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RP2040/235x: Add I2C bus lockup detection and async recovery implementation. #4908

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RP2040/235x: Add I2C bus lockup detection and async recovery implementation. #4908

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1 change: 1 addition & 0 deletions embassy-rp/CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
- Add reset_to_usb_boot for rp235x ([#4705](https://github.com/embassy-rs/embassy/pull/4705))
- Add fix #4822 in PIO onewire. Change to disable the state machine before setting y register ([#4824](https://github.com/embassy-rs/embassy/pull/4824))
- Add PIO::Ws2812 color order support
- Add I2C bus lockup detection and recovery (recovery is async-only)

## 0.8.0 - 2025-08-26

Expand Down
133 changes: 118 additions & 15 deletions embassy-rp/src/i2c.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,11 +5,13 @@ use core::future;
use core::marker::PhantomData;
use core::task::Poll;

use embassy_hal_internal::drop::OnDrop;
use embassy_hal_internal::{Peri, PeripheralType};
use embassy_sync::waitqueue::AtomicWaker;
use embassy_time::Timer;
use pac::i2c;

use crate::gpio::AnyPin;
use crate::gpio::{AnyPin, Pin, SealedPin};
use crate::interrupt::typelevel::{Binding, Interrupt};
use crate::{interrupt, pac, peripherals};

Expand Down Expand Up @@ -41,6 +43,10 @@ pub enum Error {
InvalidWriteBufferLength,
/// Target i2c address is out of range
AddressOutOfRange(u16),
/// SDA is being held low
SDAHeldLow,
/// SCL is being held low
SCLHeldLow,
/// Target i2c address is reserved
#[deprecated = "embassy_rp no longer prevents accesses to reserved addresses."]
AddressReserved(u16),
Expand Down Expand Up @@ -88,9 +94,10 @@ impl Default for Config {
pub const FIFO_SIZE: u8 = 16;

/// I2C driver.
#[derive(Debug)]
pub struct I2c<'d, T: Instance, M: Mode> {
phantom: PhantomData<(&'d mut T, M)>,
sda: Peri<'d, AnyPin>,
scl: Peri<'d, AnyPin>,
}

impl<'d, T: Instance> I2c<'d, T, Blocking> {
Expand Down Expand Up @@ -159,6 +166,15 @@ impl<'d, T: Instance> I2c<'d, T, Async> {

let mut abort_reason = Ok(());

// Cancel-safety
let on_drop = OnDrop::new(|| {
// Abort
p.ic_enable().write(|w| {
w.set_abort(true);
w.set_enable(true);
});
});

while remaining > 0 {
// Waggle SCK - basically the same as write
let tx_fifo_space = Self::tx_fifo_capacity();
Expand Down Expand Up @@ -226,7 +242,9 @@ impl<'d, T: Instance> I2c<'d, T, Async> {
};
}

self.wait_stop_det(abort_reason, send_stop).await
let res = self.wait_stop_det(abort_reason, send_stop).await;
on_drop.defuse();
res
}

async fn write_async_internal(
Expand All @@ -238,6 +256,15 @@ impl<'d, T: Instance> I2c<'d, T, Async> {

let mut bytes = bytes.into_iter().peekable();

// Cancel-safety
let on_drop = OnDrop::new(|| {
// Abort
p.ic_enable().write(|w| {
w.set_abort(true);
w.set_enable(true);
});
});

let res = 'xmit: loop {
let tx_fifo_space = Self::tx_fifo_capacity();

Expand Down Expand Up @@ -285,7 +312,9 @@ impl<'d, T: Instance> I2c<'d, T, Async> {
}
};

self.wait_stop_det(res, send_stop).await
let res = self.wait_stop_det(res, send_stop).await;
on_drop.defuse();
res
}

/// Helper to wait for a stop bit, for both tx and rx. If we had an abort,
Expand Down Expand Up @@ -329,7 +358,7 @@ impl<'d, T: Instance> I2c<'d, T, Async> {

/// Read from address into buffer asynchronously.
pub async fn read_async(&mut self, addr: impl Into<u16>, buffer: &mut [u8]) -> Result<(), Error> {
Self::setup(addr.into())?;
self.setup_with_recovery(addr.into()).await?;
self.read_async_internal(buffer, true, true).await
}

Expand All @@ -339,7 +368,7 @@ impl<'d, T: Instance> I2c<'d, T, Async> {
addr: impl Into<u16>,
bytes: impl IntoIterator<Item = u8>,
) -> Result<(), Error> {
Self::setup(addr.into())?;
self.setup_with_recovery(addr.into()).await?;
self.write_async_internal(bytes, true).await
}

Expand All @@ -350,7 +379,7 @@ impl<'d, T: Instance> I2c<'d, T, Async> {
bytes: impl IntoIterator<Item = u8>,
buffer: &mut [u8],
) -> Result<(), Error> {
Self::setup(addr.into())?;
self.setup_with_recovery(addr.into()).await?;
self.write_async_internal(bytes, false).await?;
self.read_async_internal(buffer, true, true).await
}
Expand Down Expand Up @@ -399,7 +428,11 @@ impl<'d, T: Instance + 'd, M: Mode> I2c<'d, T, M> {
set_up_i2c_pin(&scl, config.scl_pullup);
set_up_i2c_pin(&sda, config.sda_pullup);

let mut me = Self { phantom: PhantomData };
let mut me = Self {
phantom: PhantomData,
scl: scl.into(),
sda: sda.into(),
};

if let Err(e) = me.set_config_inner(&config) {
panic!("Error configuring i2c: {:?}", e);
Expand Down Expand Up @@ -473,18 +506,86 @@ impl<'d, T: Instance + 'd, M: Mode> I2c<'d, T, M> {
Ok(())
}

fn setup(addr: u16) -> Result<(), Error> {
fn is_scl_low(&self) -> bool {
self.scl.sio_in().read() & (1 << (self.scl.pin() % 32)) == 0
}

fn is_sda_low(&self) -> bool {
self.sda.sio_in().read() & (1 << (self.sda.pin() % 32)) == 0
}

fn setup(&self, addr: u16) -> Result<(), Error> {
if addr >= 0x80 {
return Err(Error::AddressOutOfRange(addr));
}

let p = T::regs();
p.ic_enable().write(|w| w.set_enable(false));

if self.is_sda_low() {
return Err(Error::SDAHeldLow);
}
if self.is_scl_low() {
return Err(Error::SCLHeldLow);
}

p.ic_tar().write(|w| w.set_ic_tar(addr));
p.ic_enable().write(|w| w.set_enable(true));
Ok(())
}

async fn setup_with_recovery(&mut self, addr: u16) -> Result<(), Error> {
let setup_result = self.setup(addr);
if setup_result == Err(Error::SDAHeldLow) {
#[cfg(feature = "defmt")]
defmt::warn!("SDA held low, attempting recovery");
// Cancel safety
let on_drop = OnDrop::new(|| {
// Set back to i2c mode
self.scl.gpio().ctrl().write(|w| w.set_funcsel(3));
self.sda.gpio().ctrl().write(|w| w.set_funcsel(3));
});

let scl_pin_bit = 1 << (self.scl.pin() % 32);
let sda_pin_bit = 1 << (self.sda.pin() % 32);
// Set low and flip between input for high and output for low
self.scl.sio_out().value_clr().write_value(scl_pin_bit);
self.sda.sio_out().value_clr().write_value(sda_pin_bit);
self.scl.sio_oe().value_clr().write_value(scl_pin_bit); // Input => High
self.sda.sio_oe().value_clr().write_value(sda_pin_bit); // Input => High
// Switch to sio mode
self.scl.gpio().ctrl().write(|w| w.set_funcsel(0x05));
self.sda.gpio().ctrl().write(|w| w.set_funcsel(0x05));
// Attempt automatic recovery
for _ in 0..9 {
self.scl.sio_oe().value_set().write_value(scl_pin_bit); // Low
Timer::after_micros(5).await;
self.scl.sio_oe().value_clr().write_value(scl_pin_bit); // High
Timer::after_micros(5).await;
if !self.is_sda_low() {
// Recovery successful
#[cfg(feature = "defmt")]
defmt::warn!("SDA recovered");
break;
}
}
if !self.is_sda_low() {
// Send a stop
self.sda.sio_oe().value_set().write_value(sda_pin_bit); // Low
Timer::after_micros(5).await;
self.sda.sio_oe().value_clr().write_value(sda_pin_bit); // High
Timer::after_micros(5).await;
}
// Reset gpio config
drop(on_drop);

self.read_and_clear_abort_reason().ok();
self.setup(addr)
} else {
setup_result
}
}

#[inline]
fn tx_fifo_full() -> bool {
Self::tx_fifo_capacity() == 0
Expand Down Expand Up @@ -606,20 +707,20 @@ impl<'d, T: Instance + 'd, M: Mode> I2c<'d, T, M> {

/// Read from address into buffer blocking caller until done.
pub fn blocking_read(&mut self, address: impl Into<u16>, read: &mut [u8]) -> Result<(), Error> {
Self::setup(address.into())?;
self.setup(address.into())?;
self.read_blocking_internal(read, true, true)
// Automatic Stop
}

/// Write to address from buffer blocking caller until done.
pub fn blocking_write(&mut self, address: impl Into<u16>, write: &[u8]) -> Result<(), Error> {
Self::setup(address.into())?;
self.setup(address.into())?;
self.write_blocking_internal(write, true)
}

/// Write to address from bytes and read from address into buffer blocking caller until done.
pub fn blocking_write_read(&mut self, address: impl Into<u16>, write: &[u8], read: &mut [u8]) -> Result<(), Error> {
Self::setup(address.into())?;
self.setup(address.into())?;
self.write_blocking_internal(write, false)?;
self.read_blocking_internal(read, true, true)
// Automatic Stop
Expand Down Expand Up @@ -658,7 +759,7 @@ impl<'d, T: Instance, M: Mode> embedded_hal_02::blocking::i2c::Transactional for
address: u8,
operations: &mut [embedded_hal_02::blocking::i2c::Operation<'_>],
) -> Result<(), Self::Error> {
Self::setup(address.into())?;
self.setup(address.into())?;
for i in 0..operations.len() {
let last = i == operations.len() - 1;
match &mut operations[i] {
Expand All @@ -684,6 +785,8 @@ impl embedded_hal_1::i2c::Error for Error {
Self::InvalidReadBufferLength => embedded_hal_1::i2c::ErrorKind::Other,
Self::InvalidWriteBufferLength => embedded_hal_1::i2c::ErrorKind::Other,
Self::AddressOutOfRange(_) => embedded_hal_1::i2c::ErrorKind::Other,
Self::SDAHeldLow => embedded_hal_1::i2c::ErrorKind::Bus,
Self::SCLHeldLow => embedded_hal_1::i2c::ErrorKind::Bus,
#[allow(deprecated)]
Self::AddressReserved(_) => embedded_hal_1::i2c::ErrorKind::Other,
}
Expand Down Expand Up @@ -712,7 +815,7 @@ impl<'d, T: Instance, M: Mode> embedded_hal_1::i2c::I2c for I2c<'d, T, M> {
address: u8,
operations: &mut [embedded_hal_1::i2c::Operation<'_>],
) -> Result<(), Self::Error> {
Self::setup(address.into())?;
self.setup(address.into())?;
for i in 0..operations.len() {
let last = i == operations.len() - 1;
match &mut operations[i] {
Expand Down Expand Up @@ -751,7 +854,7 @@ where
let addr: u16 = address.into();

if !operations.is_empty() {
Self::setup(addr)?;
self.setup_with_recovery(addr).await?;
}
let mut iterator = operations.iter_mut();

Expand Down