feat: add display UI with splash screen, dashboard, and RSSI sparkline

Implement full SSD1306 OLED display support:
- Splash screen on boot (1.5s) with project name, version, board
- Dashboard showing radio state, config, counters, RSSI/SNR
- RSSI history sparkline (64-sample ring buffer, 2px-wide bars)
- DisplayOn/DisplayOff host commands routed via dedicated channel
- Pure render functions against generic DrawTarget (no hardware coupling)
- Display on/off control bypasses radio task entirely

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/embassy-executor/src/arch/avr.rs

@@ -0,0 +1,72 @@
+#[cfg(feature = "executor-interrupt")]
+compile_error!("`executor-interrupt` is not supported with `arch-avr`.");
+
+#[cfg(feature = "executor-thread")]
+pub use thread::*;
+#[cfg(feature = "executor-thread")]
+mod thread {
+    use core::marker::PhantomData;
+
+    pub use embassy_executor_macros::main_avr as main;
+    use portable_atomic::{AtomicBool, Ordering};
+
+    use crate::{raw, Spawner};
+
+    static SIGNAL_WORK_THREAD_MODE: AtomicBool = AtomicBool::new(false);
+
+    #[export_name = "__pender"]
+    fn __pender(_context: *mut ()) {
+        SIGNAL_WORK_THREAD_MODE.store(true, Ordering::SeqCst);
+    }
+
+    /// avr Executor
+    pub struct Executor {
+        inner: raw::Executor,
+        not_send: PhantomData<*mut ()>,
+    }
+
+    impl Executor {
+        /// Create a new Executor.
+        pub fn new() -> Self {
+            Self {
+                inner: raw::Executor::new(core::ptr::null_mut()),
+                not_send: PhantomData,
+            }
+        }
+
+        /// Run the executor.
+        ///
+        /// The `init` closure is called with a [`Spawner`] that spawns tasks on
+        /// this executor. Use it to spawn the initial task(s). After `init` returns,
+        /// the executor starts running the tasks.
+        ///
+        /// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
+        /// for example by passing it as an argument to the initial tasks.
+        ///
+        /// This function requires `&'static mut self`. This means you have to store the
+        /// Executor instance in a place where it'll live forever and grants you mutable
+        /// access. There's a few ways to do this:
+        ///
+        /// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
+        /// - a `static mut` (unsafe)
+        /// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
+        ///
+        /// This function never returns.
+        pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
+            init(self.inner.spawner());
+
+            loop {
+                unsafe {
+                    avr_device::interrupt::disable();
+                    if !SIGNAL_WORK_THREAD_MODE.swap(false, Ordering::SeqCst) {
+                        avr_device::interrupt::enable();
+                        avr_device::asm::sleep();
+                    } else {
+                        avr_device::interrupt::enable();
+                        self.inner.poll();
+                    }
+                }
+            }
+        }
+    }
+}

vendor/embassy-executor/src/arch/cortex_m.rs

@@ -0,0 +1,231 @@
+#[export_name = "__pender"]
+#[cfg(any(feature = "executor-thread", feature = "executor-interrupt"))]
+fn __pender(context: *mut ()) {
+    unsafe {
+        // Safety: `context` is either `usize::MAX` created by `Executor::run`, or a valid interrupt
+        // request number given to `InterruptExecutor::start`.
+
+        let context = context as usize;
+
+        #[cfg(feature = "executor-thread")]
+        // Try to make Rust optimize the branching away if we only use thread mode.
+        if !cfg!(feature = "executor-interrupt") || context == THREAD_PENDER {
+            core::arch::asm!("sev");
+            return;
+        }
+
+        #[cfg(feature = "executor-interrupt")]
+        {
+            use cortex_m::interrupt::InterruptNumber;
+            use cortex_m::peripheral::NVIC;
+
+            #[derive(Clone, Copy)]
+            struct Irq(u16);
+            unsafe impl InterruptNumber for Irq {
+                fn number(self) -> u16 {
+                    self.0
+                }
+            }
+
+            let irq = Irq(context as u16);
+
+            // STIR is faster, but is only available in v7 and higher.
+            #[cfg(not(armv6m))]
+            {
+                let mut nvic: NVIC = core::mem::transmute(());
+                nvic.request(irq);
+            }
+
+            #[cfg(armv6m)]
+            NVIC::pend(irq);
+        }
+    }
+}
+
+#[cfg(feature = "executor-thread")]
+pub use thread::*;
+#[cfg(feature = "executor-thread")]
+mod thread {
+    pub(super) const THREAD_PENDER: usize = usize::MAX;
+
+    use core::arch::asm;
+    use core::marker::PhantomData;
+
+    pub use embassy_executor_macros::main_cortex_m as main;
+
+    use crate::{raw, Spawner};
+
+    /// Thread mode executor, using WFE/SEV.
+    ///
+    /// This is the simplest and most common kind of executor. It runs on
+    /// thread mode (at the lowest priority level), and uses the `WFE` ARM instruction
+    /// to sleep when it has no more work to do. When a task is woken, a `SEV` instruction
+    /// is executed, to make the `WFE` exit from sleep and poll the task.
+    ///
+    /// This executor allows for ultra low power consumption for chips where `WFE`
+    /// triggers low-power sleep without extra steps. If your chip requires extra steps,
+    /// you may use [`raw::Executor`] directly to program custom behavior.
+    pub struct Executor {
+        inner: raw::Executor,
+        not_send: PhantomData<*mut ()>,
+    }
+
+    impl Executor {
+        /// Create a new Executor.
+        pub fn new() -> Self {
+            Self {
+                inner: raw::Executor::new(THREAD_PENDER as *mut ()),
+                not_send: PhantomData,
+            }
+        }
+
+        /// Run the executor.
+        ///
+        /// The `init` closure is called with a [`Spawner`] that spawns tasks on
+        /// this executor. Use it to spawn the initial task(s). After `init` returns,
+        /// the executor starts running the tasks.
+        ///
+        /// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
+        /// for example by passing it as an argument to the initial tasks.
+        ///
+        /// This function requires `&'static mut self`. This means you have to store the
+        /// Executor instance in a place where it'll live forever and grants you mutable
+        /// access. There's a few ways to do this:
+        ///
+        /// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
+        /// - a `static mut` (unsafe)
+        /// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
+        ///
+        /// This function never returns.
+        pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
+            init(self.inner.spawner());
+
+            loop {
+                unsafe {
+                    self.inner.poll();
+                    asm!("wfe");
+                };
+            }
+        }
+    }
+}
+
+#[cfg(feature = "executor-interrupt")]
+pub use interrupt::*;
+#[cfg(feature = "executor-interrupt")]
+mod interrupt {
+    use core::cell::{Cell, UnsafeCell};
+    use core::mem::MaybeUninit;
+
+    use cortex_m::interrupt::InterruptNumber;
+    use cortex_m::peripheral::NVIC;
+    use critical_section::Mutex;
+
+    use crate::raw;
+
+    /// Interrupt mode executor.
+    ///
+    /// This executor runs tasks in interrupt mode. The interrupt handler is set up
+    /// to poll tasks, and when a task is woken the interrupt is pended from software.
+    ///
+    /// This allows running async tasks at a priority higher than thread mode. One
+    /// use case is to leave thread mode free for non-async tasks. Another use case is
+    /// to run multiple executors: one in thread mode for low priority tasks and another in
+    /// interrupt mode for higher priority tasks. Higher priority tasks will preempt lower
+    /// priority ones.
+    ///
+    /// It is even possible to run multiple interrupt mode executors at different priorities,
+    /// by assigning different priorities to the interrupts. For an example on how to do this,
+    /// See the 'multiprio' example for 'embassy-nrf'.
+    ///
+    /// To use it, you have to pick an interrupt that won't be used by the hardware.
+    /// Some chips reserve some interrupts for this purpose, sometimes named "software interrupts" (SWI).
+    /// If this is not the case, you may use an interrupt from any unused peripheral.
+    ///
+    /// It is somewhat more complex to use, it's recommended to use the thread-mode
+    /// [`Executor`] instead, if it works for your use case.
+    pub struct InterruptExecutor {
+        started: Mutex<Cell<bool>>,
+        executor: UnsafeCell<MaybeUninit<raw::Executor>>,
+    }
+
+    unsafe impl Send for InterruptExecutor {}
+    unsafe impl Sync for InterruptExecutor {}
+
+    impl InterruptExecutor {
+        /// Create a new, not started `InterruptExecutor`.
+        #[inline]
+        pub const fn new() -> Self {
+            Self {
+                started: Mutex::new(Cell::new(false)),
+                executor: UnsafeCell::new(MaybeUninit::uninit()),
+            }
+        }
+
+        /// Executor interrupt callback.
+        ///
+        /// # Safety
+        ///
+        /// - You MUST call this from the interrupt handler, and from nowhere else.
+        /// - You must not call this before calling `start()`.
+        pub unsafe fn on_interrupt(&'static self) {
+            let executor = unsafe { (&*self.executor.get()).assume_init_ref() };
+            executor.poll();
+        }
+
+        /// Start the executor.
+        ///
+        /// This initializes the executor, enables the interrupt, and returns.
+        /// The executor keeps running in the background through the interrupt.
+        ///
+        /// This returns a [`SendSpawner`] you can use to spawn tasks on it. A [`SendSpawner`]
+        /// is returned instead of a [`Spawner`](embassy_executor::Spawner) because the executor effectively runs in a
+        /// different "thread" (the interrupt), so spawning tasks on it is effectively
+        /// sending them.
+        ///
+        /// To obtain a [`Spawner`](embassy_executor::Spawner) for this executor, use [`Spawner::for_current_executor()`](embassy_executor::Spawner::for_current_executor()) from
+        /// a task running in it.
+        ///
+        /// # Interrupt requirements
+        ///
+        /// You must write the interrupt handler yourself, and make it call [`on_interrupt()`](Self::on_interrupt).
+        ///
+        /// This method already enables (unmasks) the interrupt, you must NOT do it yourself.
+        ///
+        /// You must set the interrupt priority before calling this method. You MUST NOT
+        /// do it after.
+        ///
+        pub fn start(&'static self, irq: impl InterruptNumber) -> crate::SendSpawner {
+            if critical_section::with(|cs| self.started.borrow(cs).replace(true)) {
+                panic!("InterruptExecutor::start() called multiple times on the same executor.");
+            }
+
+            unsafe {
+                (&mut *self.executor.get())
+                    .as_mut_ptr()
+                    .write(raw::Executor::new(irq.number() as *mut ()))
+            }
+
+            let executor = unsafe { (&*self.executor.get()).assume_init_ref() };
+
+            unsafe { NVIC::unmask(irq) }
+
+            executor.spawner().make_send()
+        }
+
+        /// Get a SendSpawner for this executor
+        ///
+        /// This returns a [`SendSpawner`] you can use to spawn tasks on this
+        /// executor.
+        ///
+        /// This MUST only be called on an executor that has already been started.
+        /// The function will panic otherwise.
+        pub fn spawner(&'static self) -> crate::SendSpawner {
+            if !critical_section::with(|cs| self.started.borrow(cs).get()) {
+                panic!("InterruptExecutor::spawner() called on uninitialized executor.");
+            }
+            let executor = unsafe { (&*self.executor.get()).assume_init_ref() };
+            executor.spawner().make_send()
+        }
+    }
+}

vendor/embassy-executor/src/arch/riscv32.rs

@@ -0,0 +1,80 @@
+#[cfg(feature = "executor-interrupt")]
+compile_error!("`executor-interrupt` is not supported with `arch-riscv32`.");
+
+#[cfg(feature = "executor-thread")]
+pub use thread::*;
+#[cfg(feature = "executor-thread")]
+mod thread {
+    use core::marker::PhantomData;
+    use core::sync::atomic::{AtomicBool, Ordering};
+
+    pub use embassy_executor_macros::main_riscv as main;
+
+    use crate::{raw, Spawner};
+
+    /// global atomic used to keep track of whether there is work to do since sev() is not available on RISCV
+    static SIGNAL_WORK_THREAD_MODE: AtomicBool = AtomicBool::new(false);
+
+    #[export_name = "__pender"]
+    fn __pender(_context: *mut ()) {
+        SIGNAL_WORK_THREAD_MODE.store(true, Ordering::SeqCst);
+    }
+
+    /// RISCV32 Executor
+    pub struct Executor {
+        inner: raw::Executor,
+        not_send: PhantomData<*mut ()>,
+    }
+
+    impl Executor {
+        /// Create a new Executor.
+        pub fn new() -> Self {
+            Self {
+                inner: raw::Executor::new(core::ptr::null_mut()),
+                not_send: PhantomData,
+            }
+        }
+
+        /// Run the executor.
+        ///
+        /// The `init` closure is called with a [`Spawner`] that spawns tasks on
+        /// this executor. Use it to spawn the initial task(s). After `init` returns,
+        /// the executor starts running the tasks.
+        ///
+        /// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
+        /// for example by passing it as an argument to the initial tasks.
+        ///
+        /// This function requires `&'static mut self`. This means you have to store the
+        /// Executor instance in a place where it'll live forever and grants you mutable
+        /// access. There's a few ways to do this:
+        ///
+        /// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
+        /// - a `static mut` (unsafe)
+        /// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
+        ///
+        /// This function never returns.
+        pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
+            init(self.inner.spawner());
+
+            loop {
+                unsafe {
+                    self.inner.poll();
+                    // we do not care about race conditions between the load and store operations, interrupts
+                    //will only set this value to true.
+                    critical_section::with(|_| {
+                        // if there is work to do, loop back to polling
+                        // TODO can we relax this?
+                        if SIGNAL_WORK_THREAD_MODE.load(Ordering::SeqCst) {
+                            SIGNAL_WORK_THREAD_MODE.store(false, Ordering::SeqCst);
+                        }
+                        // if not, wait for interrupt
+                        else {
+                            core::arch::asm!("wfi");
+                        }
+                    });
+                    // if an interrupt occurred while waiting, it will be serviced here
+                }
+            }
+        }
+    }
+}

vendor/embassy-executor/src/arch/spin.rs

@@ -0,0 +1,58 @@
+#[cfg(feature = "executor-interrupt")]
+compile_error!("`executor-interrupt` is not supported with `arch-spin`.");
+
+#[cfg(feature = "executor-thread")]
+pub use thread::*;
+#[cfg(feature = "executor-thread")]
+mod thread {
+    use core::marker::PhantomData;
+
+    pub use embassy_executor_macros::main_spin as main;
+
+    use crate::{raw, Spawner};
+
+    #[export_name = "__pender"]
+    fn __pender(_context: *mut ()) {}
+
+    /// Spin Executor
+    pub struct Executor {
+        inner: raw::Executor,
+        not_send: PhantomData<*mut ()>,
+    }
+
+    impl Executor {
+        /// Create a new Executor.
+        pub fn new() -> Self {
+            Self {
+                inner: raw::Executor::new(core::ptr::null_mut()),
+                not_send: PhantomData,
+            }
+        }
+
+        /// Run the executor.
+        ///
+        /// The `init` closure is called with a [`Spawner`] that spawns tasks on
+        /// this executor. Use it to spawn the initial task(s). After `init` returns,
+        /// the executor starts running the tasks.
+        ///
+        /// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
+        /// for example by passing it as an argument to the initial tasks.
+        ///
+        /// This function requires `&'static mut self`. This means you have to store the
+        /// Executor instance in a place where it'll live forever and grants you mutable
+        /// access. There's a few ways to do this:
+        ///
+        /// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
+        /// - a `static mut` (unsafe)
+        /// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
+        ///
+        /// This function never returns.
+        pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
+            init(self.inner.spawner());
+
+            loop {
+                unsafe { self.inner.poll() };
+            }
+        }
+    }
+}

vendor/embassy-executor/src/arch/std.rs

@@ -0,0 +1,94 @@
+#[cfg(feature = "executor-interrupt")]
+compile_error!("`executor-interrupt` is not supported with `arch-std`.");
+
+#[cfg(feature = "executor-thread")]
+pub use thread::*;
+#[cfg(feature = "executor-thread")]
+mod thread {
+    use std::marker::PhantomData;
+    use std::sync::{Condvar, Mutex};
+
+    pub use embassy_executor_macros::main_std as main;
+
+    use crate::{raw, Spawner};
+
+    #[export_name = "__pender"]
+    fn __pender(context: *mut ()) {
+        let signaler: &'static Signaler = unsafe { std::mem::transmute(context) };
+        signaler.signal()
+    }
+
+    /// Single-threaded std-based executor.
+    pub struct Executor {
+        inner: raw::Executor,
+        not_send: PhantomData<*mut ()>,
+        signaler: &'static Signaler,
+    }
+
+    impl Executor {
+        /// Create a new Executor.
+        pub fn new() -> Self {
+            let signaler = Box::leak(Box::new(Signaler::new()));
+            Self {
+                inner: raw::Executor::new(signaler as *mut Signaler as *mut ()),
+                not_send: PhantomData,
+                signaler,
+            }
+        }
+
+        /// Run the executor.
+        ///
+        /// The `init` closure is called with a [`Spawner`] that spawns tasks on
+        /// this executor. Use it to spawn the initial task(s). After `init` returns,
+        /// the executor starts running the tasks.
+        ///
+        /// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
+        /// for example by passing it as an argument to the initial tasks.
+        ///
+        /// This function requires `&'static mut self`. This means you have to store the
+        /// Executor instance in a place where it'll live forever and grants you mutable
+        /// access. There's a few ways to do this:
+        ///
+        /// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
+        /// - a `static mut` (unsafe)
+        /// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
+        ///
+        /// This function never returns.
+        pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
+            init(self.inner.spawner());
+
+            loop {
+                unsafe { self.inner.poll() };
+                self.signaler.wait()
+            }
+        }
+    }
+
+    struct Signaler {
+        mutex: Mutex<bool>,
+        condvar: Condvar,
+    }
+
+    impl Signaler {
+        fn new() -> Self {
+            Self {
+                mutex: Mutex::new(false),
+                condvar: Condvar::new(),
+            }
+        }
+
+        fn wait(&self) {
+            let mut signaled = self.mutex.lock().unwrap();
+            while !*signaled {
+                signaled = self.condvar.wait(signaled).unwrap();
+            }
+            *signaled = false;
+        }
+
+        fn signal(&self) {
+            let mut signaled = self.mutex.lock().unwrap();
+            *signaled = true;
+            self.condvar.notify_one();
+        }
+    }
+}

vendor/embassy-executor/src/arch/wasm.rs

@@ -0,0 +1,83 @@
+#[cfg(feature = "executor-interrupt")]
+compile_error!("`executor-interrupt` is not supported with `arch-wasm`.");
+
+#[cfg(feature = "executor-thread")]
+pub use thread::*;
+#[cfg(feature = "executor-thread")]
+mod thread {
+
+    use core::marker::PhantomData;
+
+    pub use embassy_executor_macros::main_wasm as main;
+    use js_sys::Promise;
+    use wasm_bindgen::prelude::*;
+
+    use crate::raw::util::UninitCell;
+    use crate::{raw, Spawner};
+
+    #[export_name = "__pender"]
+    fn __pender(context: *mut ()) {
+        let signaler: &'static WasmContext = unsafe { std::mem::transmute(context) };
+        let _ = signaler.promise.then(unsafe { signaler.closure.as_mut() });
+    }
+
+    pub(crate) struct WasmContext {
+        promise: Promise,
+        closure: UninitCell<Closure<dyn FnMut(JsValue)>>,
+    }
+
+    impl WasmContext {
+        pub fn new() -> Self {
+            Self {
+                promise: Promise::resolve(&JsValue::undefined()),
+                closure: UninitCell::uninit(),
+            }
+        }
+    }
+
+    /// WASM executor, wasm_bindgen to schedule tasks on the JS event loop.
+    pub struct Executor {
+        inner: raw::Executor,
+        ctx: &'static WasmContext,
+        not_send: PhantomData<*mut ()>,
+    }
+
+    impl Executor {
+        /// Create a new Executor.
+        pub fn new() -> Self {
+            let ctx = Box::leak(Box::new(WasmContext::new()));
+            Self {
+                inner: raw::Executor::new(ctx as *mut WasmContext as *mut ()),
+                ctx,
+                not_send: PhantomData,
+            }
+        }
+
+        /// Run the executor.
+        ///
+        /// The `init` closure is called with a [`Spawner`] that spawns tasks on
+        /// this executor. Use it to spawn the initial task(s). After `init` returns,
+        /// the executor starts running the tasks.
+        ///
+        /// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
+        /// for example by passing it as an argument to the initial tasks.
+        ///
+        /// This function requires `&'static mut self`. This means you have to store the
+        /// Executor instance in a place where it'll live forever and grants you mutable
+        /// access. There's a few ways to do this:
+        ///
+        /// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
+        /// - a `static mut` (unsafe)
+        /// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
+        pub fn start(&'static mut self, init: impl FnOnce(Spawner)) {
+            unsafe {
+                let executor = &self.inner;
+                let future = Closure::new(move |_| {
+                    executor.poll();
+                });
+                self.ctx.closure.write_in_place(|| future);
+                init(self.inner.spawner());
+            }
+        }
+    }
+}

vendor/embassy-executor/src/fmt.rs

@@ -0,0 +1,270 @@
+#![macro_use]
+#![allow(unused)]
+
+use core::fmt::{Debug, Display, LowerHex};
+
+#[cfg(all(feature = "defmt", feature = "log"))]
+compile_error!("You may not enable both `defmt` and `log` features.");
+
+#[collapse_debuginfo(yes)]
+macro_rules! assert {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert!($($x)*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! assert_eq {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert_eq!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert_eq!($($x)*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! assert_ne {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert_ne!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert_ne!($($x)*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! debug_assert {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert!($($x)*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! debug_assert_eq {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert_eq!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert_eq!($($x)*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! debug_assert_ne {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert_ne!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert_ne!($($x)*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! todo {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::todo!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::todo!($($x)*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! unreachable {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::unreachable!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::unreachable!($($x)*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! panic {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::panic!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::panic!($($x)*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! trace {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::trace!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::trace!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! debug {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::debug!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! info {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::info!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::info!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! warn {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::warn!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::warn!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+#[collapse_debuginfo(yes)]
+macro_rules! error {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::error!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::error!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+#[cfg(feature = "defmt")]
+#[collapse_debuginfo(yes)]
+macro_rules! unwrap {
+    ($($x:tt)*) => {
+        ::defmt::unwrap!($($x)*)
+    };
+}
+
+#[cfg(not(feature = "defmt"))]
+#[collapse_debuginfo(yes)]
+macro_rules! unwrap {
+    ($arg:expr) => {
+        match $crate::fmt::Try::into_result($arg) {
+            ::core::result::Result::Ok(t) => t,
+            ::core::result::Result::Err(e) => {
+                ::core::panic!("unwrap of `{}` failed: {:?}", ::core::stringify!($arg), e);
+            }
+        }
+    };
+    ($arg:expr, $($msg:expr),+ $(,)? ) => {
+        match $crate::fmt::Try::into_result($arg) {
+            ::core::result::Result::Ok(t) => t,
+            ::core::result::Result::Err(e) => {
+                ::core::panic!("unwrap of `{}` failed: {}: {:?}", ::core::stringify!($arg), ::core::format_args!($($msg,)*), e);
+            }
+        }
+    }
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub struct NoneError;
+
+pub trait Try {
+    type Ok;
+    type Error;
+    fn into_result(self) -> Result<Self::Ok, Self::Error>;
+}
+
+impl<T> Try for Option<T> {
+    type Ok = T;
+    type Error = NoneError;
+
+    #[inline]
+    fn into_result(self) -> Result<T, NoneError> {
+        self.ok_or(NoneError)
+    }
+}
+
+impl<T, E> Try for Result<T, E> {
+    type Ok = T;
+    type Error = E;
+
+    #[inline]
+    fn into_result(self) -> Self {
+        self
+    }
+}
+
+pub(crate) struct Bytes<'a>(pub &'a [u8]);
+
+impl<'a> Debug for Bytes<'a> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        write!(f, "{:#02x?}", self.0)
+    }
+}
+
+impl<'a> Display for Bytes<'a> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        write!(f, "{:#02x?}", self.0)
+    }
+}
+
+impl<'a> LowerHex for Bytes<'a> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        write!(f, "{:#02x?}", self.0)
+    }
+}
+
+#[cfg(feature = "defmt")]
+impl<'a> defmt::Format for Bytes<'a> {
+    fn format(&self, fmt: defmt::Formatter) {
+        defmt::write!(fmt, "{:02x}", self.0)
+    }
+}

vendor/embassy-executor/src/lib.rs

@@ -0,0 +1,150 @@
+#![cfg_attr(not(any(feature = "arch-std", feature = "arch-wasm")), no_std)]
+#![allow(clippy::new_without_default)]
+#![doc = include_str!("../README.md")]
+#![warn(missing_docs)]
+
+//! ## Feature flags
+#![doc = document_features::document_features!(feature_label = r#"<span class="stab portability"><code>{feature}</code></span>"#)]
+
+// This mod MUST go first, so that the others see its macros.
+pub(crate) mod fmt;
+
+pub use embassy_executor_macros::task;
+
+macro_rules! check_at_most_one {
+    (@amo [$($feats:literal)*] [] [$($res:tt)*]) => {
+        #[cfg(any($($res)*))]
+        compile_error!(concat!("At most one of these features can be enabled at the same time:", $(" `", $feats, "`",)*));
+    };
+    (@amo $feats:tt [$curr:literal $($rest:literal)*] [$($res:tt)*]) => {
+        check_at_most_one!(@amo $feats [$($rest)*] [$($res)* $(all(feature=$curr, feature=$rest),)*]);
+    };
+    ($($f:literal),*$(,)?) => {
+        check_at_most_one!(@amo [$($f)*] [$($f)*] []);
+    };
+}
+check_at_most_one!(
+    "arch-avr",
+    "arch-cortex-m",
+    "arch-riscv32",
+    "arch-std",
+    "arch-wasm",
+    "arch-spin",
+);
+
+#[cfg(feature = "_arch")]
+#[cfg_attr(feature = "arch-avr", path = "arch/avr.rs")]
+#[cfg_attr(feature = "arch-cortex-m", path = "arch/cortex_m.rs")]
+#[cfg_attr(feature = "arch-riscv32", path = "arch/riscv32.rs")]
+#[cfg_attr(feature = "arch-std", path = "arch/std.rs")]
+#[cfg_attr(feature = "arch-wasm", path = "arch/wasm.rs")]
+#[cfg_attr(feature = "arch-spin", path = "arch/spin.rs")]
+mod arch;
+
+#[cfg(feature = "_arch")]
+#[allow(unused_imports)] // don't warn if the module is empty.
+pub use arch::*;
+
+pub mod raw;
+
+mod spawner;
+pub use spawner::*;
+
+mod config {
+    #![allow(unused)]
+    include!(concat!(env!("OUT_DIR"), "/config.rs"));
+}
+
+/// Implementation details for embassy macros.
+/// Do not use. Used for macros and HALs only. Not covered by semver guarantees.
+#[doc(hidden)]
+#[cfg(not(feature = "nightly"))]
+pub mod _export {
+    use core::alloc::Layout;
+    use core::cell::{Cell, UnsafeCell};
+    use core::future::Future;
+    use core::mem::MaybeUninit;
+    use core::ptr::null_mut;
+
+    use critical_section::{CriticalSection, Mutex};
+
+    use crate::raw::TaskPool;
+
+    struct Arena<const N: usize> {
+        buf: UnsafeCell<MaybeUninit<[u8; N]>>,
+        ptr: Mutex<Cell<*mut u8>>,
+    }
+
+    unsafe impl<const N: usize> Sync for Arena<N> {}
+    unsafe impl<const N: usize> Send for Arena<N> {}
+
+    impl<const N: usize> Arena<N> {
+        const fn new() -> Self {
+            Self {
+                buf: UnsafeCell::new(MaybeUninit::uninit()),
+                ptr: Mutex::new(Cell::new(null_mut())),
+            }
+        }
+
+        fn alloc<T>(&'static self, cs: CriticalSection) -> &'static mut MaybeUninit<T> {
+            let layout = Layout::new::<T>();
+
+            let start = self.buf.get().cast::<u8>();
+            let end = unsafe { start.add(N) };
+
+            let mut ptr = self.ptr.borrow(cs).get();
+            if ptr.is_null() {
+                ptr = self.buf.get().cast::<u8>();
+            }
+
+            let bytes_left = (end as usize) - (ptr as usize);
+            let align_offset = (ptr as usize).next_multiple_of(layout.align()) - (ptr as usize);
+
+            if align_offset + layout.size() > bytes_left {
+                panic!("embassy-executor: task arena is full. You must increase the arena size, see the documentation for details: https://docs.embassy.dev/embassy-executor/");
+            }
+
+            let res = unsafe { ptr.add(align_offset) };
+            let ptr = unsafe { ptr.add(align_offset + layout.size()) };
+
+            self.ptr.borrow(cs).set(ptr);
+
+            unsafe { &mut *(res as *mut MaybeUninit<T>) }
+        }
+    }
+
+    static ARENA: Arena<{ crate::config::TASK_ARENA_SIZE }> = Arena::new();
+
+    pub struct TaskPoolRef {
+        // type-erased `&'static mut TaskPool<F, N>`
+        // Needed because statics can't have generics.
+        ptr: Mutex<Cell<*mut ()>>,
+    }
+    unsafe impl Sync for TaskPoolRef {}
+    unsafe impl Send for TaskPoolRef {}
+
+    impl TaskPoolRef {
+        pub const fn new() -> Self {
+            Self {
+                ptr: Mutex::new(Cell::new(null_mut())),
+            }
+        }
+
+        /// Get the pool for this ref, allocating it from the arena the first time.
+        ///
+        /// safety: for a given TaskPoolRef instance, must always call with the exact
+        /// same generic params.
+        pub unsafe fn get<F: Future, const N: usize>(&'static self) -> &'static TaskPool<F, N> {
+            critical_section::with(|cs| {
+                let ptr = self.ptr.borrow(cs);
+                if ptr.get().is_null() {
+                    let pool = ARENA.alloc::<TaskPool<F, N>>(cs);
+                    pool.write(TaskPool::new());
+                    ptr.set(pool as *mut _ as _);
+                }
+
+                unsafe { &*(ptr.get() as *const _) }
+            })
+        }
+    }
+}

vendor/embassy-executor/src/raw/mod.rs

@@ -0,0 +1,610 @@
+//! Raw executor.
+//!
+//! This module exposes "raw" Executor and Task structs for more low level control.
+//!
+//! ## WARNING: here be dragons!
+//!
+//! Using this module requires respecting subtle safety contracts. If you can, prefer using the safe
+//! [executor wrappers](crate::Executor) and the [`embassy_executor::task`](embassy_executor_macros::task) macro, which are fully safe.
+
+#[cfg_attr(target_has_atomic = "ptr", path = "run_queue_atomics.rs")]
+#[cfg_attr(not(target_has_atomic = "ptr"), path = "run_queue_critical_section.rs")]
+mod run_queue;
+
+#[cfg_attr(all(cortex_m, target_has_atomic = "8"), path = "state_atomics_arm.rs")]
+#[cfg_attr(all(not(cortex_m), target_has_atomic = "8"), path = "state_atomics.rs")]
+#[cfg_attr(not(target_has_atomic = "8"), path = "state_critical_section.rs")]
+mod state;
+
+#[cfg(feature = "integrated-timers")]
+mod timer_queue;
+pub(crate) mod util;
+#[cfg_attr(feature = "turbowakers", path = "waker_turbo.rs")]
+mod waker;
+
+use core::future::Future;
+use core::marker::PhantomData;
+use core::mem;
+use core::pin::Pin;
+use core::ptr::NonNull;
+use core::task::{Context, Poll};
+
+#[cfg(feature = "integrated-timers")]
+use embassy_time_driver::AlarmHandle;
+#[cfg(feature = "rtos-trace")]
+use rtos_trace::trace;
+
+use self::run_queue::{RunQueue, RunQueueItem};
+use self::state::State;
+use self::util::{SyncUnsafeCell, UninitCell};
+pub use self::waker::task_from_waker;
+use super::SpawnToken;
+
+/// Raw task header for use in task pointers.
+pub(crate) struct TaskHeader {
+    pub(crate) state: State,
+    pub(crate) run_queue_item: RunQueueItem,
+    pub(crate) executor: SyncUnsafeCell<Option<&'static SyncExecutor>>,
+    poll_fn: SyncUnsafeCell<Option<unsafe fn(TaskRef)>>,
+
+    #[cfg(feature = "integrated-timers")]
+    pub(crate) expires_at: SyncUnsafeCell<u64>,
+    #[cfg(feature = "integrated-timers")]
+    pub(crate) timer_queue_item: timer_queue::TimerQueueItem,
+}
+
+/// This is essentially a `&'static TaskStorage<F>` where the type of the future has been erased.
+#[derive(Clone, Copy)]
+pub struct TaskRef {
+    ptr: NonNull<TaskHeader>,
+}
+
+unsafe impl Send for TaskRef where &'static TaskHeader: Send {}
+unsafe impl Sync for TaskRef where &'static TaskHeader: Sync {}
+
+impl TaskRef {
+    fn new<F: Future + 'static>(task: &'static TaskStorage<F>) -> Self {
+        Self {
+            ptr: NonNull::from(task).cast(),
+        }
+    }
+
+    /// Safety: The pointer must have been obtained with `Task::as_ptr`
+    pub(crate) unsafe fn from_ptr(ptr: *const TaskHeader) -> Self {
+        Self {
+            ptr: NonNull::new_unchecked(ptr as *mut TaskHeader),
+        }
+    }
+
+    pub(crate) fn header(self) -> &'static TaskHeader {
+        unsafe { self.ptr.as_ref() }
+    }
+
+    /// The returned pointer is valid for the entire TaskStorage.
+    pub(crate) fn as_ptr(self) -> *const TaskHeader {
+        self.ptr.as_ptr()
+    }
+}
+
+/// Raw storage in which a task can be spawned.
+///
+/// This struct holds the necessary memory to spawn one task whose future is `F`.
+/// At a given time, the `TaskStorage` may be in spawned or not-spawned state. You
+/// may spawn it with [`TaskStorage::spawn()`], which will fail if it is already spawned.
+///
+/// A `TaskStorage` must live forever, it may not be deallocated even after the task has finished
+/// running. Hence the relevant methods require `&'static self`. It may be reused, however.
+///
+/// Internally, the [embassy_executor::task](embassy_executor_macros::task) macro allocates an array of `TaskStorage`s
+/// in a `static`. The most common reason to use the raw `Task` is to have control of where
+/// the memory for the task is allocated: on the stack, or on the heap with e.g. `Box::leak`, etc.
+
+// repr(C) is needed to guarantee that the Task is located at offset 0
+// This makes it safe to cast between TaskHeader and TaskStorage pointers.
+#[repr(C)]
+pub struct TaskStorage<F: Future + 'static> {
+    raw: TaskHeader,
+    future: UninitCell<F>, // Valid if STATE_SPAWNED
+}
+
+impl<F: Future + 'static> TaskStorage<F> {
+    const NEW: Self = Self::new();
+
+    /// Create a new TaskStorage, in not-spawned state.
+    pub const fn new() -> Self {
+        Self {
+            raw: TaskHeader {
+                state: State::new(),
+                run_queue_item: RunQueueItem::new(),
+                executor: SyncUnsafeCell::new(None),
+                // Note: this is lazily initialized so that a static `TaskStorage` will go in `.bss`
+                poll_fn: SyncUnsafeCell::new(None),
+
+                #[cfg(feature = "integrated-timers")]
+                expires_at: SyncUnsafeCell::new(0),
+                #[cfg(feature = "integrated-timers")]
+                timer_queue_item: timer_queue::TimerQueueItem::new(),
+            },
+            future: UninitCell::uninit(),
+        }
+    }
+
+    /// Try to spawn the task.
+    ///
+    /// The `future` closure constructs the future. It's only called if spawning is
+    /// actually possible. It is a closure instead of a simple `future: F` param to ensure
+    /// the future is constructed in-place, avoiding a temporary copy in the stack thanks to
+    /// NRVO optimizations.
+    ///
+    /// This function will fail if the task is already spawned and has not finished running.
+    /// In this case, the error is delayed: a "poisoned" SpawnToken is returned, which will
+    /// cause [`Spawner::spawn()`](super::Spawner::spawn) to return the error.
+    ///
+    /// Once the task has finished running, you may spawn it again. It is allowed to spawn it
+    /// on a different executor.
+    pub fn spawn(&'static self, future: impl FnOnce() -> F) -> SpawnToken<impl Sized> {
+        let task = AvailableTask::claim(self);
+        match task {
+            Some(task) => task.initialize(future),
+            None => SpawnToken::new_failed(),
+        }
+    }
+
+    unsafe fn poll(p: TaskRef) {
+        let this = &*(p.as_ptr() as *const TaskStorage<F>);
+
+        let future = Pin::new_unchecked(this.future.as_mut());
+        let waker = waker::from_task(p);
+        let mut cx = Context::from_waker(&waker);
+        match future.poll(&mut cx) {
+            Poll::Ready(_) => {
+                this.future.drop_in_place();
+                this.raw.state.despawn();
+
+                #[cfg(feature = "integrated-timers")]
+                this.raw.expires_at.set(u64::MAX);
+            }
+            Poll::Pending => {}
+        }
+
+        // the compiler is emitting a virtual call for waker drop, but we know
+        // it's a noop for our waker.
+        mem::forget(waker);
+    }
+
+    #[doc(hidden)]
+    #[allow(dead_code)]
+    fn _assert_sync(self) {
+        fn assert_sync<T: Sync>(_: T) {}
+
+        assert_sync(self)
+    }
+}
+
+/// An uninitialized [`TaskStorage`].
+pub struct AvailableTask<F: Future + 'static> {
+    task: &'static TaskStorage<F>,
+}
+
+impl<F: Future + 'static> AvailableTask<F> {
+    /// Try to claim a [`TaskStorage`].
+    ///
+    /// This function returns `None` if a task has already been spawned and has not finished running.
+    pub fn claim(task: &'static TaskStorage<F>) -> Option<Self> {
+        task.raw.state.spawn().then(|| Self { task })
+    }
+
+    fn initialize_impl<S>(self, future: impl FnOnce() -> F) -> SpawnToken<S> {
+        unsafe {
+            self.task.raw.poll_fn.set(Some(TaskStorage::<F>::poll));
+            self.task.future.write_in_place(future);
+
+            let task = TaskRef::new(self.task);
+
+            SpawnToken::new(task)
+        }
+    }
+
+    /// Initialize the [`TaskStorage`] to run the given future.
+    pub fn initialize(self, future: impl FnOnce() -> F) -> SpawnToken<F> {
+        self.initialize_impl::<F>(future)
+    }
+
+    /// Initialize the [`TaskStorage`] to run the given future.
+    ///
+    /// # Safety
+    ///
+    /// `future` must be a closure of the form `move || my_async_fn(args)`, where `my_async_fn`
+    /// is an `async fn`, NOT a hand-written `Future`.
+    #[doc(hidden)]
+    pub unsafe fn __initialize_async_fn<FutFn>(self, future: impl FnOnce() -> F) -> SpawnToken<FutFn> {
+        // When send-spawning a task, we construct the future in this thread, and effectively
+        // "send" it to the executor thread by enqueuing it in its queue. Therefore, in theory,
+        // send-spawning should require the future `F` to be `Send`.
+        //
+        // The problem is this is more restrictive than needed. Once the future is executing,
+        // it is never sent to another thread. It is only sent when spawning. It should be
+        // enough for the task's arguments to be Send. (and in practice it's super easy to
+        // accidentally make your futures !Send, for example by holding an `Rc` or a `&RefCell` across an `.await`.)
+        //
+        // We can do it by sending the task args and constructing the future in the executor thread
+        // on first poll. However, this cannot be done in-place, so it'll waste stack space for a copy
+        // of the args.
+        //
+        // Luckily, an `async fn` future contains just the args when freshly constructed. So, if the
+        // args are Send, it's OK to send a !Send future, as long as we do it before first polling it.
+        //
+        // (Note: this is how the generators are implemented today, it's not officially guaranteed yet,
+        // but it's possible it'll be guaranteed in the future. See zulip thread:
+        // https://rust-lang.zulipchat.com/#narrow/stream/187312-wg-async/topic/.22only.20before.20poll.22.20Send.20futures )
+        //
+        // The `FutFn` captures all the args, so if it's Send, the task can be send-spawned.
+        // This is why we return `SpawnToken<FutFn>` below.
+        //
+        // This ONLY holds for `async fn` futures. The other `spawn` methods can be called directly
+        // by the user, with arbitrary hand-implemented futures. This is why these return `SpawnToken<F>`.
+        self.initialize_impl::<FutFn>(future)
+    }
+}
+
+/// Raw storage that can hold up to N tasks of the same type.
+///
+/// This is essentially a `[TaskStorage<F>; N]`.
+pub struct TaskPool<F: Future + 'static, const N: usize> {
+    pool: [TaskStorage<F>; N],
+}
+
+impl<F: Future + 'static, const N: usize> TaskPool<F, N> {
+    /// Create a new TaskPool, with all tasks in non-spawned state.
+    pub const fn new() -> Self {
+        Self {
+            pool: [TaskStorage::NEW; N],
+        }
+    }
+
+    fn spawn_impl<T>(&'static self, future: impl FnOnce() -> F) -> SpawnToken<T> {
+        match self.pool.iter().find_map(AvailableTask::claim) {
+            Some(task) => task.initialize_impl::<T>(future),
+            None => SpawnToken::new_failed(),
+        }
+    }
+
+    /// Try to spawn a task in the pool.
+    ///
+    /// See [`TaskStorage::spawn()`] for details.
+    ///
+    /// This will loop over the pool and spawn the task in the first storage that
+    /// is currently free. If none is free, a "poisoned" SpawnToken is returned,
+    /// which will cause [`Spawner::spawn()`](super::Spawner::spawn) to return the error.
+    pub fn spawn(&'static self, future: impl FnOnce() -> F) -> SpawnToken<impl Sized> {
+        self.spawn_impl::<F>(future)
+    }
+
+    /// Like spawn(), but allows the task to be send-spawned if the args are Send even if
+    /// the future is !Send.
+    ///
+    /// Not covered by semver guarantees. DO NOT call this directly. Intended to be used
+    /// by the Embassy macros ONLY.
+    ///
+    /// SAFETY: `future` must be a closure of the form `move || my_async_fn(args)`, where `my_async_fn`
+    /// is an `async fn`, NOT a hand-written `Future`.
+    #[doc(hidden)]
+    pub unsafe fn _spawn_async_fn<FutFn>(&'static self, future: FutFn) -> SpawnToken<impl Sized>
+    where
+        FutFn: FnOnce() -> F,
+    {
+        // See the comment in AvailableTask::__initialize_async_fn for explanation.
+        self.spawn_impl::<FutFn>(future)
+    }
+}
+
+#[derive(Clone, Copy)]
+pub(crate) struct Pender(*mut ());
+
+unsafe impl Send for Pender {}
+unsafe impl Sync for Pender {}
+
+impl Pender {
+    pub(crate) fn pend(self) {
+        extern "Rust" {
+            fn __pender(context: *mut ());
+        }
+        unsafe { __pender(self.0) };
+    }
+}
+
+pub(crate) struct SyncExecutor {
+    run_queue: RunQueue,
+    pender: Pender,
+
+    #[cfg(feature = "integrated-timers")]
+    pub(crate) timer_queue: timer_queue::TimerQueue,
+    #[cfg(feature = "integrated-timers")]
+    alarm: AlarmHandle,
+}
+
+impl SyncExecutor {
+    pub(crate) fn new(pender: Pender) -> Self {
+        #[cfg(feature = "integrated-timers")]
+        let alarm = unsafe { unwrap!(embassy_time_driver::allocate_alarm()) };
+
+        Self {
+            run_queue: RunQueue::new(),
+            pender,
+
+            #[cfg(feature = "integrated-timers")]
+            timer_queue: timer_queue::TimerQueue::new(),
+            #[cfg(feature = "integrated-timers")]
+            alarm,
+        }
+    }
+
+    /// Enqueue a task in the task queue
+    ///
+    /// # Safety
+    /// - `task` must be a valid pointer to a spawned task.
+    /// - `task` must be set up to run in this executor.
+    /// - `task` must NOT be already enqueued (in this executor or another one).
+    #[inline(always)]
+    unsafe fn enqueue(&self, task: TaskRef) {
+        #[cfg(feature = "rtos-trace")]
+        trace::task_ready_begin(task.as_ptr() as u32);
+
+        if self.run_queue.enqueue(task) {
+            self.pender.pend();
+        }
+    }
+
+    #[cfg(feature = "integrated-timers")]
+    fn alarm_callback(ctx: *mut ()) {
+        let this: &Self = unsafe { &*(ctx as *const Self) };
+        this.pender.pend();
+    }
+
+    pub(super) unsafe fn spawn(&'static self, task: TaskRef) {
+        task.header().executor.set(Some(self));
+
+        #[cfg(feature = "rtos-trace")]
+        trace::task_new(task.as_ptr() as u32);
+
+        self.enqueue(task);
+    }
+
+    /// # Safety
+    ///
+    /// Same as [`Executor::poll`], plus you must only call this on the thread this executor was created.
+    pub(crate) unsafe fn poll(&'static self) {
+        #[cfg(feature = "integrated-timers")]
+        embassy_time_driver::set_alarm_callback(self.alarm, Self::alarm_callback, self as *const _ as *mut ());
+
+        #[allow(clippy::never_loop)]
+        loop {
+            #[cfg(feature = "integrated-timers")]
+            self.timer_queue
+                .dequeue_expired(embassy_time_driver::now(), wake_task_no_pend);
+
+            self.run_queue.dequeue_all(|p| {
+                let task = p.header();
+
+                #[cfg(feature = "integrated-timers")]
+                task.expires_at.set(u64::MAX);
+
+                if !task.state.run_dequeue() {
+                    // If task is not running, ignore it. This can happen in the following scenario:
+                    //   - Task gets dequeued, poll starts
+                    //   - While task is being polled, it gets woken. It gets placed in the queue.
+                    //   - Task poll finishes, returning done=true
+                    //   - RUNNING bit is cleared, but the task is already in the queue.
+                    return;
+                }
+
+                #[cfg(feature = "rtos-trace")]
+                trace::task_exec_begin(p.as_ptr() as u32);
+
+                // Run the task
+                task.poll_fn.get().unwrap_unchecked()(p);
+
+                #[cfg(feature = "rtos-trace")]
+                trace::task_exec_end();
+
+                // Enqueue or update into timer_queue
+                #[cfg(feature = "integrated-timers")]
+                self.timer_queue.update(p);
+            });
+
+            #[cfg(feature = "integrated-timers")]
+            {
+                // If this is already in the past, set_alarm might return false
+                // In that case do another poll loop iteration.
+                let next_expiration = self.timer_queue.next_expiration();
+                if embassy_time_driver::set_alarm(self.alarm, next_expiration) {
+                    break;
+                }
+            }
+
+            #[cfg(not(feature = "integrated-timers"))]
+            {
+                break;
+            }
+        }
+
+        #[cfg(feature = "rtos-trace")]
+        trace::system_idle();
+    }
+}
+
+/// Raw executor.
+///
+/// This is the core of the Embassy executor. It is low-level, requiring manual
+/// handling of wakeups and task polling. If you can, prefer using one of the
+/// [higher level executors](crate::Executor).
+///
+/// The raw executor leaves it up to you to handle wakeups and scheduling:
+///
+/// - To get the executor to do work, call `poll()`. This will poll all queued tasks (all tasks
+///   that "want to run").
+/// - You must supply a pender function, as shown below. The executor will call it to notify you
+///   it has work to do. You must arrange for `poll()` to be called as soon as possible.
+/// - Enabling `arch-xx` features will define a pender function for you. This means that you
+///   are limited to using the executors provided to you by the architecture/platform
+///   implementation. If you need a different executor, you must not enable `arch-xx` features.
+///
+/// The pender can be called from *any* context: any thread, any interrupt priority
+/// level, etc. It may be called synchronously from any `Executor` method call as well.
+/// You must deal with this correctly.
+///
+/// In particular, you must NOT call `poll` directly from the pender callback, as this violates
+/// the requirement for `poll` to not be called reentrantly.
+///
+/// The pender function must be exported with the name `__pender` and have the following signature:
+///
+/// ```rust
+/// #[export_name = "__pender"]
+/// fn pender(context: *mut ()) {
+///    // schedule `poll()` to be called
+/// }
+/// ```
+///
+/// The `context` argument is a piece of arbitrary data the executor will pass to the pender.
+/// You can set the `context` when calling [`Executor::new()`]. You can use it to, for example,
+/// differentiate between executors, or to pass a pointer to a callback that should be called.
+#[repr(transparent)]
+pub struct Executor {
+    pub(crate) inner: SyncExecutor,
+
+    _not_sync: PhantomData<*mut ()>,
+}
+
+impl Executor {
+    pub(crate) unsafe fn wrap(inner: &SyncExecutor) -> &Self {
+        mem::transmute(inner)
+    }
+
+    /// Create a new executor.
+    ///
+    /// When the executor has work to do, it will call the pender function and pass `context` to it.
+    ///
+    /// See [`Executor`] docs for details on the pender.
+    pub fn new(context: *mut ()) -> Self {
+        Self {
+            inner: SyncExecutor::new(Pender(context)),
+            _not_sync: PhantomData,
+        }
+    }
+
+    /// Spawn a task in this executor.
+    ///
+    /// # Safety
+    ///
+    /// `task` must be a valid pointer to an initialized but not-already-spawned task.
+    ///
+    /// It is OK to use `unsafe` to call this from a thread that's not the executor thread.
+    /// In this case, the task's Future must be Send. This is because this is effectively
+    /// sending the task to the executor thread.
+    pub(super) unsafe fn spawn(&'static self, task: TaskRef) {
+        self.inner.spawn(task)
+    }
+
+    /// Poll all queued tasks in this executor.
+    ///
+    /// This loops over all tasks that are queued to be polled (i.e. they're
+    /// freshly spawned or they've been woken). Other tasks are not polled.
+    ///
+    /// You must call `poll` after receiving a call to the pender. It is OK
+    /// to call `poll` even when not requested by the pender, but it wastes
+    /// energy.
+    ///
+    /// # Safety
+    ///
+    /// You must NOT call `poll` reentrantly on the same executor.
+    ///
+    /// In particular, note that `poll` may call the pender synchronously. Therefore, you
+    /// must NOT directly call `poll()` from the pender callback. Instead, the callback has to
+    /// somehow schedule for `poll()` to be called later, at a time you know for sure there's
+    /// no `poll()` already running.
+    pub unsafe fn poll(&'static self) {
+        self.inner.poll()
+    }
+
+    /// Get a spawner that spawns tasks in this executor.
+    ///
+    /// It is OK to call this method multiple times to obtain multiple
+    /// `Spawner`s. You may also copy `Spawner`s.
+    pub fn spawner(&'static self) -> super::Spawner {
+        super::Spawner::new(self)
+    }
+}
+
+/// Wake a task by `TaskRef`.
+///
+/// You can obtain a `TaskRef` from a `Waker` using [`task_from_waker`].
+pub fn wake_task(task: TaskRef) {
+    let header = task.header();
+    if header.state.run_enqueue() {
+        // We have just marked the task as scheduled, so enqueue it.
+        unsafe {
+            let executor = header.executor.get().unwrap_unchecked();
+            executor.enqueue(task);
+        }
+    }
+}
+
+/// Wake a task by `TaskRef` without calling pend.
+///
+/// You can obtain a `TaskRef` from a `Waker` using [`task_from_waker`].
+pub fn wake_task_no_pend(task: TaskRef) {
+    let header = task.header();
+    if header.state.run_enqueue() {
+        // We have just marked the task as scheduled, so enqueue it.
+        unsafe {
+            let executor = header.executor.get().unwrap_unchecked();
+            executor.run_queue.enqueue(task);
+        }
+    }
+}
+
+#[cfg(feature = "integrated-timers")]
+struct TimerQueue;
+
+#[cfg(feature = "integrated-timers")]
+impl embassy_time_queue_driver::TimerQueue for TimerQueue {
+    fn schedule_wake(&'static self, at: u64, waker: &core::task::Waker) {
+        let task = waker::task_from_waker(waker);
+        let task = task.header();
+        unsafe {
+            let expires_at = task.expires_at.get();
+            task.expires_at.set(expires_at.min(at));
+        }
+    }
+}
+
+#[cfg(feature = "integrated-timers")]
+embassy_time_queue_driver::timer_queue_impl!(static TIMER_QUEUE: TimerQueue = TimerQueue);
+
+#[cfg(all(feature = "rtos-trace", feature = "integrated-timers"))]
+const fn gcd(a: u64, b: u64) -> u64 {
+    if b == 0 {
+        a
+    } else {
+        gcd(b, a % b)
+    }
+}
+
+#[cfg(feature = "rtos-trace")]
+impl rtos_trace::RtosTraceOSCallbacks for Executor {
+    fn task_list() {
+        // We don't know what tasks exist, so we can't send them.
+    }
+    #[cfg(feature = "integrated-timers")]
+    fn time() -> u64 {
+        const GCD_1M: u64 = gcd(embassy_time_driver::TICK_HZ, 1_000_000);
+        embassy_time_driver::now() * (1_000_000 / GCD_1M) / (embassy_time_driver::TICK_HZ / GCD_1M)
+    }
+    #[cfg(not(feature = "integrated-timers"))]
+    fn time() -> u64 {
+        0
+    }
+}
+
+#[cfg(feature = "rtos-trace")]
+rtos_trace::global_os_callbacks! {Executor}

vendor/embassy-executor/src/raw/run_queue_atomics.rs

@@ -0,0 +1,87 @@
+use core::ptr;
+use core::ptr::NonNull;
+use core::sync::atomic::{AtomicPtr, Ordering};
+
+use super::{TaskHeader, TaskRef};
+use crate::raw::util::SyncUnsafeCell;
+
+pub(crate) struct RunQueueItem {
+    next: SyncUnsafeCell<Option<TaskRef>>,
+}
+
+impl RunQueueItem {
+    pub const fn new() -> Self {
+        Self {
+            next: SyncUnsafeCell::new(None),
+        }
+    }
+}
+
+/// Atomic task queue using a very, very simple lock-free linked-list queue:
+///
+/// To enqueue a task, task.next is set to the old head, and head is atomically set to task.
+///
+/// Dequeuing is done in batches: the queue is emptied by atomically replacing head with
+/// null. Then the batch is iterated following the next pointers until null is reached.
+///
+/// Note that batches will be iterated in the reverse order as they were enqueued. This is OK
+/// for our purposes: it can't create fairness problems since the next batch won't run until the
+/// current batch is completely processed, so even if a task enqueues itself instantly (for example
+/// by waking its own waker) can't prevent other tasks from running.
+pub(crate) struct RunQueue {
+    head: AtomicPtr<TaskHeader>,
+}
+
+impl RunQueue {
+    pub const fn new() -> Self {
+        Self {
+            head: AtomicPtr::new(ptr::null_mut()),
+        }
+    }
+
+    /// Enqueues an item. Returns true if the queue was empty.
+    ///
+    /// # Safety
+    ///
+    /// `item` must NOT be already enqueued in any queue.
+    #[inline(always)]
+    pub(crate) unsafe fn enqueue(&self, task: TaskRef) -> bool {
+        let mut was_empty = false;
+
+        self.head
+            .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |prev| {
+                was_empty = prev.is_null();
+                unsafe {
+                    // safety: the pointer is either null or valid
+                    let prev = NonNull::new(prev).map(|ptr| TaskRef::from_ptr(ptr.as_ptr()));
+                    // safety: there are no concurrent accesses to `next`
+                    task.header().run_queue_item.next.set(prev);
+                }
+                Some(task.as_ptr() as *mut _)
+            })
+            .ok();
+
+        was_empty
+    }
+
+    /// Empty the queue, then call `on_task` for each task that was in the queue.
+    /// NOTE: It is OK for `on_task` to enqueue more tasks. In this case they're left in the queue
+    /// and will be processed by the *next* call to `dequeue_all`, *not* the current one.
+    pub(crate) fn dequeue_all(&self, on_task: impl Fn(TaskRef)) {
+        // Atomically empty the queue.
+        let ptr = self.head.swap(ptr::null_mut(), Ordering::AcqRel);
+
+        // safety: the pointer is either null or valid
+        let mut next = unsafe { NonNull::new(ptr).map(|ptr| TaskRef::from_ptr(ptr.as_ptr())) };
+
+        // Iterate the linked list of tasks that were previously in the queue.
+        while let Some(task) = next {
+            // If the task re-enqueues itself, the `next` pointer will get overwritten.
+            // Therefore, first read the next pointer, and only then process the task.
+            // safety: there are no concurrent accesses to `next`
+            next = unsafe { task.header().run_queue_item.next.get() };
+
+            on_task(task);
+        }
+    }
+}

vendor/embassy-executor/src/raw/run_queue_critical_section.rs

@@ -0,0 +1,75 @@
+use core::cell::Cell;
+
+use critical_section::{CriticalSection, Mutex};
+
+use super::TaskRef;
+
+pub(crate) struct RunQueueItem {
+    next: Mutex<Cell<Option<TaskRef>>>,
+}
+
+impl RunQueueItem {
+    pub const fn new() -> Self {
+        Self {
+            next: Mutex::new(Cell::new(None)),
+        }
+    }
+}
+
+/// Atomic task queue using a very, very simple lock-free linked-list queue:
+///
+/// To enqueue a task, task.next is set to the old head, and head is atomically set to task.
+///
+/// Dequeuing is done in batches: the queue is emptied by atomically replacing head with
+/// null. Then the batch is iterated following the next pointers until null is reached.
+///
+/// Note that batches will be iterated in the reverse order as they were enqueued. This is OK
+/// for our purposes: it can't create fairness problems since the next batch won't run until the
+/// current batch is completely processed, so even if a task enqueues itself instantly (for example
+/// by waking its own waker) can't prevent other tasks from running.
+pub(crate) struct RunQueue {
+    head: Mutex<Cell<Option<TaskRef>>>,
+}
+
+impl RunQueue {
+    pub const fn new() -> Self {
+        Self {
+            head: Mutex::new(Cell::new(None)),
+        }
+    }
+
+    /// Enqueues an item. Returns true if the queue was empty.
+    ///
+    /// # Safety
+    ///
+    /// `item` must NOT be already enqueued in any queue.
+    #[inline(always)]
+    pub(crate) unsafe fn enqueue(&self, task: TaskRef) -> bool {
+        critical_section::with(|cs| {
+            let prev = self.head.borrow(cs).replace(Some(task));
+            task.header().run_queue_item.next.borrow(cs).set(prev);
+
+            prev.is_none()
+        })
+    }
+
+    /// Empty the queue, then call `on_task` for each task that was in the queue.
+    /// NOTE: It is OK for `on_task` to enqueue more tasks. In this case they're left in the queue
+    /// and will be processed by the *next* call to `dequeue_all`, *not* the current one.
+    pub(crate) fn dequeue_all(&self, on_task: impl Fn(TaskRef)) {
+        // Atomically empty the queue.
+        let mut next = critical_section::with(|cs| self.head.borrow(cs).take());
+
+        // Iterate the linked list of tasks that were previously in the queue.
+        while let Some(task) = next {
+            // If the task re-enqueues itself, the `next` pointer will get overwritten.
+            // Therefore, first read the next pointer, and only then process the task.
+
+            // safety: we know if the task is enqueued, no one else will touch the `next` pointer.
+            let cs = unsafe { CriticalSection::new() };
+            next = task.header().run_queue_item.next.borrow(cs).get();
+
+            on_task(task);
+        }
+    }
+}

vendor/embassy-executor/src/raw/state_atomics.rs

@@ -0,0 +1,73 @@
+use core::sync::atomic::{AtomicU32, Ordering};
+
+/// Task is spawned (has a future)
+pub(crate) const STATE_SPAWNED: u32 = 1 << 0;
+/// Task is in the executor run queue
+pub(crate) const STATE_RUN_QUEUED: u32 = 1 << 1;
+/// Task is in the executor timer queue
+#[cfg(feature = "integrated-timers")]
+pub(crate) const STATE_TIMER_QUEUED: u32 = 1 << 2;
+
+pub(crate) struct State {
+    state: AtomicU32,
+}
+
+impl State {
+    pub const fn new() -> State {
+        Self {
+            state: AtomicU32::new(0),
+        }
+    }
+
+    /// If task is idle, mark it as spawned + run_queued and return true.
+    #[inline(always)]
+    pub fn spawn(&self) -> bool {
+        self.state
+            .compare_exchange(0, STATE_SPAWNED | STATE_RUN_QUEUED, Ordering::AcqRel, Ordering::Acquire)
+            .is_ok()
+    }
+
+    /// Unmark the task as spawned.
+    #[inline(always)]
+    pub fn despawn(&self) {
+        self.state.fetch_and(!STATE_SPAWNED, Ordering::AcqRel);
+    }
+
+    /// Mark the task as run-queued if it's spawned and isn't already run-queued. Return true on success.
+    #[inline(always)]
+    pub fn run_enqueue(&self) -> bool {
+        self.state
+            .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |state| {
+                // If already scheduled, or if not started,
+                if (state & STATE_RUN_QUEUED != 0) || (state & STATE_SPAWNED == 0) {
+                    None
+                } else {
+                    // Mark it as scheduled
+                    Some(state | STATE_RUN_QUEUED)
+                }
+            })
+            .is_ok()
+    }
+
+    /// Unmark the task as run-queued. Return whether the task is spawned.
+    #[inline(always)]
+    pub fn run_dequeue(&self) -> bool {
+        let state = self.state.fetch_and(!STATE_RUN_QUEUED, Ordering::AcqRel);
+        state & STATE_SPAWNED != 0
+    }
+
+    /// Mark the task as timer-queued. Return whether it was newly queued (i.e. not queued before)
+    #[cfg(feature = "integrated-timers")]
+    #[inline(always)]
+    pub fn timer_enqueue(&self) -> bool {
+        let old_state = self.state.fetch_or(STATE_TIMER_QUEUED, Ordering::AcqRel);
+        old_state & STATE_TIMER_QUEUED == 0
+    }
+
+    /// Unmark the task as timer-queued.
+    #[cfg(feature = "integrated-timers")]
+    #[inline(always)]
+    pub fn timer_dequeue(&self) {
+        self.state.fetch_and(!STATE_TIMER_QUEUED, Ordering::AcqRel);
+    }
+}

vendor/embassy-executor/src/raw/state_atomics_arm.rs

@@ -0,0 +1,103 @@
+use core::arch::asm;
+use core::sync::atomic::{compiler_fence, AtomicBool, AtomicU32, Ordering};
+
+// Must be kept in sync with the layout of `State`!
+pub(crate) const STATE_SPAWNED: u32 = 1 << 0;
+pub(crate) const STATE_RUN_QUEUED: u32 = 1 << 8;
+
+#[repr(C, align(4))]
+pub(crate) struct State {
+    /// Task is spawned (has a future)
+    spawned: AtomicBool,
+    /// Task is in the executor run queue
+    run_queued: AtomicBool,
+    /// Task is in the executor timer queue
+    timer_queued: AtomicBool,
+    pad: AtomicBool,
+}
+
+impl State {
+    pub const fn new() -> State {
+        Self {
+            spawned: AtomicBool::new(false),
+            run_queued: AtomicBool::new(false),
+            timer_queued: AtomicBool::new(false),
+            pad: AtomicBool::new(false),
+        }
+    }
+
+    fn as_u32(&self) -> &AtomicU32 {
+        unsafe { &*(self as *const _ as *const AtomicU32) }
+    }
+
+    /// If task is idle, mark it as spawned + run_queued and return true.
+    #[inline(always)]
+    pub fn spawn(&self) -> bool {
+        compiler_fence(Ordering::Release);
+        let r = self
+            .as_u32()
+            .compare_exchange(
+                0,
+                STATE_SPAWNED | STATE_RUN_QUEUED,
+                Ordering::Relaxed,
+                Ordering::Relaxed,
+            )
+            .is_ok();
+        compiler_fence(Ordering::Acquire);
+        r
+    }
+
+    /// Unmark the task as spawned.
+    #[inline(always)]
+    pub fn despawn(&self) {
+        compiler_fence(Ordering::Release);
+        self.spawned.store(false, Ordering::Relaxed);
+    }
+
+    /// Mark the task as run-queued if it's spawned and isn't already run-queued. Return true on success.
+    #[inline(always)]
+    pub fn run_enqueue(&self) -> bool {
+        unsafe {
+            loop {
+                let state: u32;
+                asm!("ldrex {}, [{}]", out(reg) state, in(reg) self, options(nostack));
+
+                if (state & STATE_RUN_QUEUED != 0) || (state & STATE_SPAWNED == 0) {
+                    asm!("clrex", options(nomem, nostack));
+                    return false;
+                }
+
+                let outcome: usize;
+                let new_state = state | STATE_RUN_QUEUED;
+                asm!("strex {}, {}, [{}]", out(reg) outcome, in(reg) new_state, in(reg) self, options(nostack));
+                if outcome == 0 {
+                    return true;
+                }
+            }
+        }
+    }
+
+    /// Unmark the task as run-queued. Return whether the task is spawned.
+    #[inline(always)]
+    pub fn run_dequeue(&self) -> bool {
+        compiler_fence(Ordering::Release);
+
+        let r = self.spawned.load(Ordering::Relaxed);
+        self.run_queued.store(false, Ordering::Relaxed);
+        r
+    }
+
+    /// Mark the task as timer-queued. Return whether it was newly queued (i.e. not queued before)
+    #[cfg(feature = "integrated-timers")]
+    #[inline(always)]
+    pub fn timer_enqueue(&self) -> bool {
+        !self.timer_queued.swap(true, Ordering::Relaxed)
+    }
+
+    /// Unmark the task as timer-queued.
+    #[cfg(feature = "integrated-timers")]
+    #[inline(always)]
+    pub fn timer_dequeue(&self) {
+        self.timer_queued.store(false, Ordering::Relaxed);
+    }
+}

vendor/embassy-executor/src/raw/state_critical_section.rs

@@ -0,0 +1,93 @@
+use core::cell::Cell;
+
+use critical_section::Mutex;
+
+/// Task is spawned (has a future)
+pub(crate) const STATE_SPAWNED: u32 = 1 << 0;
+/// Task is in the executor run queue
+pub(crate) const STATE_RUN_QUEUED: u32 = 1 << 1;
+/// Task is in the executor timer queue
+#[cfg(feature = "integrated-timers")]
+pub(crate) const STATE_TIMER_QUEUED: u32 = 1 << 2;
+
+pub(crate) struct State {
+    state: Mutex<Cell<u32>>,
+}
+
+impl State {
+    pub const fn new() -> State {
+        Self {
+            state: Mutex::new(Cell::new(0)),
+        }
+    }
+
+    fn update<R>(&self, f: impl FnOnce(&mut u32) -> R) -> R {
+        critical_section::with(|cs| {
+            let s = self.state.borrow(cs);
+            let mut val = s.get();
+            let r = f(&mut val);
+            s.set(val);
+            r
+        })
+    }
+
+    /// If task is idle, mark it as spawned + run_queued and return true.
+    #[inline(always)]
+    pub fn spawn(&self) -> bool {
+        self.update(|s| {
+            if *s == 0 {
+                *s = STATE_SPAWNED | STATE_RUN_QUEUED;
+                true
+            } else {
+                false
+            }
+        })
+    }
+
+    /// Unmark the task as spawned.
+    #[inline(always)]
+    pub fn despawn(&self) {
+        self.update(|s| *s &= !STATE_SPAWNED);
+    }
+
+    /// Mark the task as run-queued if it's spawned and isn't already run-queued. Return true on success.
+    #[inline(always)]
+    pub fn run_enqueue(&self) -> bool {
+        self.update(|s| {
+            if (*s & STATE_RUN_QUEUED != 0) || (*s & STATE_SPAWNED == 0) {
+                false
+            } else {
+                *s |= STATE_RUN_QUEUED;
+                true
+            }
+        })
+    }
+
+    /// Unmark the task as run-queued. Return whether the task is spawned.
+    #[inline(always)]
+    pub fn run_dequeue(&self) -> bool {
+        self.update(|s| {
+            let ok = *s & STATE_SPAWNED != 0;
+            *s &= !STATE_RUN_QUEUED;
+            ok
+        })
+    }
+
+    /// Mark the task as timer-queued. Return whether it was newly queued (i.e. not queued before)
+    #[cfg(feature = "integrated-timers")]
+    #[inline(always)]
+    pub fn timer_enqueue(&self) -> bool {
+        self.update(|s| {
+            let ok = *s & STATE_TIMER_QUEUED == 0;
+            *s |= STATE_TIMER_QUEUED;
+            ok
+        })
+    }
+
+    /// Unmark the task as timer-queued.
+    #[cfg(feature = "integrated-timers")]
+    #[inline(always)]
+    pub fn timer_dequeue(&self) {
+        self.update(|s| *s &= !STATE_TIMER_QUEUED);
+    }
+}

vendor/embassy-executor/src/raw/timer_queue.rs

@@ -0,0 +1,76 @@
+use core::cmp::min;
+
+use super::TaskRef;
+use crate::raw::util::SyncUnsafeCell;
+
+pub(crate) struct TimerQueueItem {
+    next: SyncUnsafeCell<Option<TaskRef>>,
+}
+
+impl TimerQueueItem {
+    pub const fn new() -> Self {
+        Self {
+            next: SyncUnsafeCell::new(None),
+        }
+    }
+}
+
+pub(crate) struct TimerQueue {
+    head: SyncUnsafeCell<Option<TaskRef>>,
+}
+
+impl TimerQueue {
+    pub const fn new() -> Self {
+        Self {
+            head: SyncUnsafeCell::new(None),
+        }
+    }
+
+    pub(crate) unsafe fn update(&self, p: TaskRef) {
+        let task = p.header();
+        if task.expires_at.get() != u64::MAX {
+            if task.state.timer_enqueue() {
+                task.timer_queue_item.next.set(self.head.get());
+                self.head.set(Some(p));
+            }
+        }
+    }
+
+    pub(crate) unsafe fn next_expiration(&self) -> u64 {
+        let mut res = u64::MAX;
+        self.retain(|p| {
+            let task = p.header();
+            let expires = task.expires_at.get();
+            res = min(res, expires);
+            expires != u64::MAX
+        });
+        res
+    }
+
+    pub(crate) unsafe fn dequeue_expired(&self, now: u64, on_task: impl Fn(TaskRef)) {
+        self.retain(|p| {
+            let task = p.header();
+            if task.expires_at.get() <= now {
+                on_task(p);
+                false
+            } else {
+                true
+            }
+        });
+    }
+
+    pub(crate) unsafe fn retain(&self, mut f: impl FnMut(TaskRef) -> bool) {
+        let mut prev = &self.head;
+        while let Some(p) = prev.get() {
+            let task = p.header();
+            if f(p) {
+                // Skip to next
+                prev = &task.timer_queue_item.next;
+            } else {
+                // Remove it
+                prev.set(task.timer_queue_item.next.get());
+                task.state.timer_dequeue();
+            }
+        }
+    }
+}

vendor/embassy-executor/src/raw/util.rs

@@ -0,0 +1,57 @@
+use core::cell::UnsafeCell;
+use core::mem::MaybeUninit;
+use core::ptr;
+
+pub(crate) struct UninitCell<T>(MaybeUninit<UnsafeCell<T>>);
+impl<T> UninitCell<T> {
+    pub const fn uninit() -> Self {
+        Self(MaybeUninit::uninit())
+    }
+
+    pub unsafe fn as_mut_ptr(&self) -> *mut T {
+        (*self.0.as_ptr()).get()
+    }
+
+    #[allow(clippy::mut_from_ref)]
+    pub unsafe fn as_mut(&self) -> &mut T {
+        &mut *self.as_mut_ptr()
+    }
+
+    #[inline(never)]
+    pub unsafe fn write_in_place(&self, func: impl FnOnce() -> T) {
+        ptr::write(self.as_mut_ptr(), func())
+    }
+
+    pub unsafe fn drop_in_place(&self) {
+        ptr::drop_in_place(self.as_mut_ptr())
+    }
+}
+
+unsafe impl<T> Sync for UninitCell<T> {}
+
+#[repr(transparent)]
+pub struct SyncUnsafeCell<T> {
+    value: UnsafeCell<T>,
+}
+
+unsafe impl<T: Sync> Sync for SyncUnsafeCell<T> {}
+
+impl<T> SyncUnsafeCell<T> {
+    #[inline]
+    pub const fn new(value: T) -> Self {
+        Self {
+            value: UnsafeCell::new(value),
+        }
+    }
+
+    pub unsafe fn set(&self, value: T) {
+        *self.value.get() = value;
+    }
+
+    pub unsafe fn get(&self) -> T
+    where
+        T: Copy,
+    {
+        *self.value.get()
+    }
+}

vendor/embassy-executor/src/raw/waker.rs

@@ -0,0 +1,53 @@
+use core::task::{RawWaker, RawWakerVTable, Waker};
+
+use super::{wake_task, TaskHeader, TaskRef};
+
+static VTABLE: RawWakerVTable = RawWakerVTable::new(clone, wake, wake, drop);
+
+unsafe fn clone(p: *const ()) -> RawWaker {
+    RawWaker::new(p, &VTABLE)
+}
+
+unsafe fn wake(p: *const ()) {
+    wake_task(TaskRef::from_ptr(p as *const TaskHeader))
+}
+
+unsafe fn drop(_: *const ()) {
+    // nop
+}
+
+pub(crate) unsafe fn from_task(p: TaskRef) -> Waker {
+    Waker::from_raw(RawWaker::new(p.as_ptr() as _, &VTABLE))
+}
+
+/// Get a task pointer from a waker.
+///
+/// This can be used as an optimization in wait queues to store task pointers
+/// (1 word) instead of full Wakers (2 words). This saves a bit of RAM and helps
+/// avoid dynamic dispatch.
+///
+/// You can use the returned task pointer to wake the task with [`wake_task`](super::wake_task).
+///
+/// # Panics
+///
+/// Panics if the waker is not created by the Embassy executor.
+pub fn task_from_waker(waker: &Waker) -> TaskRef {
+    struct WakerHack {
+        data: *const (),
+        vtable: &'static RawWakerVTable,
+    }
+
+    // safety: OK because WakerHack has the same layout as Waker.
+    // This is not really guaranteed because the structs are `repr(Rust)`, it is
+    // indeed the case in the current implementation.
+    // TODO use waker_getters when stable. https://github.com/rust-lang/rust/issues/96992
+    let hack: &WakerHack = unsafe { core::mem::transmute(waker) };
+
+    // make sure to compare vtable addresses. Doing `==` on the references
+    // will compare the contents, which is slower.
+    if hack.vtable as *const _ != &VTABLE as *const _ {
+        panic!("Found waker not created by the Embassy executor. `embassy_time::Timer` only works with the Embassy executor.")
+    }
+    // safety: our wakers are always created with `TaskRef::as_ptr`
+    unsafe { TaskRef::from_ptr(hack.data as *const TaskHeader) }
+}

vendor/embassy-executor/src/raw/waker_turbo.rs

@@ -0,0 +1,34 @@
+use core::ptr::NonNull;
+use core::task::Waker;
+
+use super::{wake_task, TaskHeader, TaskRef};
+
+pub(crate) unsafe fn from_task(p: TaskRef) -> Waker {
+    Waker::from_turbo_ptr(NonNull::new_unchecked(p.as_ptr() as _))
+}
+
+/// Get a task pointer from a waker.
+///
+/// This can be used as an optimization in wait queues to store task pointers
+/// (1 word) instead of full Wakers (2 words). This saves a bit of RAM and helps
+/// avoid dynamic dispatch.
+///
+/// You can use the returned task pointer to wake the task with [`wake_task`](super::wake_task).
+///
+/// # Panics
+///
+/// Panics if the waker is not created by the Embassy executor.
+pub fn task_from_waker(waker: &Waker) -> TaskRef {
+    let ptr = waker.as_turbo_ptr().as_ptr();
+
+    // safety: our wakers are always created with `TaskRef::as_ptr`
+    unsafe { TaskRef::from_ptr(ptr as *const TaskHeader) }
+}
+
+#[inline(never)]
+#[no_mangle]
+fn _turbo_wake(ptr: NonNull<()>) {
+    // safety: our wakers are always created with `TaskRef::as_ptr`
+    let task = unsafe { TaskRef::from_ptr(ptr.as_ptr() as *const TaskHeader) };
+    wake_task(task)
+}

vendor/embassy-executor/src/spawner.rs

@@ -0,0 +1,197 @@
+use core::future::poll_fn;
+use core::marker::PhantomData;
+use core::mem;
+use core::task::Poll;
+
+use super::raw;
+
+/// Token to spawn a newly-created task in an executor.
+///
+/// When calling a task function (like `#[embassy_executor::task] async fn my_task() { ... }`), the returned
+/// value is a `SpawnToken` that represents an instance of the task, ready to spawn. You must
+/// then spawn it into an executor, typically with [`Spawner::spawn()`].
+///
+/// The generic parameter `S` determines whether the task can be spawned in executors
+/// in other threads or not. If `S: Send`, it can, which allows spawning it into a [`SendSpawner`].
+/// If not, it can't, so it can only be spawned into the current thread's executor, with [`Spawner`].
+///
+/// # Panics
+///
+/// Dropping a SpawnToken instance panics. You may not "abort" spawning a task in this way.
+/// Once you've invoked a task function and obtained a SpawnToken, you *must* spawn it.
+#[must_use = "Calling a task function does nothing on its own. You must spawn the returned SpawnToken, typically with Spawner::spawn()"]
+pub struct SpawnToken<S> {
+    raw_task: Option<raw::TaskRef>,
+    phantom: PhantomData<*mut S>,
+}
+
+impl<S> SpawnToken<S> {
+    pub(crate) unsafe fn new(raw_task: raw::TaskRef) -> Self {
+        Self {
+            raw_task: Some(raw_task),
+            phantom: PhantomData,
+        }
+    }
+
+    /// Return a SpawnToken that represents a failed spawn.
+    pub fn new_failed() -> Self {
+        Self {
+            raw_task: None,
+            phantom: PhantomData,
+        }
+    }
+}
+
+impl<S> Drop for SpawnToken<S> {
+    fn drop(&mut self) {
+        // TODO deallocate the task instead.
+        panic!("SpawnToken instances may not be dropped. You must pass them to Spawner::spawn()")
+    }
+}
+
+/// Error returned when spawning a task.
+#[derive(Copy, Clone, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum SpawnError {
+    /// Too many instances of this task are already running.
+    ///
+    /// By default, a task marked with `#[embassy_executor::task]` can only have one instance
+    /// running at a time. You may allow multiple instances to run in parallel with
+    /// `#[embassy_executor::task(pool_size = 4)]`, at the cost of higher RAM usage.
+    Busy,
+}
+
+/// Handle to spawn tasks into an executor.
+///
+/// This Spawner can spawn any task (Send and non-Send ones), but it can
+/// only be used in the executor thread (it is not Send itself).
+///
+/// If you want to spawn tasks from another thread, use [SendSpawner].
+#[derive(Copy, Clone)]
+pub struct Spawner {
+    executor: &'static raw::Executor,
+    not_send: PhantomData<*mut ()>,
+}
+
+impl Spawner {
+    pub(crate) fn new(executor: &'static raw::Executor) -> Self {
+        Self {
+            executor,
+            not_send: PhantomData,
+        }
+    }
+
+    /// Get a Spawner for the current executor.
+    ///
+    /// This function is `async` just to get access to the current async
+    /// context. It returns instantly, it does not block/yield.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the current executor is not an Embassy executor.
+    pub async fn for_current_executor() -> Self {
+        poll_fn(|cx| {
+            let task = raw::task_from_waker(cx.waker());
+            let executor = unsafe { task.header().executor.get().unwrap_unchecked() };
+            let executor = unsafe { raw::Executor::wrap(executor) };
+            Poll::Ready(Self::new(executor))
+        })
+        .await
+    }
+
+    /// Spawn a task into an executor.
+    ///
+    /// You obtain the `token` by calling a task function (i.e. one marked with `#[embassy_executor::task]`).
+    pub fn spawn<S>(&self, token: SpawnToken<S>) -> Result<(), SpawnError> {
+        let task = token.raw_task;
+        mem::forget(token);
+
+        match task {
+            Some(task) => {
+                unsafe { self.executor.spawn(task) };
+                Ok(())
+            }
+            None => Err(SpawnError::Busy),
+        }
+    }
+
+    // Used by the `embassy_executor_macros::main!` macro to throw an error when spawn
+    // fails. This is here to allow conditional use of `defmt::unwrap!`
+    // without introducing a `defmt` feature in the `embassy_executor_macros` package,
+    // which would require use of `-Z namespaced-features`.
+    /// Spawn a task into an executor, panicking on failure.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the spawning fails.
+    pub fn must_spawn<S>(&self, token: SpawnToken<S>) {
+        unwrap!(self.spawn(token));
+    }
+
+    /// Convert this Spawner to a SendSpawner. This allows you to send the
+    /// spawner to other threads, but the spawner loses the ability to spawn
+    /// non-Send tasks.
+    pub fn make_send(&self) -> SendSpawner {
+        SendSpawner::new(&self.executor.inner)
+    }
+}
+
+/// Handle to spawn tasks into an executor from any thread.
+///
+/// This Spawner can be used from any thread (it is Send), but it can
+/// only spawn Send tasks. The reason for this is spawning is effectively
+/// "sending" the tasks to the executor thread.
+///
+/// If you want to spawn non-Send tasks, use [Spawner].
+#[derive(Copy, Clone)]
+pub struct SendSpawner {
+    executor: &'static raw::SyncExecutor,
+}
+
+impl SendSpawner {
+    pub(crate) fn new(executor: &'static raw::SyncExecutor) -> Self {
+        Self { executor }
+    }
+
+    /// Get a Spawner for the current executor.
+    ///
+    /// This function is `async` just to get access to the current async
+    /// context. It returns instantly, it does not block/yield.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the current executor is not an Embassy executor.
+    pub async fn for_current_executor() -> Self {
+        poll_fn(|cx| {
+            let task = raw::task_from_waker(cx.waker());
+            let executor = unsafe { task.header().executor.get().unwrap_unchecked() };
+            Poll::Ready(Self::new(executor))
+        })
+        .await
+    }
+
+    /// Spawn a task into an executor.
+    ///
+    /// You obtain the `token` by calling a task function (i.e. one marked with `#[embassy_executor::task]`).
+    pub fn spawn<S: Send>(&self, token: SpawnToken<S>) -> Result<(), SpawnError> {
+        let header = token.raw_task;
+        mem::forget(token);
+
+        match header {
+            Some(header) => {
+                unsafe { self.executor.spawn(header) };
+                Ok(())
+            }
+            None => Err(SpawnError::Busy),
+        }
+    }
+
+    /// Spawn a task into an executor, panicking on failure.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the spawning fails.
+    pub fn must_spawn<S: Send>(&self, token: SpawnToken<S>) {
+        unwrap!(self.spawn(token));
+    }
+}