Add Uart trait, implement it for nrf.

embassy/src/lib.rs

@@ -12,4 +12,5 @@ pub mod interrupt;
 pub mod io;
 pub mod rand;
 pub mod time;
+pub mod uart;
 pub mod util;

embassy/src/uart.rs

@@ -0,0 +1,15 @@
+use core::future::Future;
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[non_exhaustive]
+pub enum Error {
+    Other,
+}
+
+pub trait Uart {
+    type ReceiveFuture<'a>: Future<Output = Result<(), Error>>;
+    type SendFuture<'a>: Future<Output = Result<(), Error>>;
+    fn receive<'a>(&'a mut self, buf: &'a mut [u8]) -> Self::ReceiveFuture<'a>;
+    fn send<'a>(&'a mut self, buf: &'a [u8]) -> Self::SendFuture<'a>;
+}