Add non-blocking spi send trait

Author: david-sawatzke

Diff for: src/prelude.rs

@@ -28,6 +28,8 @@ pub use digital::ToggleableOutputPin as _embedded_hal_digital_ToggleableOutputPi
 pub use serial::Read as _embedded_hal_serial_Read;
 pub use serial::Write as _embedded_hal_serial_Write;
 pub use spi::FullDuplex as _embedded_hal_spi_FullDuplex;
+#[cfg(feature = "unproven")]
+pub use spi::Send as _embedded_hal_spi_Send;
 pub use timer::CountDown as _embedded_hal_timer_CountDown;
 #[cfg(feature = "unproven")]
 pub use watchdog::Watchdog as _embedded_hal_watchdog_Watchdog;

Diff for: src/spi.rs

@@ -26,6 +26,52 @@ pub trait FullDuplex<Word> {
     fn send(&mut self, word: Word) -> nb::Result<(), Self::Error>;
 }
 
+/// Write (master mode)
+///
+/// # Notes
+///
+/// - It's the task of the user of this interface to manage the slave select lines
+#[cfg(feature = "unproven")]
+pub trait Send<Word> {
+    /// An enumeration of SPI errors
+    type Error;
+
+    /// Sends a word to the slave
+    fn send(&mut self, word: Word) -> nb::Result<(), Self::Error>;
+}
+
+/// Write (master mode)
+#[cfg(feature = "unproven")]
+pub mod full_duplex {
+    /// Default implementation of `spi::FullDuplex<W>` for implementers of
+    /// `spi::Send<W>`
+    ///
+    /// Also needs a `send` method to return the byte read during the last send
+    pub trait Default<W>: ::spi::Send<W> {
+        /// Reads the word stored in the shift register
+        ///
+        /// **NOTE** A word must be sent to the slave before attempting to call this
+        /// method.
+        fn read(&mut self) -> nb::Result<W, Self::Error>;
+    }
+
+    impl<W, S> ::spi::FullDuplex<W> for S
+    where
+        S: Default<W>,
+        W: Clone,
+    {
+        type Error = S::Error;
+
+        fn read(&mut self) -> nb::Result<W, Self::Error> {
+            self.read()
+        }
+
+        fn send(&mut self, word: W) -> nb::Result<(), Self::Error> {
+            self.send(word)
+        }
+    }
+}
+
 /// Clock polarity
 #[derive(Clone, Copy, PartialEq)]
 pub enum Polarity {
@@ -75,4 +121,4 @@ pub const MODE_2: Mode = Mode {
 pub const MODE_3: Mode = Mode {
     polarity: Polarity::IdleHigh,
     phase: Phase::CaptureOnSecondTransition,
-};
+};