Initial PDM driver

embassy-nrf/src/chips/nrf52810.rs

@@ -128,6 +128,9 @@ embassy_hal_common::peripherals! {
 
     // QDEC
     QDEC,
+
+    // PDM
+    PDM,
 }
 
 impl_uarte!(UARTE0, UARTE0, UARTE0_UART0);

embassy-nrf/src/chips/nrf52811.rs

@@ -128,6 +128,9 @@ embassy_hal_common::peripherals! {
 
     // QDEC
     QDEC,
+
+    // PDM
+    PDM,
 }
 
 impl_uarte!(UARTE0, UARTE0, UARTE0_UART0);

embassy-nrf/src/chips/nrf52832.rs

@@ -138,6 +138,9 @@ embassy_hal_common::peripherals! {
 
     // QDEC
     QDEC,
+
+    // PDM
+    PDM,
 }
 
 impl_uarte!(UARTE0, UARTE0, UARTE0_UART0);

embassy-nrf/src/chips/nrf52833.rs

@@ -158,6 +158,9 @@ embassy_hal_common::peripherals! {
 
     // QDEC
     QDEC,
+
+    // PDM
+    PDM,
 }
 
 #[cfg(feature = "nightly")]

embassy-nrf/src/chips/nrf52840.rs

@@ -161,6 +161,9 @@ embassy_hal_common::peripherals! {
 
     // TEMP
     TEMP,
+
+    // PDM
+    PDM,
 }
 
 #[cfg(feature = "nightly")]

embassy-nrf/src/lib.rs

@@ -103,6 +103,14 @@ pub mod uarte;
 pub mod usb;
 #[cfg(not(feature = "_nrf5340"))]
 pub mod wdt;
+#[cfg(any(
+    feature = "nrf52810",
+    feature = "nrf52811",
+    feature = "nrf52832",
+    feature = "nrf52833",
+    feature = "nrf52840",
+))]
+pub mod pdm;
 
 // This mod MUST go last, so that it sees all the `impl_foo!` macros
 #[cfg_attr(feature = "nrf52805", path = "chips/nrf52805.rs")]

embassy-nrf/src/pdm.rs

@@ -0,0 +1,185 @@
+#![macro_use]
+
+use core::sync::atomic::{compiler_fence, Ordering};
+use core::task::Poll;
+
+use embassy_hal_common::{into_ref, PeripheralRef};
+use embassy_util::waitqueue::AtomicWaker;
+use futures::future::poll_fn;
+use pac::{pdm, PDM};
+use pdm::mode::{EDGE_A, OPERATION_A};
+use fixed::types::I7F1;
+
+use crate::interrupt::InterruptExt;
+use crate::gpio::Pin as GpioPin;
+use crate::{interrupt, pac, peripherals, Peripheral};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[non_exhaustive]
+pub enum Error {}
+
+/// One-shot and continuous PDM.
+pub struct Pdm<'d> {
+    _p: PeripheralRef<'d, peripherals::PDM>,
+}
+
+static WAKER: AtomicWaker = AtomicWaker::new();
+
+/// Used to configure the PDM peripheral.
+///
+/// See the `Default` impl for suitable default values.
+#[non_exhaustive]
+pub struct Config {
+    /// Clock
+    /// Clock ratio
+    /// Channels
+    pub channels: Channels,
+    /// Edge to sample on
+    pub left_edge: Edge,
+    /// Gain left in dB
+    pub gain_left: I7F1,
+    /// Gain right in dB
+    pub gain_right: I7F1,
+}
+
+impl Default for Config {
+    /// Default configuration for single channel sampling.
+    fn default() -> Self {
+        Self {
+            channels: Channels::Stereo,
+            left_edge: Edge::FallingEdge,
+            gain_left: I7F1::ZERO,
+            gain_right: I7F1::ZERO,
+        }
+    }
+}
+
+/// 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 {
+    Sampled,
+    Stopped,
+}
+
+impl<'d> Pdm<'d> {
+    pub fn new(
+        pdm: impl Peripheral<P = peripherals::PDM> + 'd,
+        irq: impl Peripheral<P = interrupt::PDM> + 'd,
+        data: impl Peripheral<P = impl GpioPin> + 'd,
+        clock: impl Peripheral<P = impl GpioPin> + 'd,
+        config: Config,
+    ) -> Self {
+        into_ref!(pdm, irq, data, clock);
+
+        let r = unsafe { &*PDM::ptr() };
+
+        let Config { channels, left_edge, gain_left, gain_right } = config;
+
+        // Configure channels
+        r.enable.write(|w| w.enable().enabled());
+        // TODO: Clock control
+        r.mode.write(|w| {
+            w.operation().variant(channels.into());
+            w.edge().variant(left_edge.into());
+            w
+        });
+
+        r.psel.din.write(|w| unsafe { w.bits(data.psel_bits()) });
+        r.psel.clk.write(|w| unsafe { w.bits(clock.psel_bits()) });
+
+        // Disable all events interrupts
+        r.intenclr.write(|w| unsafe { w.bits(0x003F_FFFF) });
+
+        irq.set_handler(Self::on_interrupt);
+        irq.unpend();
+        irq.enable();
+
+        Self { _p: pdm }
+    }
+
+    fn on_interrupt(_ctx: *mut ()) {
+        let r = Self::regs();
+
+        if r.events_end.read().bits() != 0 {
+            r.intenclr.write(|w| w.end().clear());
+            WAKER.wake();
+        }
+
+        if r.events_started.read().bits() != 0 {
+            r.intenclr.write(|w| w.started().clear());
+            WAKER.wake();
+        }
+    }
+
+    fn regs() -> &'static pdm::RegisterBlock {
+        unsafe { &*PDM::ptr() }
+    }
+
+    /// One shot sampling. If the PDM is configured for multiple channels, the samples will be interleaved.
+    pub async fn sample<const N: usize>(&mut self, buf: &mut [i16; N]) {
+        let r = Self::regs();
+
+        // Set up the DMA
+        r.sample.ptr.write(|w| unsafe { w.sampleptr().bits(buf.as_mut_ptr() as u32) });
+        r.sample.maxcnt.write(|w| unsafe { w.buffsize().bits(N as _) });
+
+        // Reset and enable the end event
+        r.events_end.reset();
+        r.intenset.write(|w| w.end().set());
+
+        // 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| { w.tasks_start().set_bit() });
+
+        // Wait for 'end' event.
+        poll_fn(|cx| {
+            let r = Self::regs();
+
+            WAKER.register(cx.waker());
+
+            if r.events_end.read().bits() != 0 {
+                r.events_end.reset();
+                return Poll::Ready(());
+            }
+
+            Poll::Pending
+        })
+        .await;
+    }
+}
+
+#[derive(Clone, Copy, PartialEq)]
+pub enum Edge {
+    FallingEdge,
+    RisingEdge,
+}
+
+impl From<Edge> for EDGE_A {
+    fn from(edge: Edge) -> Self {
+        match edge {
+            Edge::FallingEdge => EDGE_A::LEFTFALLING,
+            Edge::RisingEdge => EDGE_A::LEFTRISING,
+        }
+    }
+}
+
+#[derive(Clone, Copy, PartialEq)]
+pub enum Channels {
+    Stereo,
+    Mono,
+}
+
+impl From<Channels> for OPERATION_A {
+    fn from(ch: Channels) -> Self {
+        match ch {
+            Channels::Stereo => OPERATION_A::STEREO,
+            Channels::Mono => OPERATION_A::MONO,
+        }
+    }
+}

examples/nrf/Cargo.toml

@@ -27,6 +27,7 @@ cortex-m-rt = "0.7.0"
 panic-probe = { version = "0.3", features = ["print-defmt"] }
 futures = { version = "0.3.17", default-features = false, features = ["async-await"] }
 rand = { version = "0.8.4", default-features = false }
+fixed = "1.10.0"
 embedded-storage = "0.3.0"
 usbd-hid = "0.5.2"
 serde = { version = "1.0.136", default-features = false }

examples/nrf/src/bin/pdm.rs

@@ -0,0 +1,34 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::info;
+use embassy_executor::Spawner;
+use embassy_nrf::interrupt;
+use embassy_nrf::pdm::{Config, Channels, Pdm};
+use embassy_time::{Duration, Timer};
+use fixed::types::I7F1;
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_p: Spawner) {
+    let mut p = embassy_nrf::init(Default::default());
+    let mut config = Config::default();
+    // Pins are correct for the onboard microphone on the Feather nRF52840 Sense.
+    config.channels = Channels::Mono;
+    config.gain_left = I7F1::from_bits(5); // 2.5 dB
+    let mut pdm = Pdm::new(p.PDM, interrupt::take!(PDM), &mut p.P0_00, &mut p.P0_01, config);
+
+    loop {
+        let mut buf = [0; 128];
+        pdm.sample(&mut buf).await;
+        info!(
+            "{} samples, min {=i16}, max {=i16}, mean {=i16}",
+            buf.len(),
+            buf.iter().min().unwrap(),
+            buf.iter().max().unwrap(),
+            (buf.iter().map(|v| i32::from(*v)).sum::<i32>() / buf.len() as i32) as i16,
+        );
+        Timer::after(Duration::from_millis(100)).await;
+    }
+}