2 files changed, 36 insertions, 42 deletions

diff --git a/embassy-stm32f4-examples/src/serial.rs b/embassy-stm32f4-examples/src/serial.rs
index baed2e525..ea0497016 100644
--- a/embassy-stm32f4-examples/src/serial.rs
+++ b/embassy-stm32f4-examples/src/serial.rs
@@ -8,6 +8,7 @@
 use cortex_m::singleton;
 use cortex_m_rt::entry;
 use embassy::executor::{task, Executor};
+use embassy::uart::Uart;
 use embassy::util::Forever;
 use embassy_stm32f4::interrupt;
 use embassy_stm32f4::serial;
@@ -27,23 +28,23 @@ async fn run(dp: stm32::Peripherals, cp: cortex_m::Peripherals) {
         .pclk1(24.mhz())
         .freeze();
 
-    let mut serial = serial::Serial::new(
-        gpioa.pa9.into_alternate_af7(),
-        gpioa.pa10.into_alternate_af7(),
-        interrupt::take!(DMA2_STREAM7),
-        interrupt::take!(DMA2_STREAM2),
-        interrupt::take!(USART1),
-        dp.DMA2,
-        dp.USART1,
-        config::Parity::ParityNone,
-        9600.bps(),
-        clocks,
-    );
-
+    let mut serial = unsafe {
+        serial::Serial::new(
+            gpioa.pa9.into_alternate_af7(),
+            gpioa.pa10.into_alternate_af7(),
+            interrupt::take!(DMA2_STREAM7),
+            interrupt::take!(DMA2_STREAM2),
+            interrupt::take!(USART1),
+            dp.DMA2,
+            dp.USART1,
+            config::Parity::ParityNone,
+            9600.bps(),
+            clocks,
+        )
+    };
     let buf = singleton!(: [u8; 30] = [0; 30]).unwrap();
 
     buf[5] = 0x01;
-
     serial.send(buf).await;
 }
 
diff --git a/embassy-stm32f4/src/serial.rs b/embassy-stm32f4/src/serial.rs
index 01348e32b..7590fe65a 100644
--- a/embassy-stm32f4/src/serial.rs
+++ b/embassy-stm32f4/src/serial.rs
@@ -10,8 +10,9 @@ use core::sync::atomic::{self, Ordering};
 use core::task::{Context, Poll};
 
 use embassy::interrupt::OwnedInterrupt;
+use embassy::uart::{Error, Uart};
 use embassy::util::Signal;
-use embedded_dma::{StaticReadBuffer, StaticWriteBuffer, WriteBuffer};
+use embedded_dma::StaticWriteBuffer;
 
 use crate::hal::dma::config::DmaConfig;
 use crate::hal::dma::traits::{PeriAddress, Stream};
@@ -56,7 +57,8 @@ static STATE: State = State {
 static mut INSTANCE: *const Serial<USART1, Stream7<DMA2>, Stream2<DMA2>> = ptr::null_mut();
 
 impl Serial<USART1, Stream7<DMA2>, Stream2<DMA2>> {
-    pub fn new(
+    // Leaking futures is forbidden!
+    pub unsafe fn new(
         txd: PA9<Alternate<AF7>>,
         rxd: PA10<Alternate<AF7>>,
         tx_int: interrupt::DMA2_STREAM7Interrupt,
@@ -135,18 +137,19 @@ impl Serial<USART1, Stream7<DMA2>, Stream2<DMA2>> {
 
         STATE.rx_int.signal(());
     }
+}
+
+impl Uart for Serial<USART1, Stream7<DMA2>, Stream2<DMA2>> {
+    type SendFuture<'a> = impl Future<Output = Result<(), Error>> + 'a;
+    type ReceiveFuture<'a> = impl Future<Output = Result<(), Error>> + 'a;
 
     /// Sends serial data.
-    ///
-    /// `tx_buffer` is marked as static as per `embedded-dma` requirements.
-    /// It it safe to use a buffer with a non static lifetime if memory is not
-    /// reused until the future has finished.
-    pub fn send<'a, B: 'a>(&'a mut self, tx_buffer: B) -> impl Future<Output = ()> + 'a
-    where
-        B: StaticWriteBuffer<Word = u8>,
-    {
+    fn send<'a>(&'a mut self, buf: &'a [u8]) -> Self::SendFuture<'a> {
         unsafe { INSTANCE = self };
 
+        #[allow(mutable_transmutes)]
+        let static_buf = unsafe { core::mem::transmute::<&'a [u8], &'static mut [u8]>(buf) };
+
         let tx_stream = self.tx_stream.take().unwrap();
         let usart = self.usart.take().unwrap();
         STATE.tx_int.reset();
@@ -155,7 +158,7 @@ impl Serial<USART1, Stream7<DMA2>, Stream2<DMA2>> {
             let mut tx_transfer = Transfer::init(
                 tx_stream,
                 usart,
-                tx_buffer,
+                static_buf,
                 None,
                 DmaConfig::default()
                     .transfer_complete_interrupt(true)
@@ -172,6 +175,8 @@ impl Serial<USART1, Stream7<DMA2>, Stream2<DMA2>> {
             let (tx_stream, usart, _buf, _) = tx_transfer.free();
             self.tx_stream.replace(tx_stream);
             self.usart.replace(usart);
+
+            Ok(())
         }
     }
 
@@ -181,44 +186,32 @@ impl Serial<USART1, Stream7<DMA2>, Stream2<DMA2>> {
     /// A common pattern is to use [`stop()`](ReceiveFuture::stop) to cancel
     /// unfinished transfers after a timeout to prevent lockup when no more data
     /// is incoming.
-    ///
-    /// `rx_buffer` is marked as static as per `embedded-dma` requirements.
-    /// It it safe to use a buffer with a non static lifetime if memory is not
-    /// reused until the future has finished.
-    pub fn receive<'a, B: 'a>(&'a mut self, rx_buffer: B) -> impl Future<Output = B> + 'a
-    where
-        B: StaticWriteBuffer<Word = u8> + Unpin,
-    {
+    fn receive<'a>(&'a mut self, buf: &'a mut [u8]) -> Self::ReceiveFuture<'a> {
         unsafe { INSTANCE = self };
 
+        let static_buf = unsafe { core::mem::transmute::<&'a mut [u8], &'static mut [u8]>(buf) };
         let rx_stream = self.rx_stream.take().unwrap();
         let usart = self.usart.take().unwrap();
         STATE.rx_int.reset();
-
         async move {
             let mut rx_transfer = Transfer::init(
                 rx_stream,
                 usart,
-                rx_buffer,
+                static_buf,
                 None,
                 DmaConfig::default()
                     .transfer_complete_interrupt(true)
                     .memory_increment(true)
                     .double_buffer(false),
             );
-
             self.rx_int.unpend();
             self.rx_int.enable();
-
             rx_transfer.start(|_usart| {});
-
             STATE.rx_int.wait().await;
-
-            let (rx_stream, usart, buf, _) = rx_transfer.free();
+            let (rx_stream, usart, _, _) = rx_transfer.free();
             self.rx_stream.replace(rx_stream);
             self.usart.replace(usart);
-
-            buf
+            Ok(())
         }
     }
 }