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Merge pull request #4210 from mcaveniathor/pio_i2s_rx
Add PioI2sIn, PioI2sInProgram, and example binary
This commit is contained in:
Dario Nieuwenhuis
GitHub
commit
46bf0c71cc
@ -8,6 +8,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
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<!-- next-header -->
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## Unreleased - ReleaseDate
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- Add PIO SPI
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- Add PIO I2S input
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## 0.8.0 - 2025-08-26
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## 0.7.1 - 2025-08-26
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@ -1,13 +1,101 @@
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//! Pio backed I2s output
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//! Pio backed I2s output and output drivers
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use fixed::traits::ToFixed;
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use crate::dma::{AnyChannel, Channel, Transfer};
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use crate::gpio::Pull;
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use crate::pio::{
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Common, Config, Direction, FifoJoin, Instance, LoadedProgram, PioPin, ShiftConfig, ShiftDirection, StateMachine,
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};
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use crate::Peri;
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/// This struct represents an i2s receiver & controller driver program
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pub struct PioI2sInProgram<'d, PIO: Instance> {
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prg: LoadedProgram<'d, PIO>,
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}
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impl<'d, PIO: Instance> PioI2sInProgram<'d, PIO> {
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/// Load the input program into the given pio
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pub fn new(common: &mut Common<'d, PIO>) -> Self {
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let prg = pio::pio_asm! {
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".side_set 2",
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" set x, 14 side 0b01",
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"left_data:",
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" in pins, 1 side 0b00", // read one left-channel bit from SD
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" jmp x-- left_data side 0b01",
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" in pins, 1 side 0b10", // ws changes 1 clock before MSB
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" set x, 14 side 0b11",
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"right_data:",
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" in pins, 1 side 0b10",
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" jmp x-- right_data side 0b11",
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" in pins, 1 side 0b00" // ws changes 1 clock before ms
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};
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let prg = common.load_program(&prg.program);
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Self { prg }
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}
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}
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/// Pio backed I2s input driver
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pub struct PioI2sIn<'d, P: Instance, const S: usize> {
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dma: Peri<'d, AnyChannel>,
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sm: StateMachine<'d, P, S>,
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}
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impl<'d, P: Instance, const S: usize> PioI2sIn<'d, P, S> {
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/// Configure a state machine to act as both the controller (provider of SCK and WS) and receiver (of SD) for an I2S signal
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pub fn new(
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common: &mut Common<'d, P>,
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mut sm: StateMachine<'d, P, S>,
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dma: Peri<'d, impl Channel>,
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// Whether or not to use the MCU's internal pull-down resistor, as the
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// Pico 2 is known to have problems with the inbuilt pulldowns, many
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// opt to just use an external pull down resistor to meet requirements of common
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// i2s microphones such as the INMP441
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data_pulldown: bool,
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data_pin: Peri<'d, impl PioPin>,
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bit_clock_pin: Peri<'d, impl PioPin>,
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lr_clock_pin: Peri<'d, impl PioPin>,
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sample_rate: u32,
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bit_depth: u32,
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channels: u32,
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program: &PioI2sInProgram<'d, P>,
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) -> Self {
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let mut data_pin = common.make_pio_pin(data_pin);
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if data_pulldown {
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data_pin.set_pull(Pull::Down);
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}
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let bit_clock_pin = common.make_pio_pin(bit_clock_pin);
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let left_right_clock_pin = common.make_pio_pin(lr_clock_pin);
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let cfg = {
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let mut cfg = Config::default();
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cfg.use_program(&program.prg, &[&bit_clock_pin, &left_right_clock_pin]);
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cfg.set_in_pins(&[&data_pin]);
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let clock_frequency = sample_rate * bit_depth * channels;
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cfg.clock_divider = (crate::clocks::clk_sys_freq() as f64 / clock_frequency as f64 / 2.).to_fixed();
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cfg.shift_in = ShiftConfig {
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threshold: 32,
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direction: ShiftDirection::Left,
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auto_fill: true,
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};
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// join fifos to have twice the time to start the next dma transfer
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cfg.fifo_join = FifoJoin::RxOnly; // both control signals are sent via side-setting
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cfg
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};
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sm.set_config(&cfg);
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sm.set_pin_dirs(Direction::In, &[&data_pin]);
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sm.set_pin_dirs(Direction::Out, &[&left_right_clock_pin, &bit_clock_pin]);
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sm.set_enable(true);
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Self { dma: dma.into(), sm }
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}
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/// Return an in-prograss dma transfer future. Awaiting it will guarentee a complete transfer.
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pub fn read<'b>(&'b mut self, buff: &'b mut [u32]) -> Transfer<'b, AnyChannel> {
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self.sm.rx().dma_pull(self.dma.reborrow(), buff, false)
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}
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}
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/// This struct represents an i2s output driver program
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///
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/// The sample bit-depth is set through scratch register `Y`.
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@ -26,12 +114,12 @@ impl<'d, PIO: Instance> PioI2sOutProgram<'d, PIO> {
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"left_data:",
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" out pins, 1 side 0b00",
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" jmp x-- left_data side 0b01",
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" out pins 1 side 0b10",
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" out pins, 1 side 0b10",
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" mov x, y side 0b11",
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"right_data:",
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" out pins 1 side 0b10",
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" out pins, 1 side 0b10",
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" jmp x-- right_data side 0b11",
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" out pins 1 side 0b00",
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" out pins, 1 side 0b00",
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);
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let prg = common.load_program(&prg.program);
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81
examples/rp235x/src/bin/pio_i2s_rx.rs
Normal file
81
examples/rp235x/src/bin/pio_i2s_rx.rs
Normal file
@ -0,0 +1,81 @@
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//! This example shows receiving audio from a connected I2S microphone (or other audio source)
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//! using the PIO module of the RP235x.
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//!
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//!
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//! Connect the i2s microphone as follows:
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//! bclk : GPIO 18
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//! lrc : GPIO 19
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//! din : GPIO 20
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//! Then hold down the boot select button to begin receiving audio. Received I2S words will be written to
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//! buffers for the left and right channels for use in your application, whether that's storage or
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//! further processing
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//!
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//! Note the const USE_ONBOARD_PULLDOWN is by default set to false, meaning an external
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//! pull-down resistor is being used on the data pin if required by the mic being used.
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#![no_std]
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#![no_main]
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use core::mem;
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use defmt::*;
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use embassy_executor::Spawner;
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use embassy_rp::bind_interrupts;
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use embassy_rp::peripherals::PIO0;
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use embassy_rp::pio::{InterruptHandler, Pio};
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use embassy_rp::pio_programs::i2s::{PioI2sIn, PioI2sInProgram};
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use static_cell::StaticCell;
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use {defmt_rtt as _, panic_probe as _};
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bind_interrupts!(struct Irqs {
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PIO0_IRQ_0 => InterruptHandler<PIO0>;
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});
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const SAMPLE_RATE: u32 = 48_000;
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const BIT_DEPTH: u32 = 16;
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const CHANNELS: u32 = 2;
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const USE_ONBOARD_PULLDOWN: bool = false; // whether or not to use the onboard pull-down resistor,
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// which has documented issues on many RP235x boards
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#[embassy_executor::main]
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async fn main(_spawner: Spawner) {
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let p = embassy_rp::init(Default::default());
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// Setup pio state machine for i2s input
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let Pio { mut common, sm0, .. } = Pio::new(p.PIO0, Irqs);
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let bit_clock_pin = p.PIN_18;
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let left_right_clock_pin = p.PIN_19;
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let data_pin = p.PIN_20;
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let program = PioI2sInProgram::new(&mut common);
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let mut i2s = PioI2sIn::new(
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&mut common,
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sm0,
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p.DMA_CH0,
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USE_ONBOARD_PULLDOWN,
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data_pin,
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bit_clock_pin,
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left_right_clock_pin,
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SAMPLE_RATE,
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BIT_DEPTH,
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CHANNELS,
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&program,
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);
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// create two audio buffers (back and front) which will take turns being
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// filled with new audio data from the PIO fifo using DMA
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const BUFFER_SIZE: usize = 960;
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static DMA_BUFFER: StaticCell<[u32; BUFFER_SIZE * 2]> = StaticCell::new();
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let dma_buffer = DMA_BUFFER.init_with(|| [0u32; BUFFER_SIZE * 2]);
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let (mut back_buffer, mut front_buffer) = dma_buffer.split_at_mut(BUFFER_SIZE);
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loop {
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// trigger transfer of front buffer data to the pio fifo
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// but don't await the returned future, yet
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let dma_future = i2s.read(front_buffer);
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// now await the dma future. once the dma finishes, the next buffer needs to be queued
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// within DMA_DEPTH / SAMPLE_RATE = 8 / 48000 seconds = 166us
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dma_future.await;
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info!("Received I2S data word: {:?}", &front_buffer);
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mem::swap(&mut back_buffer, &mut front_buffer);
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}
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}
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