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Improve rp2040 i2c slave

Browse source 
This commit takes the fixes and error reporting improvements from
jcdickinson's work and applies them without overlaying a software state
machine on top of the hardware state machine.

Also allows configuration of response to 'general call' writes.
This commit is contained in:
Caleb Jamison 2024-02-15 17:43:20 -05:00
parent 5220453d85
commit bd0b450ca4
2 changed files with 147 additions and 89 deletions
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130
embassy-rp/src/i2c_slave.rs
View file

@ -4,6 +4,7 @@ use core::marker::PhantomData;
use core::task::Poll;
use embassy_hal_internal::into_ref;
use embassy_time::{block_for, Duration};
use pac::i2c;
use crate::i2c::{
@ -21,6 +22,16 @@ pub enum Error {
Abort(AbortReason),
/// User passed in a response buffer that was 0 length
InvalidResponseBufferLength,
/// The response buffer length was too short to contain the message
///
/// The length parameter will always be the length of the buffer, and is
/// provided as a convenience for matching alongside `Command::Write`.
PartialWrite(usize),
/// The response buffer length was too short to contain the message
///
/// The length parameter will always be the length of the buffer, and is
/// provided as a convenience for matching alongside `Command::GeneralCall`.
PartialGeneralCall(usize),
}
/// Received command
@ -56,17 +67,23 @@ pub enum ReadStatus {
pub struct Config {
/// Target Address
pub addr: u16,
/// Control if the peripheral should ack to and report general calls.
pub general_call: bool,
}
impl Default for Config {
fn default() -> Self {
Self { addr: 0x55 }
Self {
addr: 0x55,
general_call: true,
}
}
}
/// I2CSlave driver.
pub struct I2cSlave<'d, T: Instance> {
phantom: PhantomData<&'d mut T>,
pending_byte: Option<u8>,
}
impl<'d, T: Instance> I2cSlave<'d, T> {
@ -96,7 +113,19 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
w.set_master_mode(false);
w.set_ic_slave_disable(false);
w.set_tx_empty_ctrl(true);
w.set_rx_fifo_full_hld_ctrl(true);
// This typically makes no sense for a slave, but it is used to
// tune spike suppression, according to the datasheet.
w.set_speed(pac::i2c::vals::Speed::FAST);
// Generate stop interrupts for general calls
// This also causes stop interrupts for other devices on the bus but those will not be
// propagated up to the application.
w.set_stop_det_ifaddressed(!config.general_call);
});
p.ic_ack_general_call()
.write(|w| w.set_ack_gen_call(config.general_call));
// Set FIFO watermarks to 1 to make things simpler. This is encoded
// by a register value of 0. Rx watermark should never change, but Tx watermark will be
@ -119,7 +148,10 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
T::Interrupt::unpend();
unsafe { T::Interrupt::enable() };
Self { phantom: PhantomData }
Self {
phantom: PhantomData,
pending_byte: None,
}
}
/// Calls `f` to check if we are ready or not.
@ -133,8 +165,6 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
future::poll_fn(|cx| {
let r = f(self);
trace!("intr p: {:013b}", T::regs().ic_raw_intr_stat().read().0);
if r.is_pending() {
T::waker().register(cx.waker());
g(self);
@ -146,14 +176,36 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
}
#[inline(always)]
fn drain_fifo(&mut self, buffer: &mut [u8], offset: usize) -> usize {
fn drain_fifo(&mut self, buffer: &mut [u8], offset: &mut usize) {
let p = T::regs();
let len = p.ic_rxflr().read().rxflr() as usize;
let end = offset + len;
for i in offset..end {
buffer[i] = p.ic_data_cmd().read().dat();
for b in &mut buffer[*offset..] {
if let Some(pending) = self.pending_byte.take() {
*b = pending;
*offset += 1;
continue;
}
let status = p.ic_status().read();
if !status.rfne() {
break;
}
let dat = p.ic_data_cmd().read();
if *offset != 0 && dat.first_data_byte() {
// The RP2040 state machine will keep placing bytes into the
// FIFO, even if they are part of a subsequent write transaction.
//
// Unfortunately merely reading ic_data_cmd will consume that
// byte, the first byte of the next transaction, so we need
// to store it elsewhere
self.pending_byte = Some(dat.dat());
break;
}
*b = dat.dat();
*offset += 1;
}
end
}
#[inline(always)]
@ -165,32 +217,46 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
}
/// Wait asynchronously for commands from an I2C master.
/// `buffer` is provided in case master does a 'write' and is unused for 'read'.
/// `buffer` is provided in case master does a 'write', 'write read', or 'general call' and is unused for 'read'.
pub async fn listen(&mut self, buffer: &mut [u8]) -> Result<Command, Error> {
let p = T::regs();
p.ic_clr_intr().read();
// set rx fifo watermark to 1 byte
p.ic_rx_tl().write(|w| w.set_rx_tl(0));
let mut len = 0;
let ret = self
.wait_on(
self.wait_on(
|me| {
let stat = p.ic_raw_intr_stat().read();
if p.ic_rxflr().read().rxflr() > 0 {
len = me.drain_fifo(buffer, len);
// we're recieving data, set rx fifo watermark to 12 bytes to reduce interrupt noise
me.drain_fifo(buffer, &mut len);
// we're recieving data, set rx fifo watermark to 12 bytes (3/4 full) to reduce interrupt noise
p.ic_rx_tl().write(|w| w.set_rx_tl(11));
}
if buffer.len() == len {
if stat.gen_call() {
return Poll::Ready(Err(Error::PartialGeneralCall(buffer.len())));
} else {
return Poll::Ready(Err(Error::PartialWrite(buffer.len())));
}
}
if stat.restart_det() && stat.rd_req() {
p.ic_clr_restart_det().read();
Poll::Ready(Ok(Command::WriteRead(len)))
} else if stat.gen_call() && stat.stop_det() && len > 0 {
p.ic_clr_gen_call().read();
p.ic_clr_stop_det().read();
Poll::Ready(Ok(Command::GeneralCall(len)))
} else if stat.stop_det() {
} else if stat.stop_det() && len > 0 {
p.ic_clr_stop_det().read();
Poll::Ready(Ok(Command::Write(len)))
} else if stat.rd_req() {
p.ic_clr_stop_det().read();
p.ic_clr_restart_det().read();
p.ic_clr_gen_call().read();
Poll::Ready(Ok(Command::Read))
} else {
Poll::Pending
@ -206,11 +272,7 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
});
},
)
.await;
p.ic_clr_intr().read();
ret
.await
}
/// Respond to an I2C master READ command, asynchronously.
@ -223,11 +285,11 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
let mut chunks = buffer.chunks(FIFO_SIZE as usize);
let ret = self
.wait_on(
self.wait_on(
|me| {
if let Err(abort_reason) = me.read_and_clear_abort_reason() {
if let Error::Abort(AbortReason::TxNotEmpty(bytes)) = abort_reason {
p.ic_clr_intr().read();
return Poll::Ready(Ok(ReadStatus::LeftoverBytes(bytes)));
} else {
return Poll::Ready(Err(abort_reason));
@ -237,13 +299,17 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
if let Some(chunk) = chunks.next() {
me.write_to_fifo(chunk);
p.ic_clr_rd_req().read();
Poll::Pending
} else {
let stat = p.ic_raw_intr_stat().read();
if stat.rx_done() && stat.stop_det() {
p.ic_clr_rx_done().read();
p.ic_clr_stop_det().read();
Poll::Ready(Ok(ReadStatus::Done))
} else if stat.rd_req() {
} else if stat.rd_req() && stat.tx_empty() {
Poll::Ready(Ok(ReadStatus::NeedMoreBytes))
} else {
Poll::Pending
@ -259,11 +325,7 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
})
},
)
.await;
p.ic_clr_intr().read();
ret
.await
}
/// Respond to reads with the fill byte until the controller stops asking
@ -294,10 +356,6 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
let p = T::regs();
let mut abort_reason = p.ic_tx_abrt_source().read();
// Mask off fifo flush count
let tx_flush_cnt = abort_reason.tx_flush_cnt();
abort_reason.set_tx_flush_cnt(0);
// Mask off master_dis
abort_reason.set_abrt_master_dis(false);
@ -314,8 +372,8 @@ impl<'d, T: Instance> I2cSlave<'d, T> {
AbortReason::NoAcknowledge
} else if abort_reason.arb_lost() {
AbortReason::ArbitrationLoss
} else if abort_reason.abrt_slvflush_txfifo() {
AbortReason::TxNotEmpty(tx_flush_cnt)
} else if abort_reason.tx_flush_cnt() > 0 {
AbortReason::TxNotEmpty(abort_reason.tx_flush_cnt())
} else {
AbortReason::Other(abort_reason.0)
};

2
examples/rp/src/bin/i2c_slave.rs
View file

@ -110,7 +110,7 @@ async fn main(spawner: Spawner) {
let c_sda = p.PIN_1;
let c_scl = p.PIN_0;
let mut config = i2c::Config::default();
config.frequency = 5_000;
config.frequency = 1_000_000;
let controller = i2c::I2c::new_async(p.I2C0, c_sda, c_scl, Irqs, config);
unwrap!(spawner.spawn(controller_task(controller)));