Draft: Initial support for I2S with a working example.

Co-authored-by: @brainstorm <brainstorm@nopcode.org>

examples/nrf/Cargo.toml

@@ -14,7 +14,7 @@ embassy-futures = { version = "0.1.0", path = "../../embassy-futures" }
 embassy-sync = { version = "0.1.0", path = "../../embassy-sync", features = ["defmt"] }
 embassy-executor = { version = "0.1.0", path = "../../embassy-executor", features = ["defmt", "integrated-timers"] }
 embassy-time = { version = "0.1.0", path = "../../embassy-time", features = ["defmt", "defmt-timestamp-uptime"] }
-embassy-nrf = { version = "0.1.0", path = "../../embassy-nrf", features = ["defmt", "nrf52840", "time-driver-rtc1", "gpiote", "unstable-pac"] }
+embassy-nrf = { version = "0.1.0", path = "../../embassy-nrf", features = ["defmt", "nrf52840", "time-driver-rtc1", "gpiote", "i2s", "unstable-pac"] }
 embassy-net = { version = "0.1.0", path = "../../embassy-net", features = ["defmt", "tcp", "dhcpv4", "medium-ethernet", "pool-16"], optional = true }
 embassy-usb = { version = "0.1.0", path = "../../embassy-usb", features = ["defmt"], optional = true }
 embedded-io = "0.3.1"

examples/nrf/src/bin/i2s.rs

@@ -0,0 +1,48 @@
+// Example inspired by RTIC's I2S demo: https://github.com/nrf-rs/nrf-hal/blob/master/examples/i2s-controller-demo/src/main.rs
+
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_nrf::{i2s};
+use {defmt_rtt as _, panic_probe as _};
+
+#[repr(align(4))]
+pub struct Aligned<T: ?Sized>(T);
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_nrf::init(Default::default());
+    let config = i2s::Config::default();
+
+    let mut i2s = i2s::I2s::new(p.I2S, p.P0_28, p.P0_29, p.P0_31, p.P0_11, p.P0_30, config);
+    
+    let mut signal_buf: Aligned<[i16; 32]> = Aligned([0i16; 32]);
+    let len = signal_buf.0.len() / 2;
+    for x in 0..len {
+        signal_buf.0[2 * x] = triangle_wave(x as i32, len, 2048, 0, 1) as i16;
+        signal_buf.0[2 * x + 1] = triangle_wave(x as i32, len, 2048, 0, 1) as i16;
+    }
+
+    let ptr = &signal_buf.0 as *const i16 as *const u8;
+    let len = signal_buf.0.len() * core::mem::size_of::<i16>();
+
+    i2s.start();
+    i2s.set_tx_enabled(true);
+    
+    loop {
+        i2s.tx(ptr, len).await;
+    }
+}
+
+fn triangle_wave(x: i32, length: usize, amplitude: i32, phase: i32, periods: i32) -> i32 {
+    let length = length as i32;
+    amplitude
+        - ((2 * periods * (x + phase + length / (4 * periods)) * amplitude / length)
+            % (2 * amplitude)
+            - amplitude)
+            .abs()
+        - amplitude / 2
+}