Add support for transactions to Twim in embassy-nrf

embassy-nrf/src/twim.rs

@@ -4,6 +4,7 @@
 
 use core::future::{poll_fn, Future};
 use core::marker::PhantomData;
+use core::mem::MaybeUninit;
 use core::sync::atomic::compiler_fence;
 use core::sync::atomic::Ordering::SeqCst;
 use core::task::Poll;
@@ -13,11 +14,12 @@ use embassy_hal_internal::{into_ref, PeripheralRef};
 use embassy_sync::waitqueue::AtomicWaker;
 #[cfg(feature = "time")]
 use embassy_time::{Duration, Instant};
+use embedded_hal_1::i2c::Operation;
 
 use crate::chip::{EASY_DMA_SIZE, FORCE_COPY_BUFFER_SIZE};
 use crate::gpio::Pin as GpioPin;
 use crate::interrupt::typelevel::Interrupt;
-use crate::util::{slice_in_ram, slice_in_ram_or};
+use crate::util::slice_in_ram;
 use crate::{gpio, interrupt, pac, Peripheral};
 
 /// TWI frequency
@@ -103,6 +105,18 @@ impl<T: Instance> interrupt::typelevel::Handler<T::Interrupt> for InterruptHandl
         let r = T::regs();
         let s = T::state();
 
+        // Workaround for lack of LASTRX_SUSPEND short in some nRF chips
+        // Do this first to minimize latency
+        #[cfg(any(feature = "nrf52832", feature = "_nrf5340", feature = "_nrf9120"))]
+        if r.events_lastrx.read().bits() != 0 {
+            r.tasks_suspend.write(|w| unsafe { w.bits(1) });
+            r.events_lastrx.reset();
+        }
+
+        if r.events_suspended.read().bits() != 0 {
+            s.end_waker.wake();
+            r.intenclr.write(|w| w.suspended().clear());
+        }
         if r.events_stopped.read().bits() != 0 {
             s.end_waker.wake();
             r.intenclr.write(|w| w.stopped().clear());
@@ -182,8 +196,22 @@ impl<'d, T: Instance> Twim<'d, T> {
     }
 
     /// Set TX buffer, checking that it is in RAM and has suitable length.
-    unsafe fn set_tx_buffer(&mut self, buffer: &[u8]) -> Result<(), Error> {
+    unsafe fn set_tx_buffer(
-        slice_in_ram_or(buffer, Error::BufferNotInRAM)?;
+        &mut self,
+        buffer: &[u8],
+        ram_buffer: Option<&mut [MaybeUninit<u8>; FORCE_COPY_BUFFER_SIZE]>,
+    ) -> Result<(), Error> {
+        let buffer = if slice_in_ram(buffer) {
+            buffer
+        } else {
+            let ram_buffer = ram_buffer.ok_or(Error::BufferNotInRAM)?;
+            trace!("Copying TWIM tx buffer into RAM for DMA");
+            let ram_buffer = &mut ram_buffer[..buffer.len()];
+            // Inline implementation of the nightly API MaybeUninit::copy_from_slice(ram_buffer, buffer)
+            let uninit_src: &[MaybeUninit<u8>] = unsafe { core::mem::transmute(buffer) };
+            ram_buffer.copy_from_slice(uninit_src);
+            unsafe { &*(ram_buffer as *const [MaybeUninit<u8>] as *const [u8]) }
+        };
 
         if buffer.len() > EASY_DMA_SIZE {
             return Err(Error::TxBufferTooLong);
@@ -290,7 +318,7 @@ impl<'d, T: Instance> Twim<'d, T> {
     fn blocking_wait(&mut self) {
         let r = T::regs();
         loop {
-            if r.events_stopped.read().bits() != 0 {
+            if r.events_suspended.read().bits() != 0 || r.events_stopped.read().bits() != 0 {
                 r.events_stopped.reset();
                 break;
             }
@@ -307,7 +335,7 @@ impl<'d, T: Instance> Twim<'d, T> {
         let r = T::regs();
         let deadline = Instant::now() + timeout;
         loop {
-            if r.events_stopped.read().bits() != 0 {
+            if r.events_suspended.read().bits() != 0 || r.events_stopped.read().bits() != 0 {
                 r.events_stopped.reset();
                 break;
             }
@@ -331,7 +359,7 @@ impl<'d, T: Instance> Twim<'d, T> {
             let s = T::state();
 
             s.end_waker.register(cx.waker());
-            if r.events_stopped.read().bits() != 0 {
+            if r.events_suspended.read().bits() != 0 || r.events_stopped.read().bits() != 0 {
                 r.events_stopped.reset();
 
                 return Poll::Ready(());
@@ -347,75 +375,13 @@ impl<'d, T: Instance> Twim<'d, T> {
         })
     }
 
-    fn setup_write_from_ram(&mut self, address: u8, buffer: &[u8], inten: bool) -> Result<(), Error> {
+    fn setup_operations(
-        let r = T::regs();
-
-        compiler_fence(SeqCst);
-
-        r.address.write(|w| unsafe { w.address().bits(address) });
-
-        // Set up the DMA write.
-        unsafe { self.set_tx_buffer(buffer)? };
-
-        // Clear events
-        r.events_stopped.reset();
-        r.events_error.reset();
-        r.events_lasttx.reset();
-        self.clear_errorsrc();
-
-        if inten {
-            r.intenset.write(|w| w.stopped().set().error().set());
-        } else {
-            r.intenclr.write(|w| w.stopped().clear().error().clear());
-        }
-
-        // Start write operation.
-        r.shorts.write(|w| w.lasttx_stop().enabled());
-        r.tasks_starttx.write(|w| unsafe { w.bits(1) });
-        if buffer.is_empty() {
-            // With a zero-length buffer, LASTTX doesn't fire (because there's no last byte!), so do the STOP ourselves.
-            r.tasks_stop.write(|w| unsafe { w.bits(1) });
-        }
-        Ok(())
-    }
-
-    fn setup_read(&mut self, address: u8, buffer: &mut [u8], inten: bool) -> Result<(), Error> {
-        let r = T::regs();
-
-        compiler_fence(SeqCst);
-
-        r.address.write(|w| unsafe { w.address().bits(address) });
-
-        // Set up the DMA read.
-        unsafe { self.set_rx_buffer(buffer)? };
-
-        // Clear events
-        r.events_stopped.reset();
-        r.events_error.reset();
-        self.clear_errorsrc();
-
-        if inten {
-            r.intenset.write(|w| w.stopped().set().error().set());
-        } else {
-            r.intenclr.write(|w| w.stopped().clear().error().clear());
-        }
-
-        // Start read operation.
-        r.shorts.write(|w| w.lastrx_stop().enabled());
-        r.tasks_startrx.write(|w| unsafe { w.bits(1) });
-        if buffer.is_empty() {
-            // With a zero-length buffer, LASTRX doesn't fire (because there's no last byte!), so do the STOP ourselves.
-            r.tasks_stop.write(|w| unsafe { w.bits(1) });
-        }
-        Ok(())
-    }
-
-    fn setup_write_read_from_ram(
         &mut self,
         address: u8,
-        wr_buffer: &[u8],
+        operations: &mut [Operation<'_>],
-        rd_buffer: &mut [u8],
+        tx_ram_buffer: Option<&mut [MaybeUninit<u8>; FORCE_COPY_BUFFER_SIZE]>,
         inten: bool,
+        stop: bool,
     ) -> Result<(), Error> {
         let r = T::regs();
 
@@ -423,92 +389,343 @@ impl<'d, T: Instance> Twim<'d, T> {
 
         r.address.write(|w| unsafe { w.address().bits(address) });
 
-        // Set up DMA buffers.
+        let was_suspended = r.events_suspended.read().bits() != 0;
-        unsafe {
+        r.events_suspended.reset();
-            self.set_tx_buffer(wr_buffer)?;
-            self.set_rx_buffer(rd_buffer)?;
-        }
-
-        // Clear events
         r.events_stopped.reset();
         r.events_error.reset();
         self.clear_errorsrc();
 
         if inten {
-            r.intenset.write(|w| w.stopped().set().error().set());
+            r.intenset.write(|w| w.suspended().set().stopped().set().error().set());
         } else {
-            r.intenclr.write(|w| w.stopped().clear().error().clear());
+            r.intenclr
+                .write(|w| w.suspended().clear().stopped().clear().error().clear());
+        }
+        #[cfg(any(feature = "nrf52832", feature = "_nrf5340", feature = "_nrf9120"))]
+        r.intenclr.write(|w| w.lastrx().clear());
+
+        match operations {
+            [Operation::Read(rd_buffer), Operation::Write(wr_buffer), rest @ ..]
+                if !rd_buffer.is_empty() && !wr_buffer.is_empty() =>
+            {
+                let stop = stop && rest.is_empty();
+
+                // Set up DMA buffers.
+                unsafe {
+                    self.set_tx_buffer(wr_buffer, tx_ram_buffer)?;
+                    self.set_rx_buffer(rd_buffer)?;
+                }
+
+                r.shorts.write(|w| {
+                    w.lastrx_starttx().enabled();
+                    if stop {
+                        w.lasttx_stop().enabled();
+                    } else {
+                        w.lasttx_suspend().enabled();
+                    }
+                    w
+                });
+
+                // Start read+write operation.
+                r.tasks_startrx.write(|w| unsafe { w.bits(1) });
+
+                if was_suspended {
+                    r.tasks_resume.write(|w| unsafe { w.bits(1) });
+                }
+            }
+            [Operation::Write(wr_buffer), Operation::Read(rd_buffer), rest @ ..]
+                if !wr_buffer.is_empty() && !rd_buffer.is_empty() =>
+            {
+                let stop = stop && rest.is_empty();
+
+                // Set up DMA buffers.
+                unsafe {
+                    self.set_tx_buffer(wr_buffer, tx_ram_buffer)?;
+                    self.set_rx_buffer(rd_buffer)?;
                 }
 
                 // Start write+read operation.
                 r.shorts.write(|w| {
                     w.lasttx_startrx().enabled();
+                    if stop {
                         w.lastrx_stop().enabled();
+                    } else {
+                        #[cfg(not(any(feature = "nrf52832", feature = "_nrf5340", feature = "_nrf9120")))]
+                        w.lastrx_suspend().enabled();
+                    }
                     w
                 });
+                #[cfg(any(feature = "nrf52832", feature = "_nrf5340", feature = "_nrf9120"))]
+                if !stop {
+                    r.intenset.write(|w| w.lastrx().set());
+                }
+
                 r.tasks_starttx.write(|w| unsafe { w.bits(1) });
-        if wr_buffer.is_empty() && rd_buffer.is_empty() {
+
-            // With a zero-length buffer, LASTRX/LASTTX doesn't fire (because there's no last byte!), so do the STOP ourselves.
+                if was_suspended {
-            // TODO handle when only one of the buffers is zero length
+                    r.tasks_resume.write(|w| unsafe { w.bits(1) });
+                }
+            }
+            [Operation::Read(buffer), rest @ ..] => {
+                let stop = stop && rest.is_empty();
+
+                // Set up DMA buffers.
+                unsafe {
+                    self.set_rx_buffer(buffer)?;
+                }
+
+                // Start read operation.
+                r.shorts.write(|w| {
+                    if stop {
+                        w.lastrx_stop().enabled();
+                    } else {
+                        #[cfg(not(any(feature = "nrf52832", feature = "_nrf5340", feature = "_nrf9120")))]
+                        w.lastrx_suspend().enabled();
+                    }
+                    w
+                });
+                #[cfg(any(feature = "nrf52832", feature = "_nrf5340", feature = "_nrf9120"))]
+                if !stop {
+                    r.intenset.write(|w| w.lastrx().set());
+                }
+
+                r.tasks_startrx.write(|w| unsafe { w.bits(1) });
+
+                if was_suspended {
+                    r.tasks_resume.write(|w| unsafe { w.bits(1) });
+                }
+
+                if buffer.is_empty() {
+                    // With a zero-length buffer, LASTRX doesn't fire (because there's no last byte!), so do the STOP/SUSPEND ourselves.
+                    if stop {
                         r.tasks_stop.write(|w| unsafe { w.bits(1) });
+                    } else {
+                        r.tasks_suspend.write(|w| unsafe { w.bits(1) });
+                    }
+                }
+            }
+            [Operation::Write(buffer), rest @ ..] => {
+                let stop = stop && rest.is_empty();
+
+                // Set up DMA buffers.
+                unsafe {
+                    self.set_tx_buffer(buffer, tx_ram_buffer)?;
+                }
+
+                // Start write operation.
+                r.shorts.write(|w| {
+                    if stop {
+                        w.lasttx_stop().enabled();
+                    } else {
+                        w.lasttx_suspend().enabled();
+                    }
+                    w
+                });
+
+                r.tasks_starttx.write(|w| unsafe { w.bits(1) });
+
+                if was_suspended {
+                    r.tasks_resume.write(|w| unsafe { w.bits(1) });
+                }
+
+                if buffer.is_empty() {
+                    // With a zero-length buffer, LASTTX doesn't fire (because there's no last byte!), so do the STOP/SUSPEND ourselves.
+                    if stop {
+                        r.tasks_stop.write(|w| unsafe { w.bits(1) });
+                    } else {
+                        r.tasks_suspend.write(|w| unsafe { w.bits(1) });
+                    }
+                }
+            }
+            [] => {
+                if stop {
+                    if was_suspended {
+                        r.tasks_resume.write(|w| unsafe { w.bits(1) });
+                    }
+
+                    r.tasks_stop.write(|w| unsafe { w.bits(1) });
+                }
+            }
         }
 
         Ok(())
     }
 
-    fn setup_write_read(
+    fn check_operations(&mut self, operations: &mut [Operation<'_>]) -> Result<usize, Error> {
-        &mut self,
+        compiler_fence(SeqCst);
-        address: u8,
+        self.check_errorsrc()?;
-        wr_buffer: &[u8],
+
-        rd_buffer: &mut [u8],
+        match operations {
-        inten: bool,
+            [Operation::Read(rd_buffer), Operation::Write(wr_buffer), ..]
-    ) -> Result<(), Error> {
+            | [Operation::Write(wr_buffer), Operation::Read(rd_buffer), ..]
-        match self.setup_write_read_from_ram(address, wr_buffer, rd_buffer, inten) {
+                if !rd_buffer.is_empty() && !wr_buffer.is_empty() =>
-            Ok(_) => Ok(()),
+            {
-            Err(Error::BufferNotInRAM) => {
+                self.check_tx(wr_buffer.len())?;
-                trace!("Copying TWIM tx buffer into RAM for DMA");
+                self.check_rx(rd_buffer.len())?;
-                let tx_ram_buf = &mut [0; FORCE_COPY_BUFFER_SIZE][..wr_buffer.len()];
+                Ok(2)
-                tx_ram_buf.copy_from_slice(wr_buffer);
-                self.setup_write_read_from_ram(address, tx_ram_buf, rd_buffer, inten)
             }
-            Err(error) => Err(error),
+            [Operation::Read(buffer), ..] => {
+                self.check_rx(buffer.len())?;
+                Ok(1)
+            }
+            [Operation::Write(buffer), ..] => {
+                self.check_tx(buffer.len())?;
+                Ok(1)
+            }
+            [] => Ok(0),
         }
     }
 
-    fn setup_write(&mut self, address: u8, wr_buffer: &[u8], inten: bool) -> Result<(), Error> {
+    // ===========================================
-        match self.setup_write_from_ram(address, wr_buffer, inten) {
+
-            Ok(_) => Ok(()),
+    /// Execute the provided operations on the I2C bus.
-            Err(Error::BufferNotInRAM) => {
+    ///
-                trace!("Copying TWIM tx buffer into RAM for DMA");
+    /// Each buffer must have a length of at most 255 bytes on the nRF52832
-                let tx_ram_buf = &mut [0; FORCE_COPY_BUFFER_SIZE][..wr_buffer.len()];
+    /// and at most 65535 bytes on the nRF52840.
-                tx_ram_buf.copy_from_slice(wr_buffer);
+    ///
-                self.setup_write_from_ram(address, tx_ram_buf, inten)
+    /// If `stop` is set, the transaction will be terminated with a STOP
+    /// condition and the Twim will be stopped. Otherwise, the bus will be
+    /// left busy via clock stretching and Twim will be suspended.
+    ///
+    /// The nrf52832, nrf5340, and nrf9120 do not have hardware support for
+    /// suspending following a read operation therefore it is emulated by the
+    /// interrupt handler. If the latency of servicing that interrupt is
+    /// longer than a byte worth of clocks on the bus, the SCL clock will
+    /// continue to run for one or more additional bytes. This applies to
+    /// consecutive read operations, certain write-read-write sequences, or
+    /// any sequence of operations ending in a read when `stop == false`.
+    pub fn blocking_transaction(
+        &mut self,
+        address: u8,
+        mut operations: &mut [Operation<'_>],
+        stop: bool,
+    ) -> Result<(), Error> {
+        let mut tx_ram_buffer = [MaybeUninit::uninit(); FORCE_COPY_BUFFER_SIZE];
+        while !operations.is_empty() {
+            self.setup_operations(address, operations, Some(&mut tx_ram_buffer), false, stop)?;
+            self.blocking_wait();
+            let consumed = self.check_operations(operations)?;
+            operations = &mut operations[consumed..];
         }
-            Err(error) => Err(error),
+        Ok(())
     }
+
+    /// Same as [`blocking_transaction`](Twim::blocking_transaction) but will fail instead of copying data into RAM. Consult the module level documentation to learn more.
+    pub fn blocking_transaction_from_ram(
+        &mut self,
+        address: u8,
+        mut operations: &mut [Operation<'_>],
+        stop: bool,
+    ) -> Result<(), Error> {
+        while !operations.is_empty() {
+            self.setup_operations(address, operations, None, false, stop)?;
+            self.blocking_wait();
+            let consumed = self.check_operations(operations)?;
+            operations = &mut operations[consumed..];
         }
+        Ok(())
+    }
+
+    /// Execute the provided operations on the I2C bus with timeout.
+    ///
+    /// See [`blocking_transaction`].
+    #[cfg(feature = "time")]
+    pub fn blocking_transaction_timeout(
+        &mut self,
+        address: u8,
+        mut operations: &mut [Operation<'_>],
+        stop: bool,
+        timeout: Duration,
+    ) -> Result<(), Error> {
+        let mut tx_ram_buffer = [MaybeUninit::uninit(); FORCE_COPY_BUFFER_SIZE];
+        while !operations.is_empty() {
+            self.setup_operations(address, operations, Some(&mut tx_ram_buffer), false, stop)?;
+            self.blocking_wait_timeout(timeout)?;
+            let consumed = self.check_operations(operations)?;
+            operations = &mut operations[consumed..];
+        }
+        Ok(())
+    }
+
+    /// Same as [`blocking_transaction_timeout`](Twim::blocking_transaction_timeout) but will fail instead of copying data into RAM. Consult the module level documentation to learn more.
+    #[cfg(feature = "time")]
+    pub fn blocking_transaction_from_ram_timeout(
+        &mut self,
+        address: u8,
+        mut operations: &mut [Operation<'_>],
+        stop: bool,
+        timeout: Duration,
+    ) -> Result<(), Error> {
+        while !operations.is_empty() {
+            self.setup_operations(address, operations, None, false, stop)?;
+            self.blocking_wait_timeout(timeout)?;
+            let consumed = self.check_operations(operations)?;
+            operations = &mut operations[consumed..];
+        }
+        Ok(())
+    }
+
+    /// Execute the provided operations on the I2C bus.
+    ///
+    /// Each buffer must have a length of at most 255 bytes on the nRF52832
+    /// and at most 65535 bytes on the nRF52840.
+    ///
+    /// If `stop` is set, the transaction will be terminated with a STOP
+    /// condition and the Twim will be stopped. Otherwise, the bus will be
+    /// left busy via clock stretching and Twim will be suspended.
+    ///
+    /// The nrf52832, nrf5340, and nrf9120 do not have hardware support for
+    /// suspending following a read operation therefore it is emulated by the
+    /// interrupt handler. If the latency of servicing that interrupt is
+    /// longer than a byte worth of clocks on the bus, the SCL clock will
+    /// continue to run for one or more additional bytes. This applies to
+    /// consecutive read operations, certain write-read-write sequences, or
+    /// any sequence of operations ending in a read when `stop == false`.
+    pub async fn transaction(
+        &mut self,
+        address: u8,
+        mut operations: &mut [Operation<'_>],
+        stop: bool,
+    ) -> Result<(), Error> {
+        let mut tx_ram_buffer = [MaybeUninit::uninit(); FORCE_COPY_BUFFER_SIZE];
+        while !operations.is_empty() {
+            self.setup_operations(address, operations, Some(&mut tx_ram_buffer), true, stop)?;
+            self.async_wait().await;
+            let consumed = self.check_operations(operations)?;
+            operations = &mut operations[consumed..];
+        }
+        Ok(())
+    }
+
+    /// Same as [`transaction`](Twim::transaction) but will fail instead of copying data into RAM. Consult the module level documentation to learn more.
+    pub async fn transaction_from_ram(
+        &mut self,
+        address: u8,
+        mut operations: &mut [Operation<'_>],
+        stop: bool,
+    ) -> Result<(), Error> {
+        while !operations.is_empty() {
+            self.setup_operations(address, operations, None, true, stop)?;
+            self.async_wait().await;
+            let consumed = self.check_operations(operations)?;
+            operations = &mut operations[consumed..];
+        }
+        Ok(())
+    }
+
+    // ===========================================
 
     /// Write to an I2C slave.
     ///
     /// The buffer must have a length of at most 255 bytes on the nRF52832
     /// and at most 65535 bytes on the nRF52840.
     pub fn blocking_write(&mut self, address: u8, buffer: &[u8]) -> Result<(), Error> {
-        self.setup_write(address, buffer, false)?;
+        self.blocking_transaction(address, &mut [Operation::Write(buffer)], true)
-        self.blocking_wait();
-        compiler_fence(SeqCst);
-        self.check_errorsrc()?;
-        self.check_tx(buffer.len())?;
-        Ok(())
     }
 
     /// Same as [`blocking_write`](Twim::blocking_write) but will fail instead of copying data into RAM. Consult the module level documentation to learn more.
     pub fn blocking_write_from_ram(&mut self, address: u8, buffer: &[u8]) -> Result<(), Error> {
-        self.setup_write_from_ram(address, buffer, false)?;
+        self.blocking_transaction_from_ram(address, &mut [Operation::Write(buffer)], true)
-        self.blocking_wait();
-        compiler_fence(SeqCst);
-        self.check_errorsrc()?;
-        self.check_tx(buffer.len())?;
-        Ok(())
     }
 
     /// Read from an I2C slave.
@@ -516,12 +733,7 @@ impl<'d, T: Instance> Twim<'d, T> {
     /// The buffer must have a length of at most 255 bytes on the nRF52832
     /// and at most 65535 bytes on the nRF52840.
     pub fn blocking_read(&mut self, address: u8, buffer: &mut [u8]) -> Result<(), Error> {
-        self.setup_read(address, buffer, false)?;
+        self.blocking_transaction(address, &mut [Operation::Read(buffer)], true)
-        self.blocking_wait();
-        compiler_fence(SeqCst);
-        self.check_errorsrc()?;
-        self.check_rx(buffer.len())?;
-        Ok(())
     }
 
     /// Write data to an I2C slave, then read data from the slave without
@@ -530,13 +742,11 @@ impl<'d, T: Instance> Twim<'d, T> {
     /// The buffers must have a length of at most 255 bytes on the nRF52832
     /// and at most 65535 bytes on the nRF52840.
     pub fn blocking_write_read(&mut self, address: u8, wr_buffer: &[u8], rd_buffer: &mut [u8]) -> Result<(), Error> {
-        self.setup_write_read(address, wr_buffer, rd_buffer, false)?;
+        self.blocking_transaction(
-        self.blocking_wait();
+            address,
-        compiler_fence(SeqCst);
+            &mut [Operation::Write(wr_buffer), Operation::Read(rd_buffer)],
-        self.check_errorsrc()?;
+            true,
-        self.check_tx(wr_buffer.len())?;
+        )
-        self.check_rx(rd_buffer.len())?;
-        Ok(())
     }
 
     /// Same as [`blocking_write_read`](Twim::blocking_write_read) but will fail instead of copying data into RAM. Consult the module level documentation to learn more.
@@ -546,13 +756,11 @@ impl<'d, T: Instance> Twim<'d, T> {
         wr_buffer: &[u8],
         rd_buffer: &mut [u8],
     ) -> Result<(), Error> {
-        self.setup_write_read_from_ram(address, wr_buffer, rd_buffer, false)?;
+        self.blocking_transaction_from_ram(
-        self.blocking_wait();
+            address,
-        compiler_fence(SeqCst);
+            &mut [Operation::Write(wr_buffer), Operation::Read(rd_buffer)],
-        self.check_errorsrc()?;
+            true,
-        self.check_tx(wr_buffer.len())?;
+        )
-        self.check_rx(rd_buffer.len())?;
-        Ok(())
     }
 
     // ===========================================
@@ -562,12 +770,7 @@ impl<'d, T: Instance> Twim<'d, T> {
     /// See [`blocking_write`].
     #[cfg(feature = "time")]
     pub fn blocking_write_timeout(&mut self, address: u8, buffer: &[u8], timeout: Duration) -> Result<(), Error> {
-        self.setup_write(address, buffer, false)?;
+        self.blocking_transaction_timeout(address, &mut [Operation::Write(buffer)], true, timeout)
-        self.blocking_wait_timeout(timeout)?;
-        compiler_fence(SeqCst);
-        self.check_errorsrc()?;
-        self.check_tx(buffer.len())?;
-        Ok(())
     }
 
     /// Same as [`blocking_write`](Twim::blocking_write) but will fail instead of copying data into RAM. Consult the module level documentation to learn more.
@@ -578,12 +781,7 @@ impl<'d, T: Instance> Twim<'d, T> {
         buffer: &[u8],
         timeout: Duration,
     ) -> Result<(), Error> {
-        self.setup_write_from_ram(address, buffer, false)?;
+        self.blocking_transaction_from_ram_timeout(address, &mut [Operation::Write(buffer)], true, timeout)
-        self.blocking_wait_timeout(timeout)?;
-        compiler_fence(SeqCst);
-        self.check_errorsrc()?;
-        self.check_tx(buffer.len())?;
-        Ok(())
     }
 
     /// Read from an I2C slave.
@@ -592,12 +790,7 @@ impl<'d, T: Instance> Twim<'d, T> {
     /// and at most 65535 bytes on the nRF52840.
     #[cfg(feature = "time")]
     pub fn blocking_read_timeout(&mut self, address: u8, buffer: &mut [u8], timeout: Duration) -> Result<(), Error> {
-        self.setup_read(address, buffer, false)?;
+        self.blocking_transaction_timeout(address, &mut [Operation::Read(buffer)], true, timeout)
-        self.blocking_wait_timeout(timeout)?;
-        compiler_fence(SeqCst);
-        self.check_errorsrc()?;
-        self.check_rx(buffer.len())?;
-        Ok(())
     }
 
     /// Write data to an I2C slave, then read data from the slave without
@@ -613,13 +806,12 @@ impl<'d, T: Instance> Twim<'d, T> {
         rd_buffer: &mut [u8],
         timeout: Duration,
     ) -> Result<(), Error> {
-        self.setup_write_read(address, wr_buffer, rd_buffer, false)?;
+        self.blocking_transaction_timeout(
-        self.blocking_wait_timeout(timeout)?;
+            address,
-        compiler_fence(SeqCst);
+            &mut [Operation::Write(wr_buffer), Operation::Read(rd_buffer)],
-        self.check_errorsrc()?;
+            true,
-        self.check_tx(wr_buffer.len())?;
+            timeout,
-        self.check_rx(rd_buffer.len())?;
+        )
-        Ok(())
     }
 
     /// Same as [`blocking_write_read`](Twim::blocking_write_read) but will fail instead of copying data into RAM. Consult the module level documentation to learn more.
@@ -631,13 +823,12 @@ impl<'d, T: Instance> Twim<'d, T> {
         rd_buffer: &mut [u8],
         timeout: Duration,
     ) -> Result<(), Error> {
-        self.setup_write_read_from_ram(address, wr_buffer, rd_buffer, false)?;
+        self.blocking_transaction_from_ram_timeout(
-        self.blocking_wait_timeout(timeout)?;
+            address,
-        compiler_fence(SeqCst);
+            &mut [Operation::Write(wr_buffer), Operation::Read(rd_buffer)],
-        self.check_errorsrc()?;
+            true,
-        self.check_tx(wr_buffer.len())?;
+            timeout,
-        self.check_rx(rd_buffer.len())?;
+        )
-        Ok(())
     }
 
     // ===========================================
@@ -647,12 +838,7 @@ impl<'d, T: Instance> Twim<'d, T> {
     /// The buffer must have a length of at most 255 bytes on the nRF52832
     /// and at most 65535 bytes on the nRF52840.
     pub async fn read(&mut self, address: u8, buffer: &mut [u8]) -> Result<(), Error> {
-        self.setup_read(address, buffer, true)?;
+        self.transaction(address, &mut [Operation::Read(buffer)], true).await
-        self.async_wait().await;
-        compiler_fence(SeqCst);
-        self.check_errorsrc()?;
-        self.check_rx(buffer.len())?;
-        Ok(())
     }
 
     /// Write to an I2C slave.
@@ -660,22 +846,13 @@ impl<'d, T: Instance> Twim<'d, T> {
     /// The buffer must have a length of at most 255 bytes on the nRF52832
     /// and at most 65535 bytes on the nRF52840.
     pub async fn write(&mut self, address: u8, buffer: &[u8]) -> Result<(), Error> {
-        self.setup_write(address, buffer, true)?;
+        self.transaction(address, &mut [Operation::Write(buffer)], true).await
-        self.async_wait().await;
-        compiler_fence(SeqCst);
-        self.check_errorsrc()?;
-        self.check_tx(buffer.len())?;
-        Ok(())
     }
 
     /// Same as [`write`](Twim::write) but will fail instead of copying data into RAM. Consult the module level documentation to learn more.
     pub async fn write_from_ram(&mut self, address: u8, buffer: &[u8]) -> Result<(), Error> {
-        self.setup_write_from_ram(address, buffer, true)?;
+        self.transaction_from_ram(address, &mut [Operation::Write(buffer)], true)
-        self.async_wait().await;
+            .await
-        compiler_fence(SeqCst);
-        self.check_errorsrc()?;
-        self.check_tx(buffer.len())?;
-        Ok(())
     }
 
     /// Write data to an I2C slave, then read data from the slave without
@@ -684,13 +861,12 @@ impl<'d, T: Instance> Twim<'d, T> {
     /// The buffers must have a length of at most 255 bytes on the nRF52832
     /// and at most 65535 bytes on the nRF52840.
     pub async fn write_read(&mut self, address: u8, wr_buffer: &[u8], rd_buffer: &mut [u8]) -> Result<(), Error> {
-        self.setup_write_read(address, wr_buffer, rd_buffer, true)?;
+        self.transaction(
-        self.async_wait().await;
+            address,
-        compiler_fence(SeqCst);
+            &mut [Operation::Write(wr_buffer), Operation::Read(rd_buffer)],
-        self.check_errorsrc()?;
+            true,
-        self.check_tx(wr_buffer.len())?;
+        )
-        self.check_rx(rd_buffer.len())?;
+        .await
-        Ok(())
     }
 
     /// Same as [`write_read`](Twim::write_read) but will fail instead of copying data into RAM. Consult the module level documentation to learn more.
@@ -700,13 +876,12 @@ impl<'d, T: Instance> Twim<'d, T> {
         wr_buffer: &[u8],
         rd_buffer: &mut [u8],
     ) -> Result<(), Error> {
-        self.setup_write_read_from_ram(address, wr_buffer, rd_buffer, true)?;
+        self.transaction_from_ram(
-        self.async_wait().await;
+            address,
-        compiler_fence(SeqCst);
+            &mut [Operation::Write(wr_buffer), Operation::Read(rd_buffer)],
-        self.check_errorsrc()?;
+            true,
-        self.check_tx(wr_buffer.len())?;
+        )
-        self.check_rx(rd_buffer.len())?;
+        .await
-        Ok(())
     }
 }
 
@@ -777,16 +952,7 @@ mod eh02 {
         type Error = Error;
 
         fn write(&mut self, addr: u8, bytes: &[u8]) -> Result<(), Error> {
-            if slice_in_ram(bytes) {
             self.blocking_write(addr, bytes)
-            } else {
-                let buf = &mut [0; FORCE_COPY_BUFFER_SIZE][..];
-                for chunk in bytes.chunks(FORCE_COPY_BUFFER_SIZE) {
-                    buf[..chunk.len()].copy_from_slice(chunk);
-                    self.blocking_write(addr, &buf[..chunk.len()])?;
-                }
-                Ok(())
-            }
         }
     }
 
@@ -832,47 +998,14 @@ impl<'d, T: Instance> embedded_hal_1::i2c::ErrorType for Twim<'d, T> {
 }
 
 impl<'d, T: Instance> embedded_hal_1::i2c::I2c for Twim<'d, T> {
-    fn read(&mut self, address: u8, buffer: &mut [u8]) -> Result<(), Self::Error> {
+    fn transaction(&mut self, address: u8, operations: &mut [Operation<'_>]) -> Result<(), Self::Error> {
-        self.blocking_read(address, buffer)
+        self.blocking_transaction(address, operations, true)
-    }
-
-    fn write(&mut self, address: u8, buffer: &[u8]) -> Result<(), Self::Error> {
-        self.blocking_write(address, buffer)
-    }
-
-    fn write_read(&mut self, address: u8, wr_buffer: &[u8], rd_buffer: &mut [u8]) -> Result<(), Self::Error> {
-        self.blocking_write_read(address, wr_buffer, rd_buffer)
-    }
-
-    fn transaction(
-        &mut self,
-        _address: u8,
-        _operations: &mut [embedded_hal_1::i2c::Operation<'_>],
-    ) -> Result<(), Self::Error> {
-        todo!();
     }
 }
 
 impl<'d, T: Instance> embedded_hal_async::i2c::I2c for Twim<'d, T> {
-    async fn read(&mut self, address: u8, read: &mut [u8]) -> Result<(), Self::Error> {
+    async fn transaction(&mut self, address: u8, operations: &mut [Operation<'_>]) -> Result<(), Self::Error> {
-        self.read(address, read).await
+        self.transaction(address, operations, true).await
-    }
-
-    async fn write(&mut self, address: u8, write: &[u8]) -> Result<(), Self::Error> {
-        self.write(address, write).await
-    }
-    async fn write_read(&mut self, address: u8, write: &[u8], read: &mut [u8]) -> Result<(), Self::Error> {
-        self.write_read(address, write, read).await
-    }
-
-    async fn transaction(
-        &mut self,
-        address: u8,
-        operations: &mut [embedded_hal_1::i2c::Operation<'_>],
-    ) -> Result<(), Self::Error> {
-        let _ = address;
-        let _ = operations;
-        todo!()
     }
 }