Initial PDM driver

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;
+    }
+}