feat(stm32): Let uart implement embedded-io Read/Write

embassy-stm32/src/usart/mod.rs

@@ -910,6 +910,46 @@ mod eh1 {
     }
 }
 
+#[cfg(all(feature = "unstable-traits", feature = "nightly"))]
+mod eio {
+    use embedded_io::asynch::{Read, Write};
+    use embedded_io::Io;
+
+    use super::*;
+
+    impl<T, TxDma, RxDma> Io for Uart<'_, T, TxDma, RxDma>
+    where
+        T: BasicInstance,
+    {
+        type Error = Error;
+    }
+
+    impl<T, TxDma, RxDma> Read for Uart<'_, T, TxDma, RxDma>
+    where
+        T: BasicInstance,
+        RxDma: super::RxDma<T>,
+    {
+        async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
+            self.read_until_idle(buf).await
+        }
+    }
+
+    impl<T, TxDma, RxDma> Write for Uart<'_, T, TxDma, RxDma>
+    where
+        T: BasicInstance,
+        TxDma: super::TxDma<T>,
+    {
+        async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
+            self.write(buf).await?;
+            Ok(buf.len())
+        }
+
+        async fn flush(&mut self) -> Result<(), Self::Error> {
+            self.blocking_flush()
+        }
+    }
+}
+
 #[cfg(all(
     feature = "unstable-traits",
     feature = "nightly",