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-nrf/src/pdm.rs

@@ -0,0 +1,494 @@
+//! Pulse Density Modulation (PDM) microphone driver
+
+#![macro_use]
+
+use core::future::poll_fn;
+use core::marker::PhantomData;
+use core::sync::atomic::{compiler_fence, Ordering};
+use core::task::Poll;
+
+use embassy_hal_internal::drop::OnDrop;
+use embassy_hal_internal::{into_ref, PeripheralRef};
+use embassy_sync::waitqueue::AtomicWaker;
+use fixed::types::I7F1;
+
+use crate::chip::EASY_DMA_SIZE;
+use crate::gpio::{AnyPin, Pin as GpioPin, SealedPin};
+use crate::interrupt::typelevel::Interrupt;
+use crate::pac::pdm::mode::{EDGE_A, OPERATION_A};
+pub use crate::pac::pdm::pdmclkctrl::FREQ_A as Frequency;
+#[cfg(any(
+    feature = "nrf52840",
+    feature = "nrf52833",
+    feature = "_nrf5340-app",
+    feature = "_nrf91",
+))]
+pub use crate::pac::pdm::ratio::RATIO_A as Ratio;
+use crate::{interrupt, Peripheral};
+
+/// Interrupt handler
+pub struct InterruptHandler<T: Instance> {
+    _phantom: PhantomData<T>,
+}
+
+impl<T: Instance> interrupt::typelevel::Handler<T::Interrupt> for InterruptHandler<T> {
+    unsafe fn on_interrupt() {
+        let r = T::regs();
+
+        if r.events_end.read().bits() != 0 {
+            r.intenclr.write(|w| w.end().clear());
+        }
+
+        if r.events_started.read().bits() != 0 {
+            r.intenclr.write(|w| w.started().clear());
+        }
+
+        if r.events_stopped.read().bits() != 0 {
+            r.intenclr.write(|w| w.stopped().clear());
+        }
+
+        T::state().waker.wake();
+    }
+}
+
+/// PDM microphone interface
+pub struct Pdm<'d, T: Instance> {
+    _peri: PeripheralRef<'d, T>,
+}
+
+/// PDM error
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[non_exhaustive]
+pub enum Error {
+    /// Buffer is too long
+    BufferTooLong,
+    /// Buffer is empty
+    BufferZeroLength,
+    /// PDM is not running
+    NotRunning,
+    /// PDM is already running
+    AlreadyRunning,
+}
+
+static DUMMY_BUFFER: [i16; 1] = [0; 1];
+
+/// The state of a continuously running sampler. While it reflects
+/// the progress of a sampler, it also signals what should be done
+/// next. For example, if the sampler has stopped then the PDM implementation
+/// can then tear down its infrastructure
+#[derive(PartialEq)]
+pub enum SamplerState {
+    /// The sampler processed the samples and is ready for more
+    Sampled,
+    /// The sampler is done processing samples
+    Stopped,
+}
+
+impl<'d, T: Instance> Pdm<'d, T> {
+    /// Create PDM driver
+    pub fn new(
+        pdm: impl Peripheral<P = T> + 'd,
+        _irq: impl interrupt::typelevel::Binding<T::Interrupt, InterruptHandler<T>> + 'd,
+        clk: impl Peripheral<P = impl GpioPin> + 'd,
+        din: impl Peripheral<P = impl GpioPin> + 'd,
+        config: Config,
+    ) -> Self {
+        into_ref!(pdm, clk, din);
+        Self::new_inner(pdm, clk.map_into(), din.map_into(), config)
+    }
+
+    fn new_inner(
+        pdm: PeripheralRef<'d, T>,
+        clk: PeripheralRef<'d, AnyPin>,
+        din: PeripheralRef<'d, AnyPin>,
+        config: Config,
+    ) -> Self {
+        into_ref!(pdm);
+
+        let r = T::regs();
+
+        // setup gpio pins
+        din.conf().write(|w| w.input().set_bit());
+        r.psel.din.write(|w| unsafe { w.bits(din.psel_bits()) });
+        clk.set_low();
+        clk.conf().write(|w| w.dir().output());
+        r.psel.clk.write(|w| unsafe { w.bits(clk.psel_bits()) });
+
+        // configure
+        r.pdmclkctrl.write(|w| w.freq().variant(config.frequency));
+        #[cfg(any(
+            feature = "nrf52840",
+            feature = "nrf52833",
+            feature = "_nrf5340-app",
+            feature = "_nrf91",
+        ))]
+        r.ratio.write(|w| w.ratio().variant(config.ratio));
+        r.mode.write(|w| {
+            w.operation().variant(config.operation_mode.into());
+            w.edge().variant(config.edge.into());
+            w
+        });
+
+        Self::_set_gain(r, config.gain_left, config.gain_right);
+
+        // Disable all events interrupts
+        r.intenclr.write(|w| unsafe { w.bits(0x003F_FFFF) });
+
+        // IRQ
+        T::Interrupt::unpend();
+        unsafe { T::Interrupt::enable() };
+
+        r.enable.write(|w| w.enable().set_bit());
+
+        Self { _peri: pdm }
+    }
+
+    fn _set_gain(r: &crate::pac::pdm::RegisterBlock, gain_left: I7F1, gain_right: I7F1) {
+        let gain_to_bits = |gain: I7F1| -> u8 {
+            let gain = gain.saturating_add(I7F1::from_bits(0x28)).to_bits().clamp(0, 0x50);
+            unsafe { core::mem::transmute(gain) }
+        };
+        let gain_left = gain_to_bits(gain_left);
+        let gain_right = gain_to_bits(gain_right);
+        r.gainl.write(|w| unsafe { w.gainl().bits(gain_left) });
+        r.gainr.write(|w| unsafe { w.gainr().bits(gain_right) });
+    }
+
+    /// Adjust the gain of the PDM microphone on the fly
+    pub fn set_gain(&mut self, gain_left: I7F1, gain_right: I7F1) {
+        Self::_set_gain(T::regs(), gain_left, gain_right)
+    }
+
+    /// Start sampling microphone data into a dummy buffer.
+    /// Useful to start the microphone and keep it active between recording samples.
+    pub async fn start(&mut self) {
+        let r = T::regs();
+
+        // start dummy sampling because microphone needs some setup time
+        r.sample
+            .ptr
+            .write(|w| unsafe { w.sampleptr().bits(DUMMY_BUFFER.as_ptr() as u32) });
+        r.sample
+            .maxcnt
+            .write(|w| unsafe { w.buffsize().bits(DUMMY_BUFFER.len() as _) });
+
+        r.tasks_start.write(|w| unsafe { w.bits(1) });
+    }
+
+    /// Stop sampling microphone data inta a dummy buffer
+    pub async fn stop(&mut self) {
+        let r = T::regs();
+        r.tasks_stop.write(|w| unsafe { w.bits(1) });
+        r.events_started.reset();
+    }
+
+    /// Sample data into the given buffer
+    pub async fn sample(&mut self, buffer: &mut [i16]) -> Result<(), Error> {
+        if buffer.is_empty() {
+            return Err(Error::BufferZeroLength);
+        }
+        if buffer.len() > EASY_DMA_SIZE {
+            return Err(Error::BufferTooLong);
+        }
+
+        let r = T::regs();
+
+        if r.events_started.read().bits() == 0 {
+            return Err(Error::NotRunning);
+        }
+
+        let drop = OnDrop::new(move || {
+            r.intenclr.write(|w| w.end().clear());
+            r.events_stopped.reset();
+
+            // reset to dummy buffer
+            r.sample
+                .ptr
+                .write(|w| unsafe { w.sampleptr().bits(DUMMY_BUFFER.as_ptr() as u32) });
+            r.sample
+                .maxcnt
+                .write(|w| unsafe { w.buffsize().bits(DUMMY_BUFFER.len() as _) });
+
+            while r.events_stopped.read().bits() == 0 {}
+        });
+
+        // setup user buffer
+        let ptr = buffer.as_ptr();
+        let len = buffer.len();
+        r.sample.ptr.write(|w| unsafe { w.sampleptr().bits(ptr as u32) });
+        r.sample.maxcnt.write(|w| unsafe { w.buffsize().bits(len as _) });
+
+        // wait till the current sample is finished and the user buffer sample is started
+        Self::wait_for_sample().await;
+
+        // reset the buffer back to the dummy buffer
+        r.sample
+            .ptr
+            .write(|w| unsafe { w.sampleptr().bits(DUMMY_BUFFER.as_ptr() as u32) });
+        r.sample
+            .maxcnt
+            .write(|w| unsafe { w.buffsize().bits(DUMMY_BUFFER.len() as _) });
+
+        // wait till the user buffer is sampled
+        Self::wait_for_sample().await;
+
+        drop.defuse();
+
+        Ok(())
+    }
+
+    async fn wait_for_sample() {
+        let r = T::regs();
+
+        r.events_end.reset();
+        r.intenset.write(|w| w.end().set());
+
+        compiler_fence(Ordering::SeqCst);
+
+        poll_fn(|cx| {
+            T::state().waker.register(cx.waker());
+            if r.events_end.read().bits() != 0 {
+                return Poll::Ready(());
+            }
+            Poll::Pending
+        })
+        .await;
+
+        compiler_fence(Ordering::SeqCst);
+    }
+
+    /// Continuous sampling with double buffers.
+    ///
+    /// A sampler closure is provided that receives the buffer of samples, noting
+    /// that the size of this buffer can be less than the original buffer's size.
+    /// A command is return from the closure that indicates whether the sampling
+    /// should continue or stop.
+    ///
+    /// NOTE: The time spent within the callback supplied should not exceed the time
+    /// taken to acquire the samples into a single buffer. You should measure the
+    /// time taken by the callback and set the sample buffer size accordingly.
+    /// Exceeding this time can lead to samples becoming dropped.
+    pub async fn run_task_sampler<S, const N: usize>(
+        &mut self,
+        bufs: &mut [[i16; N]; 2],
+        mut sampler: S,
+    ) -> Result<(), Error>
+    where
+        S: FnMut(&[i16; N]) -> SamplerState,
+    {
+        let r = T::regs();
+
+        if r.events_started.read().bits() != 0 {
+            return Err(Error::AlreadyRunning);
+        }
+
+        r.sample
+            .ptr
+            .write(|w| unsafe { w.sampleptr().bits(bufs[0].as_mut_ptr() as u32) });
+        r.sample.maxcnt.write(|w| unsafe { w.buffsize().bits(N as _) });
+
+        // Reset and enable the events
+        r.events_end.reset();
+        r.events_started.reset();
+        r.events_stopped.reset();
+        r.intenset.write(|w| {
+            w.end().set();
+            w.started().set();
+            w.stopped().set();
+            w
+        });
+
+        // Don't reorder the start event before the previous writes. Hopefully self
+        // wouldn't happen anyway
+        compiler_fence(Ordering::SeqCst);
+
+        r.tasks_start.write(|w| unsafe { w.bits(1) });
+
+        let mut current_buffer = 0;
+
+        let mut done = false;
+
+        let drop = OnDrop::new(|| {
+            r.tasks_stop.write(|w| unsafe { w.bits(1) });
+            // N.B. It would be better if this were async, but Drop only support sync code
+            while r.events_stopped.read().bits() != 0 {}
+        });
+
+        // Wait for events and complete when the sampler indicates it has had enough
+        poll_fn(|cx| {
+            let r = T::regs();
+
+            T::state().waker.register(cx.waker());
+
+            if r.events_end.read().bits() != 0 {
+                compiler_fence(Ordering::SeqCst);
+
+                r.events_end.reset();
+                r.intenset.write(|w| w.end().set());
+
+                if !done {
+                    // Discard the last buffer after the user requested a stop
+                    if sampler(&bufs[current_buffer]) == SamplerState::Sampled {
+                        let next_buffer = 1 - current_buffer;
+                        current_buffer = next_buffer;
+                    } else {
+                        r.tasks_stop.write(|w| unsafe { w.bits(1) });
+                        done = true;
+                    };
+                };
+            }
+
+            if r.events_started.read().bits() != 0 {
+                r.events_started.reset();
+                r.intenset.write(|w| w.started().set());
+
+                let next_buffer = 1 - current_buffer;
+                r.sample
+                    .ptr
+                    .write(|w| unsafe { w.sampleptr().bits(bufs[next_buffer].as_mut_ptr() as u32) });
+            }
+
+            if r.events_stopped.read().bits() != 0 {
+                return Poll::Ready(());
+            }
+
+            Poll::Pending
+        })
+        .await;
+        drop.defuse();
+        Ok(())
+    }
+}
+
+/// PDM microphone driver Config
+pub struct Config {
+    /// Use stero or mono operation
+    pub operation_mode: OperationMode,
+    /// On which edge the left channel should be samples
+    pub edge: Edge,
+    /// Clock frequency
+    pub frequency: Frequency,
+    /// Clock ratio
+    #[cfg(any(
+        feature = "nrf52840",
+        feature = "nrf52833",
+        feature = "_nrf5340-app",
+        feature = "_nrf91",
+    ))]
+    pub ratio: Ratio,
+    /// Gain left in dB
+    pub gain_left: I7F1,
+    /// Gain right in dB
+    pub gain_right: I7F1,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Self {
+            operation_mode: OperationMode::Mono,
+            edge: Edge::LeftFalling,
+            frequency: Frequency::DEFAULT,
+            #[cfg(any(
+                feature = "nrf52840",
+                feature = "nrf52833",
+                feature = "_nrf5340-app",
+                feature = "_nrf91",
+            ))]
+            ratio: Ratio::RATIO80,
+            gain_left: I7F1::ZERO,
+            gain_right: I7F1::ZERO,
+        }
+    }
+}
+
+/// PDM operation mode
+#[derive(PartialEq)]
+pub enum OperationMode {
+    /// Mono (1 channel)
+    Mono,
+    /// Stereo (2 channels)
+    Stereo,
+}
+
+impl From<OperationMode> for OPERATION_A {
+    fn from(mode: OperationMode) -> Self {
+        match mode {
+            OperationMode::Mono => OPERATION_A::MONO,
+            OperationMode::Stereo => OPERATION_A::STEREO,
+        }
+    }
+}
+
+/// PDM edge polarity
+#[derive(PartialEq)]
+pub enum Edge {
+    /// Left edge is rising
+    LeftRising,
+    /// Left edge is falling
+    LeftFalling,
+}
+
+impl From<Edge> for EDGE_A {
+    fn from(edge: Edge) -> Self {
+        match edge {
+            Edge::LeftRising => EDGE_A::LEFT_RISING,
+            Edge::LeftFalling => EDGE_A::LEFT_FALLING,
+        }
+    }
+}
+
+impl<'d, T: Instance> Drop for Pdm<'d, T> {
+    fn drop(&mut self) {
+        let r = T::regs();
+
+        r.tasks_stop.write(|w| unsafe { w.bits(1) });
+
+        r.enable.write(|w| w.enable().disabled());
+
+        r.psel.din.reset();
+        r.psel.clk.reset();
+    }
+}
+
+/// Peripheral static state
+pub(crate) struct State {
+    waker: AtomicWaker,
+}
+
+impl State {
+    pub(crate) const fn new() -> Self {
+        Self {
+            waker: AtomicWaker::new(),
+        }
+    }
+}
+
+pub(crate) trait SealedInstance {
+    fn regs() -> &'static crate::pac::pdm::RegisterBlock;
+    fn state() -> &'static State;
+}
+
+/// PDM peripheral instance
+#[allow(private_bounds)]
+pub trait Instance: Peripheral<P = Self> + SealedInstance + 'static + Send {
+    /// Interrupt for this peripheral
+    type Interrupt: interrupt::typelevel::Interrupt;
+}
+
+macro_rules! impl_pdm {
+    ($type:ident, $pac_type:ident, $irq:ident) => {
+        impl crate::pdm::SealedInstance for peripherals::$type {
+            fn regs() -> &'static crate::pac::pdm::RegisterBlock {
+                unsafe { &*pac::$pac_type::ptr() }
+            }
+            fn state() -> &'static crate::pdm::State {
+                static STATE: crate::pdm::State = crate::pdm::State::new();
+                &STATE
+            }
+        }
+        impl crate::pdm::Instance for peripherals::$type {
+            type Interrupt = crate::interrupt::typelevel::$irq;
+        }
+    };
+}