From 241129c569023dc71d0025cdc41bcfe40418e7b8 Mon Sep 17 00:00:00 2001
From: Thor McAvenia <mcaveniathor@gmail.com>
Date: Fri, 16 May 2025 00:09:10 -0700
Subject: Add PioI2sIn, PioI2sInProgram, and example binary

---
 examples/rp235x/src/bin/pio_i2s_rx.rs | 81 +++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 examples/rp235x/src/bin/pio_i2s_rx.rs

(limited to 'examples')

diff --git a/examples/rp235x/src/bin/pio_i2s_rx.rs b/examples/rp235x/src/bin/pio_i2s_rx.rs
new file mode 100644
index 000000000..c3f505b13
--- /dev/null
+++ b/examples/rp235x/src/bin/pio_i2s_rx.rs
@@ -0,0 +1,81 @@
+//! This example shows receiving audio from a connected I2S microphone (or other audio source)
+//! using the PIO module of the RP235x.
+//!
+//!
+//! Connect the i2s microphone as follows:
+//!   bclk : GPIO 18
+//!   lrc  : GPIO 19
+//!   din  : GPIO 20
+//! Then hold down the boot select button to begin receiving audio. Received I2S words will be written to
+//! buffers for the left and right channels for use in your application, whether that's storage or
+//! further processing
+//!
+//!  Note the const USE_ONBOARD_PULLDOWN is by default set to false, meaning an external
+//!  pull-down resistor is being used on the data pin if required by the mic being used.
+
+#![no_std]
+#![no_main]
+use core::mem;
+
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_rp::bind_interrupts;
+use embassy_rp::peripherals::PIO0;
+use embassy_rp::pio::{InterruptHandler, Pio};
+use embassy_rp::pio_programs::i2s::{PioI2sIn, PioI2sInProgram};
+use static_cell::StaticCell;
+use {defmt_rtt as _, panic_probe as _};
+
+bind_interrupts!(struct Irqs {
+    PIO0_IRQ_0 => InterruptHandler<PIO0>;
+});
+
+const SAMPLE_RATE: u32 = 48_000;
+const BIT_DEPTH: u32 = 16;
+const CHANNELS: u32 = 2;
+const USE_ONBOARD_PULLDOWN: bool = false; // whether or not to use the onboard pull-down resistor,
+                                          // which has documented issues on many RP235x boards
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_rp::init(Default::default());
+
+    // Setup pio state machine for i2s input
+    let Pio { mut common, sm0, .. } = Pio::new(p.PIO0, Irqs);
+
+    let bit_clock_pin = p.PIN_18;
+    let left_right_clock_pin = p.PIN_19;
+    let data_pin = p.PIN_20;
+
+    let program = PioI2sInProgram::new(&mut common);
+    let mut i2s = PioI2sIn::new(
+        &mut common,
+        sm0,
+        p.DMA_CH0,
+        USE_ONBOARD_PULLDOWN,
+        data_pin,
+        bit_clock_pin,
+        left_right_clock_pin,
+        SAMPLE_RATE,
+        BIT_DEPTH,
+        CHANNELS,
+        &program,
+    );
+
+    // create two audio buffers (back and front) which will take turns being
+    // filled with new audio data from the PIO fifo using DMA
+    const BUFFER_SIZE: usize = 960;
+    static DMA_BUFFER: StaticCell<[u32; BUFFER_SIZE * 2]> = StaticCell::new();
+    let dma_buffer = DMA_BUFFER.init_with(|| [0u32; BUFFER_SIZE * 2]);
+    let (mut back_buffer, mut front_buffer) = dma_buffer.split_at_mut(BUFFER_SIZE);
+
+    loop {
+        // trigger transfer of front buffer data to the pio fifo
+        // but don't await the returned future, yet
+        let dma_future = i2s.read(front_buffer);
+        // now await the dma future. once the dma finishes, the next buffer needs to be queued
+        // within DMA_DEPTH / SAMPLE_RATE = 8 / 48000 seconds = 166us
+        dma_future.await;
+        info!("Received I2S data word: {:?}", &front_buffer);
+        mem::swap(&mut back_buffer, &mut front_buffer);
+    }
+}
-- 
cgit