async: add SPI

embedded-hal-async/src/lib.rs

@@ -10,7 +10,9 @@
 #![deny(missing_docs)]
 #![no_std]
 #![feature(generic_associated_types)]
+#![feature(type_alias_impl_trait)]
 
 pub mod delay;
 pub mod digital;
 pub mod i2c;
+pub mod spi;

embedded-hal-async/src/spi.rs

@@ -0,0 +1,324 @@
+//! Serial Peripheral Interface
+
+use core::{fmt::Debug, future::Future};
+
+pub use embedded_hal::spi::{
+    Error, ErrorKind, ErrorType, Mode, Phase, Polarity, MODE_0, MODE_1, MODE_2, MODE_3,
+};
+use embedded_hal::{digital::blocking::OutputPin, spi::blocking};
+
+/// SPI device trait
+///
+/// `SpiDevice` represents ownership over a single SPI device on a (possibly shared) bus, selected
+/// with a CS (Chip Select) pin.
+///
+/// See (the docs on embedded-hal)[embedded_hal::spi::blocking] for important information on SPI Bus vs Device traits.
+pub trait SpiDevice: ErrorType {
+    /// SPI Bus type for this device.
+    type Bus: ErrorType;
+
+    /// Future returned by the `transaction` method.
+    type TransactionFuture<'a, R, F, Fut>: Future<Output = Result<R, Self::Error>> + 'a
+    where
+        Self: 'a,
+        R: 'a,
+        F: FnOnce(&'a mut Self::Bus) -> Fut + 'a,
+        Fut: Future<
+                Output = (
+                    &'a mut Self::Bus,
+                    Result<R, <Self::Bus as ErrorType>::Error>,
+                ),
+            > + 'a;
+
+    /// Perform a transaction against the device.
+    ///
+    /// - Locks the bus
+    /// - Asserts the CS (Chip Select) pin.
+    /// - Calls `f` with an exclusive reference to the bus, which can then be used to do transfers against the device.
+    /// - [Flushes](SpiBusFlush::flush) the bus.
+    /// - Deasserts the CS pin.
+    /// - Unlocks the bus.
+    ///
+    /// The locking mechanism is implementation-defined. The only requirement is it must prevent two
+    /// transactions from executing concurrently against the same bus. Examples of implementations are:
+    /// critical sections, blocking mutexes, async mutexes, returning an error or panicking if the bus is already busy.
+    fn transaction<'a, R, F, Fut>(&'a mut self, f: F) -> Self::TransactionFuture<'a, R, F, Fut>
+    where
+        F: FnOnce(&'a mut Self::Bus) -> Fut + 'a,
+        Fut: Future<
+                Output = (
+                    &'a mut Self::Bus,
+                    Result<R, <Self::Bus as ErrorType>::Error>,
+                ),
+            > + 'a;
+}
+
+impl<T: SpiDevice> SpiDevice for &mut T {
+    type Bus = T::Bus;
+
+    type TransactionFuture<'a, R, F, Fut> = T::TransactionFuture<'a, R, F, Fut>
+    where
+        Self: 'a, R: 'a, F: FnOnce(&'a mut Self::Bus) -> Fut + 'a,
+        Fut: Future<Output = (&'a mut Self::Bus, Result<R, <Self::Bus as ErrorType>::Error>)> + 'a;
+
+    fn transaction<'a, R, F, Fut>(&'a mut self, f: F) -> Self::TransactionFuture<'a, R, F, Fut>
+    where
+        F: FnOnce(&'a mut Self::Bus) -> Fut + 'a,
+        Fut: Future<
+                Output = (
+                    &'a mut Self::Bus,
+                    Result<R, <Self::Bus as ErrorType>::Error>,
+                ),
+            > + 'a,
+    {
+        T::transaction(self, f)
+    }
+}
+
+/// Flush support for SPI bus
+pub trait SpiBusFlush: ErrorType {
+    /// Future returned by the `flush` method.
+    type FlushFuture<'a>: Future<Output = Result<(), Self::Error>> + 'a
+    where
+        Self: 'a;
+
+    /// Wait until all operations have completed and the bus is idle.
+    ///
+    /// See (the docs on embedded-hal)[embedded_hal::spi::blocking] for information on flushing.
+    fn flush<'a>(&'a mut self) -> Self::FlushFuture<'a>;
+}
+
+impl<T: SpiBusFlush> SpiBusFlush for &mut T {
+    type FlushFuture<'a> = T::FlushFuture<'a> where Self: 'a;
+
+    fn flush<'a>(&'a mut self) -> Self::FlushFuture<'a> {
+        T::flush(self)
+    }
+}
+
+/// Read-only SPI bus
+pub trait SpiBusRead<Word: 'static + Copy = u8>: SpiBusFlush {
+    /// Future returned by the `read` method.
+    type ReadFuture<'a>: Future<Output = Result<(), Self::Error>> + 'a
+    where
+        Self: 'a;
+
+    /// Read `words` from the slave.
+    ///
+    /// The word value sent on MOSI during reading is implementation-defined,
+    /// typically `0x00`, `0xFF`, or configurable.
+    ///
+    /// Implementations are allowed to return before the operation is
+    /// complete. See (the docs on embedded-hal)[embedded_hal::spi::blocking] for details on flushing.
+    fn read<'a>(&'a mut self, words: &'a mut [Word]) -> Self::ReadFuture<'a>;
+}
+
+impl<T: SpiBusRead<Word>, Word: 'static + Copy> SpiBusRead<Word> for &mut T {
+    type ReadFuture<'a> = T::ReadFuture<'a> where Self: 'a;
+
+    fn read<'a>(&'a mut self, words: &'a mut [Word]) -> Self::ReadFuture<'a> {
+        T::read(self, words)
+    }
+}
+
+/// Write-only SPI
+pub trait SpiBusWrite<Word: 'static + Copy = u8>: SpiBusFlush {
+    /// Future returned by the `write` method.
+    type WriteFuture<'a>: Future<Output = Result<(), Self::Error>> + 'a
+    where
+        Self: 'a;
+
+    /// Write `words` to the slave, ignoring all the incoming words
+    ///
+    /// Implementations are allowed to return before the operation is
+    /// complete. See (the docs on embedded-hal)[embedded_hal::spi::blocking] for details on flushing.
+    fn write<'a>(&'a mut self, words: &'a [Word]) -> Self::WriteFuture<'a>;
+}
+
+impl<T: SpiBusWrite<Word>, Word: 'static + Copy> SpiBusWrite<Word> for &mut T {
+    type WriteFuture<'a> = T::WriteFuture<'a> where Self: 'a;
+
+    fn write<'a>(&'a mut self, words: &'a [Word]) -> Self::WriteFuture<'a> {
+        T::write(self, words)
+    }
+}
+
+/// Read-write SPI bus
+///
+/// `SpiBus` represents **exclusive ownership** over the whole SPI bus, with SCK, MOSI and MISO pins.
+///
+/// See (the docs on embedded-hal)[embedded_hal::spi::blocking] for important information on SPI Bus vs Device traits.
+pub trait SpiBus<Word: 'static + Copy = u8>: SpiBusRead<Word> + SpiBusWrite<Word> {
+    /// Future returned by the `transfer` method.
+    type TransferFuture<'a>: Future<Output = Result<(), Self::Error>> + 'a
+    where
+        Self: 'a;
+
+    /// Write and read simultaneously. `write` is written to the slave on MOSI and
+    /// words received on MISO are stored in `read`.
+    ///
+    /// It is allowed for `read` and `write` to have different lengths, even zero length.
+    /// The transfer runs for `max(read.len(), write.len())` words. If `read` is shorter,
+    /// incoming words after `read` has been filled will be discarded. If `write` is shorter,
+    /// the value of words sent in MOSI after all `write` has been sent is implementation-defined,
+    /// typically `0x00`, `0xFF`, or configurable.
+    ///
+    /// Implementations are allowed to return before the operation is
+    /// complete. See (the docs on embedded-hal)[embedded_hal::spi::blocking] for details on flushing.
+    fn transfer<'a>(
+        &'a mut self,
+        read: &'a mut [Word],
+        write: &'a [Word],
+    ) -> Self::TransferFuture<'a>;
+
+    /// Future returned by the `transfer_in_place` method.
+    type TransferInPlaceFuture<'a>: Future<Output = Result<(), Self::Error>> + 'a
+    where
+        Self: 'a;
+
+    /// Write and read simultaneously. The contents of `words` are
+    /// written to the slave, and the received words are stored into the same
+    /// `words` buffer, overwriting it.
+    ///
+    /// Implementations are allowed to return before the operation is
+    /// complete. See (the docs on embedded-hal)[embedded_hal::spi::blocking] for details on flushing.
+    fn transfer_in_place<'a>(
+        &'a mut self,
+        words: &'a mut [Word],
+    ) -> Self::TransferInPlaceFuture<'a>;
+}
+
+impl<T: SpiBus<Word>, Word: 'static + Copy> SpiBus<Word> for &mut T {
+    type TransferFuture<'a> = T::TransferFuture<'a> where Self: 'a;
+
+    fn transfer<'a>(
+        &'a mut self,
+        read: &'a mut [Word],
+        write: &'a [Word],
+    ) -> Self::TransferFuture<'a> {
+        T::transfer(self, read, write)
+    }
+
+    type TransferInPlaceFuture<'a> = T::TransferInPlaceFuture<'a> where Self: 'a;
+
+    fn transfer_in_place<'a>(
+        &'a mut self,
+        words: &'a mut [Word],
+    ) -> Self::TransferInPlaceFuture<'a> {
+        T::transfer_in_place(self, words)
+    }
+}
+
+/// Error type for [`ExclusiveDevice`] operations.
+#[derive(Copy, Clone, Eq, PartialEq, Debug)]
+pub enum ExclusiveDeviceError<BUS, CS> {
+    /// An inner SPI bus operation failed
+    Spi(BUS),
+    /// Asserting or deasserting CS failed
+    Cs(CS),
+}
+
+impl<BUS, CS> Error for ExclusiveDeviceError<BUS, CS>
+where
+    BUS: Error + Debug,
+    CS: Debug,
+{
+    fn kind(&self) -> ErrorKind {
+        match self {
+            Self::Spi(e) => e.kind(),
+            Self::Cs(_) => ErrorKind::ChipSelectFault,
+        }
+    }
+}
+
+/// [`SpiDevice`] implementation with exclusive access to the bus (not shared).
+///
+/// This is the most straightforward way of obtaining an [`SpiDevice`] from an [`SpiBus`],
+/// ideal for when no sharing is required (only one SPI device is present on the bus).
+pub struct ExclusiveDevice<BUS, CS> {
+    bus: BUS,
+    cs: CS,
+}
+
+impl<BUS, CS> ExclusiveDevice<BUS, CS> {
+    /// Create a new ExclusiveDevice
+    pub fn new(bus: BUS, cs: CS) -> Self {
+        Self { bus, cs }
+    }
+}
+
+impl<BUS, CS> ErrorType for ExclusiveDevice<BUS, CS>
+where
+    BUS: ErrorType,
+    CS: OutputPin,
+{
+    type Error = ExclusiveDeviceError<BUS::Error, CS::Error>;
+}
+
+impl<BUS, CS> blocking::SpiDevice for ExclusiveDevice<BUS, CS>
+where
+    BUS: blocking::SpiBusFlush,
+    CS: OutputPin,
+{
+    type Bus = BUS;
+
+    fn transaction<R>(
+        &mut self,
+        f: impl FnOnce(&mut Self::Bus) -> Result<R, <Self::Bus as ErrorType>::Error>,
+    ) -> Result<R, Self::Error> {
+        self.cs.set_low().map_err(ExclusiveDeviceError::Cs)?;
+
+        let f_res = f(&mut self.bus);
+
+        // On failure, it's important to still flush and deassert CS.
+        let flush_res = self.bus.flush();
+        let cs_res = self.cs.set_high();
+
+        let f_res = f_res.map_err(ExclusiveDeviceError::Spi)?;
+        flush_res.map_err(ExclusiveDeviceError::Spi)?;
+        cs_res.map_err(ExclusiveDeviceError::Cs)?;
+
+        Ok(f_res)
+    }
+}
+
+impl<BUS, CS> SpiDevice for ExclusiveDevice<BUS, CS>
+where
+    BUS: SpiBusFlush,
+    CS: OutputPin,
+{
+    type Bus = BUS;
+
+    type TransactionFuture<'a, R, F, Fut> = impl Future<Output = Result<R, Self::Error>> + 'a
+    where
+        Self: 'a, R: 'a, F: FnOnce(&'a mut Self::Bus) -> Fut + 'a,
+        Fut: Future<Output = (&'a mut Self::Bus, Result<R, <Self::Bus as ErrorType>::Error>)> + 'a;
+
+    fn transaction<'a, R, F, Fut>(&'a mut self, f: F) -> Self::TransactionFuture<'a, R, F, Fut>
+    where
+        R: 'a,
+        F: FnOnce(&'a mut Self::Bus) -> Fut + 'a,
+        Fut: Future<
+                Output = (
+                    &'a mut Self::Bus,
+                    Result<R, <Self::Bus as ErrorType>::Error>,
+                ),
+            > + 'a,
+    {
+        async move {
+            self.cs.set_low().map_err(ExclusiveDeviceError::Cs)?;
+
+            let (bus, f_res) = f(&mut self.bus).await;
+
+            // On failure, it's important to still flush and deassert CS.
+            let flush_res = bus.flush().await;
+            let cs_res = self.cs.set_high();
+
+            let f_res = f_res.map_err(ExclusiveDeviceError::Spi)?;
+            flush_res.map_err(ExclusiveDeviceError::Spi)?;
+            cs_res.map_err(ExclusiveDeviceError::Cs)?;
+
+            Ok(f_res)
+        }
+    }
+}