Fail RMT one-shot transactions if end-marker is missing (#2463)

* Fail RMT one-shot transactions if end-marker is missing

* CHANGELOG.md

* Add test

* Fix

* Fix

* RMT: use u32, turn PulseCode into a convenience trait

* Clippy

* Adapt test

esp-hal/CHANGELOG.md

@@ -62,6 +62,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `slave::Spi` constructors no longer take pins (#2485)
 - The `I2c` master driver has been moved from `esp_hal::i2c` to `esp_hal::i2c::master`. (#2476)
 - `I2c` SCL timeout is now defined in bus clock cycles. (#2477)
+- Trying to send a single-shot RMT transmission will result in an error now, `RMT` deals with `u32` now, `PulseCode` is a convenience trait now (#2463)
 
 ### Fixed
 

esp-hal/MIGRATING-0.21.md

@@ -368,3 +368,31 @@ If you were using an 16-bit bus, you don't need to change anything, `set_byte_or
 
 If you were sharing the bus between an 8-bit and 16-bit device, you will have to call the corresponding method when
 you switch between devices. Be sure to read the documentation of the new methods.
+
+
+## `rmt::Channel::transmit` now returns `Result`, `PulseCode` is now `u32`
+
+When trying to send a one-shot transmission will fail if it doesn't end with an end-marker.
+
+```diff
+-    let mut data = [PulseCode {
+-        level1: true,
+-        length1: 200,
+-        level2: false,
+-        length2: 50,
+-    }; 20];
+-
+-    data[data.len() - 2] = PulseCode {
+-        level1: true,
+-        length1: 3000,
+-        level2: false,
+-        length2: 500,
+-    };
+-    data[data.len() - 1] = PulseCode::default();
++    let mut data = [PulseCode::new(true, 200, false, 50); 20];
++    data[data.len() - 2] = PulseCode::new(true, 3000, false, 500);
++    data[data.len() - 1] = PulseCode::empty();
+
+-        let transaction = channel.transmit(&data);
++        let transaction = channel.transmit(&data).unwrap();
+```

esp-hal/src/rmt.rs

@@ -112,61 +112,62 @@ pub enum Error {
     InvalidArgument,
     /// An error occurred during transmission
     TransmissionError,
+    /// No transmission end marker found
+    EndMarkerMissing,
 }
 
-/// Convenience representation of a pulse code entry.
-///
-/// Allows for the assignment of two levels and their lengths
-#[derive(Clone, Copy, Debug, Default, PartialEq)]
-#[cfg_attr(feature = "defmt", derive(defmt::Format))]
-pub struct PulseCode {
+///  Convenience trait to work with pulse codes.
+pub trait PulseCode: crate::private::Sealed {
+    /// Create a new instance
+    fn new(level1: bool, length1: u16, level2: bool, length2: u16) -> Self;
+
+    /// Create a new empty instance
+    fn empty() -> Self;
+
+    /// Set all levels and lengths to 0
+    fn reset(&mut self);
+
     /// Logical output level in the first pulse code interval
-    pub level1: bool,
+    fn level1(&self) -> bool;
+
     /// Length of the first pulse code interval (in clock cycles)
-    pub length1: u16,
+    fn length1(&self) -> u16;
+
     /// Logical output level in the second pulse code interval
-    pub level2: bool,
+    fn level2(&self) -> bool;
+
     /// Length of the second pulse code interval (in clock cycles)
-    pub length2: u16,
+    fn length2(&self) -> u16;
 }
 
-impl From<u32> for PulseCode {
-    fn from(value: u32) -> Self {
-        Self {
-            level1: value & (1 << 15) != 0,
-            length1: (value & 0b111_1111_1111_1111) as u16,
-            level2: value & (1 << 31) != 0,
-            length2: ((value >> 16) & 0b111_1111_1111_1111) as u16,
-        }
+impl PulseCode for u32 {
+    fn new(level1: bool, length1: u16, level2: bool, length2: u16) -> Self {
+        (((level1 as u32) << 15) | length1 as u32 & 0b111_1111_1111_1111)
+            | (((level2 as u32) << 15) | length2 as u32 & 0b111_1111_1111_1111) << 16
     }
-}
 
-/// Convert a pulse code structure into a u32 value that can be written
-/// into the data registers
-impl From<PulseCode> for u32 {
-    #[inline(always)]
-    fn from(p: PulseCode) -> u32 {
-        // The length1 value resides in bits [14:0]
-        let mut entry: u32 = p.length1 as u32;
-
-        // If level1 is high, set bit 15, otherwise clear it
-        if p.level1 {
-            entry |= 1 << 15;
-        } else {
-            entry &= !(1 << 15);
-        }
+    fn empty() -> Self {
+        0
+    }
 
-        // If level2 is high, set bit 31, otherwise clear it
-        if p.level2 {
-            entry |= 1 << 31;
-        } else {
-            entry &= !(1 << 31);
-        }
+    fn reset(&mut self) {
+        *self = 0
+    }
 
-        // The length2 value resides in bits [30:16]
-        entry |= (p.length2 as u32) << 16;
+    fn level1(&self) -> bool {
+        self & (1 << 15) != 0
+    }
+
+    fn length1(&self) -> u16 {
+        (self & 0b111_1111_1111_1111) as u16
+    }
+
+    fn level2(&self) -> bool {
+        self & (1 << 31) != 0
+    }
 
-        entry
+    fn length2(&self) -> u16 {
+        ((self >> 16) & 0b111_1111_1111_1111) as u16
     }
 }
 
@@ -423,16 +424,16 @@ where
 }
 
 /// An in-progress transaction for a single shot TX transaction.
-pub struct SingleShotTxTransaction<'a, C, T: Into<u32> + Copy>
+pub struct SingleShotTxTransaction<'a, C>
 where
     C: TxChannel,
 {
     channel: C,
     index: usize,
-    data: &'a [T],
+    data: &'a [u32],
 }
 
-impl<C, T: Into<u32> + Copy> SingleShotTxTransaction<'_, C, T>
+impl<C> SingleShotTxTransaction<'_, C>
 where
     C: TxChannel,
 {
@@ -466,7 +467,7 @@ where
                 .enumerate()
             {
                 unsafe {
-                    ptr.add(idx).write_volatile((*entry).into());
+                    ptr.add(idx).write_volatile(*entry);
                 }
             }
 
@@ -982,26 +983,23 @@ pub trait TxChannel: TxChannelInternal<Blocking> {
     /// This returns a [`SingleShotTxTransaction`] which can be used to wait for
     /// the transaction to complete and get back the channel for further
     /// use.
-    fn transmit<T: Into<u32> + Copy>(self, data: &[T]) -> SingleShotTxTransaction<'_, Self, T>
+    fn transmit(self, data: &[u32]) -> Result<SingleShotTxTransaction<'_, Self>, Error>
     where
         Self: Sized,
     {
-        let index = Self::send_raw(data, false, 0);
-        SingleShotTxTransaction {
+        let index = Self::send_raw(data, false, 0)?;
+        Ok(SingleShotTxTransaction {
             channel: self,
             index,
             data,
-        }
+        })
     }
 
     /// Start transmitting the given pulse code continuously.
     /// This returns a [`ContinuousTxTransaction`] which can be used to stop the
     /// ongoing transmission and get back the channel for further use.
     /// The length of sequence cannot exceed the size of the allocated RMT RAM.
-    fn transmit_continuously<T: Into<u32> + Copy>(
-        self,
-        data: &[T],
-    ) -> Result<ContinuousTxTransaction<Self>, Error>
+    fn transmit_continuously(self, data: &[u32]) -> Result<ContinuousTxTransaction<Self>, Error>
     where
         Self: Sized,
     {
@@ -1011,10 +1009,10 @@ pub trait TxChannel: TxChannelInternal<Blocking> {
     /// Like [`Self::transmit_continuously`] but also sets a loop count.
     /// [`ContinuousTxTransaction`] can be used to check if the loop count is
     /// reached.
-    fn transmit_continuously_with_loopcount<T: Into<u32> + Copy>(
+    fn transmit_continuously_with_loopcount(
         self,
         loopcount: u16,
-        data: &[T],
+        data: &[u32],
     ) -> Result<ContinuousTxTransaction<Self>, Error>
     where
         Self: Sized,
@@ -1023,21 +1021,21 @@ pub trait TxChannel: TxChannelInternal<Blocking> {
             return Err(Error::Overflow);
         }
 
-        let _index = Self::send_raw(data, true, loopcount);
+        let _index = Self::send_raw(data, true, loopcount)?;
         Ok(ContinuousTxTransaction { channel: self })
     }
 }
 
 /// RX transaction instance
-pub struct RxTransaction<'a, C, T: From<u32> + Copy>
+pub struct RxTransaction<'a, C>
 where
     C: RxChannel,
 {
     channel: C,
-    data: &'a mut [T],
+    data: &'a mut [u32],
 }
 
-impl<C, T: From<u32> + Copy> RxTransaction<'_, C, T>
+impl<C> RxTransaction<'_, C>
 where
     C: RxChannel,
 {
@@ -1062,7 +1060,7 @@ where
             as *mut u32;
         let len = self.data.len();
         for (idx, entry) in self.data.iter_mut().take(len).enumerate() {
-            *entry = unsafe { ptr.add(idx).read_volatile().into() };
+            *entry = unsafe { ptr.add(idx).read_volatile() };
         }
 
         Ok(self.channel)
@@ -1075,10 +1073,7 @@ pub trait RxChannel: RxChannelInternal<Blocking> {
     /// This returns a [RxTransaction] which can be used to wait for receive to
     /// complete and get back the channel for further use.
     /// The length of the received data cannot exceed the allocated RMT RAM.
-    fn receive<T: From<u32> + Copy>(
-        self,
-        data: &mut [T],
-    ) -> Result<RxTransaction<'_, Self, T>, Error>
+    fn receive(self, data: &mut [u32]) -> Result<RxTransaction<'_, Self>, Error>
     where
         Self: Sized,
     {
@@ -1143,7 +1138,7 @@ pub trait TxChannelAsync: TxChannelInternal<Async> {
     /// Start transmitting the given pulse code sequence.
     /// The length of sequence cannot exceed the size of the allocated RMT
     /// RAM.
-    async fn transmit<'a, T: Into<u32> + Copy>(&mut self, data: &'a [T]) -> Result<(), Error>
+    async fn transmit<'a>(&mut self, data: &'a [u32]) -> Result<(), Error>
     where
         Self: Sized,
     {
@@ -1154,7 +1149,7 @@ pub trait TxChannelAsync: TxChannelInternal<Async> {
         Self::clear_interrupts();
         Self::listen_interrupt(Event::End);
         Self::listen_interrupt(Event::Error);
-        Self::send_raw(data, false, 0);
+        Self::send_raw(data, false, 0)?;
 
         RmtTxFuture::new(self).await;
 
@@ -1402,9 +1397,17 @@ where
 
     fn is_loopcount_interrupt_set() -> bool;
 
-    fn send_raw<T: Into<u32> + Copy>(data: &[T], continuous: bool, repeat: u16) -> usize {
+    fn send_raw(data: &[u32], continuous: bool, repeat: u16) -> Result<usize, Error> {
         Self::clear_interrupts();
 
+        if let Some(last) = data.last() {
+            if !continuous && last.length2() != 0 && last.length1() != 0 {
+                return Err(Error::EndMarkerMissing);
+            }
+        } else {
+            return Err(Error::InvalidArgument);
+        }
+
         let ptr = (constants::RMT_RAM_START
             + Self::CHANNEL as usize * constants::RMT_CHANNEL_RAM_SIZE * 4)
             as *mut u32;
@@ -1414,7 +1417,7 @@ where
             .enumerate()
         {
             unsafe {
-                ptr.add(idx).write_volatile((*entry).into());
+                ptr.add(idx).write_volatile(*entry);
             }
         }
 
@@ -1428,9 +1431,9 @@ where
         Self::update();
 
         if data.len() >= constants::RMT_CHANNEL_RAM_SIZE {
-            constants::RMT_CHANNEL_RAM_SIZE
+            Ok(constants::RMT_CHANNEL_RAM_SIZE)
         } else {
-            data.len()
+            Ok(data.len())
         }
     }
 

examples/src/bin/embassy_rmt_rx.rs

@@ -73,46 +73,41 @@ async fn main(spawner: Spawner) {
         .spawn(signal_task(Output::new(peripherals.GPIO5, Level::Low)))
         .unwrap();
 
-    let mut data = [PulseCode {
-        level1: true,
-        length1: 1,
-        level2: false,
-        length2: 1,
-    }; 48];
+    let mut data: [u32; 48] = [PulseCode::empty(); 48];
 
     loop {
         println!("receive");
         channel.receive(&mut data).await.unwrap();
         let mut total = 0usize;
         for entry in &data[..data.len()] {
-            if entry.length1 == 0 {
+            if entry.length1() == 0 {
                 break;
             }
-            total += entry.length1 as usize;
+            total += entry.length1() as usize;
 
-            if entry.length2 == 0 {
+            if entry.length2() == 0 {
                 break;
             }
-            total += entry.length2 as usize;
+            total += entry.length2() as usize;
         }
 
         for entry in &data[..data.len()] {
-            if entry.length1 == 0 {
+            if entry.length1() == 0 {
                 break;
             }
 
-            let count = WIDTH / (total / entry.length1 as usize);
-            let c = if entry.level1 { '-' } else { '_' };
+            let count = WIDTH / (total / entry.length1() as usize);
+            let c = if entry.level1() { '-' } else { '_' };
             for _ in 0..count + 1 {
                 print!("{}", c);
             }
 
-            if entry.length2 == 0 {
+            if entry.length2() == 0 {
                 break;
             }
 
-            let count = WIDTH / (total / entry.length2 as usize);
-            let c = if entry.level2 { '-' } else { '_' };
+            let count = WIDTH / (total / entry.length2() as usize);
+            let c = if entry.level2() { '-' } else { '_' };
             for _ in 0..count + 1 {
                 print!("{}", c);
             }