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RP2040/235x: Fixed significant issue with i2c slave respond_to_read #4903

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RP2040/235x: Fixed significant issue with i2c slave respond_to_read #4903

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8ef4129
Fixed issue with rp i2c slave respond_to_read
computer-whisperer Nov 17, 2025
b7077f9
Rustfmt and changelog bump.
computer-whisperer Nov 17, 2025
f61f243
Rustfmt
computer-whisperer Nov 17, 2025
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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
- Fix i2c_slave respond_to_read for buffers larger than one chunk

## 0.8.0 - 2025-08-26

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9 changes: 5 additions & 4 deletions embassy-rp/src/i2c_slave.rs
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Expand Up @@ -301,7 +301,7 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
return Err(Error::InvalidResponseBufferLength);
}

let mut chunks = buffer.chunks(FIFO_SIZE as usize);
let mut bytes_written = 0;

self.wait_on(
|me| {
Expand All @@ -319,10 +319,11 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
}
}

if let Some(chunk) = chunks.next() {
for byte in chunk {
if bytes_written < buffer.len() {
for _ in 0..((FIFO_SIZE - p.ic_txflr().read().txflr()) as usize).min(buffer.len() - bytes_written) {
p.ic_clr_rd_req().read();
p.ic_data_cmd().write(|w| w.set_dat(*byte));
p.ic_data_cmd().write(|w| w.set_dat(buffer[bytes_written]));
bytes_written += 1;
}

Poll::Pending
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