &b in s.as_bytes() {
+            if b == b'\n' {
+                self.write_byte(b'\r');
+            }
+            self.write_byte(b);
+        }
+    }
+    pub fn read_byte_blocking(&self) -> u8 {
+        let l = unsafe { &*I::ptr() };
+        while !l.stat().read().rdrf().is_rxdata() {}
+        (l.data().read().bits() & 0xFF) as u8
+    }
+}
+
+// Simple ring buffer for UART RX data
+const RX_BUFFER_SIZE: usize = 256;
+pub struct RingBuffer {
+    buffer: [u8; RX_BUFFER_SIZE],
+    read_idx: usize,
+    write_idx: usize,
+    count: usize,
+}
+
+impl RingBuffer {
+    pub const fn new() -> Self {
+        Self {
+            buffer: [0; RX_BUFFER_SIZE],
+            read_idx: 0,
+            write_idx: 0,
+            count: 0,
+        }
+    }
+
+    pub fn push(&mut self, data: u8) -> bool {
+        if self.count >= RX_BUFFER_SIZE {
+            return false; // Buffer full
+        }
+        self.buffer[self.write_idx] = data;
+        self.write_idx = (self.write_idx + 1) % RX_BUFFER_SIZE;
+        self.count += 1;
+        true
+    }
+
+    pub fn pop(&mut self) -> Option<u8> {
+        if self.count == 0 {
+            return None;
+        }
+        let data = self.buffer[self.read_idx];
+        self.read_idx = (self.read_idx + 1) % RX_BUFFER_SIZE;
+        self.count -= 1;
+        Some(data)
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.count == 0
+    }
+
+    pub fn len(&self) -> usize {
+        self.count
+    }
+}
+
+// Global RX buffer shared between interrupt handler and UART instance
+static RX_BUFFER: Mutex<RefCell<RingBuffer>> = Mutex::new(RefCell::new(RingBuffer::new()));
+static RX_SIGNAL: Signal<embassy_sync::blocking_mutex::raw::CriticalSectionRawMutex, ()> = Signal::new();
+
+// Debug counter for interrupt handler calls
+static mut INTERRUPT_COUNT: u32 = 0;
+
+impl<I: Instance> Uart<I> {
+    /// Read a byte asynchronously using interrupts
+    pub async fn read_byte_async(&self) -> u8 {
+        loop {
+            // Check if we have data in the buffer
+            let byte = cortex_m::interrupt::free(|cs| {
+                let mut buffer = RX_BUFFER.borrow(cs).borrow_mut();
+                buffer.pop()
+            });
+
+            if let Some(byte) = byte {
+                return byte;
+            }
+
+            // Wait for the interrupt signal
+            RX_SIGNAL.wait().await;
+        }
+    }
+
+    /// Check if there's data available in the RX buffer
+    pub fn rx_data_available(&self) -> bool {
+        cortex_m::interrupt::free(|cs| {
+            let buffer = RX_BUFFER.borrow(cs).borrow();
+            !buffer.is_empty()
+        })
+    }
+
+    /// Try to read a byte from RX buffer (non-blocking)
+    pub fn try_read_byte(&self) -> Option<u8> {
+        cortex_m::interrupt::free(|cs| {
+            let mut buffer = RX_BUFFER.borrow(cs).borrow_mut();
+            buffer.pop()
+        })
+    }
+}
+
+/// Type-level handler for LPUART2 interrupts, compatible with bind_interrupts!.
+pub struct UartInterruptHandler;
+
+impl crate::interrupt::typelevel::Handler<crate::interrupt::typelevel::LPUART2> for UartInterruptHandler {
+    unsafe fn on_interrupt() {
+        INTERRUPT_COUNT += 1;
+
+        let lpuart = &*pac::Lpuart2::ptr();
+
+        // Check if we have RX data
+        if lpuart.stat().read().rdrf().is_rxdata() {
+            // Read the data byte
+            let data = (lpuart.data().read().bits() & 0xFF) as u8;
+
+            // Store in ring buffer
+            cortex_m::interrupt::free(|cs| {
+                let mut buffer = RX_BUFFER.borrow(cs).borrow_mut();
+                if buffer.push(data) {
+                    // Data added successfully, signal waiting tasks
+                    RX_SIGNAL.signal(());
+                }
+            });
+        }
+        // Always clear any error flags that might cause spurious interrupts
+        let _ = lpuart.stat().read();
+    }
+}