add spi trait

embassy-traits/src/lib.rs

@@ -10,4 +10,5 @@ pub mod delay;
 pub mod flash;
 pub mod gpio;
 pub mod i2c;
+pub mod spi;
 pub mod uart;

embassy-traits/src/spi.rs

@@ -0,0 +1,36 @@
+//! Async SPI API
+
+use core::future::Future;
+
+/// Full duplex (master mode)
+///
+/// # Notes
+///
+/// - It's the task of the user of this interface to manage the slave select lines
+///
+/// - Due to how full duplex SPI works each `try_read` call must be preceded by a `try_send` call.
+///
+/// - `try_read` calls only return the data received with the last `try_send` call.
+/// Previously received data is discarded
+///
+/// - Data is only guaranteed to be clocked out when the `try_read` call succeeds.
+/// The slave select line shouldn't be released before that.
+///
+/// - Some SPIs can work with 8-bit *and* 16-bit words. You can overload this trait with different
+/// `Word` types to allow operation in both modes.
+pub trait FullDuplex<Word> {
+    /// An enumeration of SPI errors
+    type Error;
+
+    type WriteFuture<'a>: Future<Output = Result<(), Self::Error>> + 'a;
+    type ReadFuture<'a>: Future<Output = Result<(), Self::Error>> + 'a;
+    type WriteReadFuture<'a>: Future<Output = Result<(), Self::Error>> + 'a;
+
+    fn read<'a>(&'a mut self, data: &'a mut [Word]) -> Self::ReadFuture<'_>;
+    fn write<'a>(&'a mut self, data: &'a [Word]) -> Self::WriteFuture<'_>;
+    fn read_write<'a>(
+        &mut self,
+        read: &'a mut [Word],
+        write: &'a [Word],
+    ) -> Self::WriteReadFuture<'_>;
+}