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//! SPI master mode traits.
use core::{fmt::Debug, future::Future};
use embedded_hal::digital::OutputPin;
use embedded_hal::spi as blocking;
pub use embedded_hal::spi::{
Error, ErrorKind, ErrorType, Mode, Phase, Polarity, MODE_0, MODE_1, MODE_2, MODE_3,
};
#[macro_export]
/// Do an SPI transaction on a bus.
/// This is a safe wrapper for [SpiDevice::transaction], which handles dereferencing the raw pointer for you.
///
/// # Examples
///
/// ```
/// use embedded_hal_async::spi::{transaction, SpiBus, SpiBusRead, SpiBusWrite, SpiDevice};
///
/// pub async fn transaction_example<SPI>(mut device: SPI) -> Result<u32, SPI::Error>
/// where
/// SPI: SpiDevice,
/// SPI::Bus: SpiBus,
/// {
/// transaction!(&mut device, move |bus| async move {
/// // Unlike `SpiDevice::transaction`, we don't need to
/// // manually dereference a pointer in order to use the bus.
/// bus.write(&[42]).await?;
/// let mut data = [0; 4];
/// bus.read(&mut data).await?;
/// Ok(u32::from_be_bytes(data))
/// })
/// .await
/// }
/// ```
///
/// Note that the compiler will prevent you from moving the bus reference outside of the closure
/// ```compile_fail
/// # use embedded_hal_async::spi::{transaction, SpiBus, SpiBusRead, SpiBusWrite, SpiDevice};
/// #
/// # pub async fn smuggle_test<SPI>(mut device: SPI) -> Result<(), SPI::Error>
/// # where
/// # SPI: SpiDevice,
/// # SPI::Bus: SpiBus,
/// # {
/// let mut bus_smuggler: Option<&mut SPI::Bus> = None;
/// transaction!(&mut device, move |bus| async move {
/// bus_smuggler = Some(bus);
/// Ok(())
/// })
/// .await
/// # }
/// ```
macro_rules! spi_transaction {
($device:expr, move |$bus:ident| async move $closure_body:expr) => {
$crate::spi::SpiDevice::transaction($device, move |$bus| {
// Safety: Implementers of the `SpiDevice` trait guarantee that the pointer is
// valid and dereferencable for the entire duration of the closure.
let $bus = unsafe { &mut *$bus };
async move {
let result = $closure_body;
let $bus = $bus; // Ensure that the bus reference was not moved out of the closure
let _ = $bus; // Silence the "unused variable" warning from prevous line
result
}
})
};
($device:expr, move |$bus:ident| async $closure_body:expr) => {
$crate::spi::SpiDevice::transaction($device, move |$bus| {
// Safety: Implementers of the `SpiDevice` trait guarantee that the pointer is
// valid and dereferencable for the entire duration of the closure.
let $bus = unsafe { &mut *$bus };
async {
let result = $closure_body;
let $bus = $bus; // Ensure that the bus reference was not moved out of the closure
let _ = $bus; // Silence the "unused variable" warning from prevous line
result
}
})
};
($device:expr, |$bus:ident| async move $closure_body:expr) => {
$crate::spi::SpiDevice::transaction($device, |$bus| {
// Safety: Implementers of the `SpiDevice` trait guarantee that the pointer is
// valid and dereferencable for the entire duration of the closure.
let $bus = unsafe { &mut *$bus };
async move {
let result = $closure_body;
let $bus = $bus; // Ensure that the bus reference was not moved out of the closure
let _ = $bus; // Silence the "unused variable" warning from prevous line
result
}
})
};
($device:expr, |$bus:ident| async $closure_body:expr) => {
$crate::spi::SpiDevice::transaction($device, |$bus| {
// Safety: Implementers of the `SpiDevice` trait guarantee that the pointer is
// valid and dereferencable for the entire duration of the closure.
let $bus = unsafe { &mut *$bus };
async {
let result = $closure_body;
let $bus = $bus; // Ensure that the bus reference was not moved out of the closure
let _ = $bus; // Silence the "unused variable" warning from prevous line
result
}
})
};
}
#[doc(inline)]
pub use spi_transaction as transaction;
/// 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.
///
/// # Safety
///
/// See [`SpiDevice::transaction`] for details.
pub unsafe trait SpiDevice: ErrorType {
/// SPI Bus type for this device.
type Bus: ErrorType;
/// Perform a transaction against the device.
///
/// **NOTE:**
/// It is not recommended to use this method directly, because it requires `unsafe` code to dereference the raw pointer.
/// Instead, the [`transaction!`] macro should be used, which handles this safely inside the macro.
///
/// - 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.
///
/// On bus errors the implementation should try to deassert CS.
/// If an error occurs while deasserting CS the bus error should take priority as the return value.
///
/// # Safety
///
/// The current state of the Rust typechecker doesn't allow expressing the necessary lifetime constraints, so
/// the `f` closure receives a lifetime-less `*mut Bus` raw pointer instead.
///
/// Implementers of the `SpiDevice` trait must guarantee that the pointer is valid and dereferencable
/// for the entire duration of the closure.
async fn transaction<R, F, Fut>(&mut self, f: F) -> Result<R, Self::Error>
where
F: FnOnce(*mut Self::Bus) -> Fut,
Fut: Future<Output = Result<R, <Self::Bus as ErrorType>::Error>>;
/// Do a read within a transaction.
///
/// This is a convenience method equivalent to `device.transaction(|bus| bus.read(buf))`.
///
/// See also: [`SpiDevice::transaction`], [`SpiBusRead::read`]
async fn read<'a, Word>(&'a mut self, buf: &'a mut [Word]) -> Result<(), Self::Error>
where
Self::Bus: SpiBusRead<Word>,
Word: Copy + 'static,
{
transaction!(self, move |bus| async move { bus.read(buf).await }).await
}
/// Do a write within a transaction.
///
/// This is a convenience method equivalent to `device.transaction(|bus| bus.write(buf))`.
///
/// See also: [`SpiDevice::transaction`], [`SpiBusWrite::write`]
async fn write<'a, Word>(&'a mut self, buf: &'a [Word]) -> Result<(), Self::Error>
where
Self::Bus: SpiBusWrite<Word>,
Word: Copy + 'static,
{
transaction!(self, move |bus| async move { bus.write(buf).await }).await
}
/// Do a transfer within a transaction.
///
/// This is a convenience method equivalent to `device.transaction(|bus| bus.transfer(read, write))`.
///
/// See also: [`SpiDevice::transaction`], [`SpiBus::transfer`]
async fn transfer<'a, Word>(
&'a mut self,
read: &'a mut [Word],
write: &'a [Word],
) -> Result<(), Self::Error>
where
Self::Bus: SpiBus<Word>,
Word: Copy + 'static,
{
transaction!(
self,
move |bus| async move { bus.transfer(read, write).await }
)
.await
}
/// Do an in-place transfer within a transaction.
///
/// This is a convenience method equivalent to `device.transaction(|bus| bus.transfer_in_place(buf))`.
///
/// See also: [`SpiDevice::transaction`], [`SpiBus::transfer_in_place`]
async fn transfer_in_place<'a, Word>(
&'a mut self,
buf: &'a mut [Word],
) -> Result<(), Self::Error>
where
Self::Bus: SpiBus<Word>,
Word: Copy + 'static,
{
transaction!(
self,
move |bus| async move { bus.transfer_in_place(buf).await }
)
.await
}
}
unsafe impl<T: SpiDevice> SpiDevice for &mut T {
type Bus = T::Bus;
async fn transaction<R, F, Fut>(&mut self, f: F) -> Result<R, Self::Error>
where
F: FnOnce(*mut Self::Bus) -> Fut,
Fut: Future<Output = Result<R, <Self::Bus as ErrorType>::Error>>,
{
T::transaction(self, f).await
}
}
/// Flush support for SPI bus
pub trait SpiBusFlush: ErrorType {
/// 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.
async fn flush(&mut self) -> Result<(), Self::Error>;
}
impl<T: SpiBusFlush> SpiBusFlush for &mut T {
async fn flush(&mut self) -> Result<(), Self::Error> {
T::flush(self).await
}
}
/// Read-only SPI bus
pub trait SpiBusRead<Word: 'static + Copy = u8>: SpiBusFlush {
/// 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.
async fn read(&mut self, words: &mut [Word]) -> Result<(), Self::Error>;
}
impl<T: SpiBusRead<Word>, Word: 'static + Copy> SpiBusRead<Word> for &mut T {
async fn read(&mut self, words: &mut [Word]) -> Result<(), Self::Error> {
T::read(self, words).await
}
}
/// Write-only SPI
pub trait SpiBusWrite<Word: 'static + Copy = u8>: SpiBusFlush {
/// 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.
async fn write(&mut self, words: &[Word]) -> Result<(), Self::Error>;
}
impl<T: SpiBusWrite<Word>, Word: 'static + Copy> SpiBusWrite<Word> for &mut T {
async fn write(&mut self, words: &[Word]) -> Result<(), Self::Error> {
T::write(self, words).await
}
}
/// 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> {
/// 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.
async fn transfer<'a>(
&'a mut self,
read: &'a mut [Word],
write: &'a [Word],
) -> Result<(), Self::Error>;
/// 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.
async fn transfer_in_place<'a>(&'a mut self, words: &'a mut [Word]) -> Result<(), Self::Error>;
}
impl<T: SpiBus<Word>, Word: 'static + Copy> SpiBus<Word> for &mut T {
async fn transfer<'a>(
&'a mut self,
read: &'a mut [Word],
write: &'a [Word],
) -> Result<(), Self::Error> {
T::transfer(self, read, write).await
}
async fn transfer_in_place<'a>(&'a mut self, words: &'a mut [Word]) -> Result<(), Self::Error> {
T::transfer_in_place(self, words).await
}
}
/// 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)
}
}
unsafe impl<BUS, CS> SpiDevice for ExclusiveDevice<BUS, CS>
where
BUS: SpiBusFlush,
CS: OutputPin,
{
type Bus = BUS;
async fn transaction<R, F, Fut>(&mut self, f: F) -> Result<R, Self::Error>
where
F: FnOnce(*mut Self::Bus) -> Fut,
Fut: Future<Output = Result<R, <Self::Bus as ErrorType>::Error>>,
{
self.cs.set_low().map_err(ExclusiveDeviceError::Cs)?;
let f_res = f(&mut self.bus).await;
// On failure, it's important to still flush and deassert CS.
let flush_res = self.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)
}
}