use core::future::Future;
/// SPI transfer
pub trait AsyncTransfer {
/// Write error
type Error;
/// Write byte future for polling on completion
type TransferFuture<'t>: Future<Output=Result<(), Self::Error>>;
/// Sends bytes to the slave. Returns the bytes received from the slave
fn async_transfer<'a>(&'a mut self, data: &'a mut [u8]) -> Self::TransferFuture<'a>;
}
pub mod transfer {
use super::AsyncTransfer;
use core::future::Future;
use core::task::{Context, Poll};
use core::pin::Pin;
/// Marker trait to opt into default async transfer implementation
///
/// Implementers of `embedded-hal::spi::FullDuplex<u8>` can implement this marker trait
/// for their type. Doing so will automatically provide the default
/// implementation of [`spi::AsyncTransfer`] for the type.
///
/// [`spi::AsyncTransfer`]: ../trait.AsyncTransfer.html
pub trait Default: embedded_hal::spi::FullDuplex<u8> {}
impl<S: Default + 'static> AsyncTransfer for S {
type Error = S::Error;
type TransferFuture<'t> = DefaultTransferFuture<'t, S>;
fn async_transfer<'a>(&'a mut self, data: &'a mut [u8]) -> Self::TransferFuture<'a> {
DefaultTransferFuture {
spi: self,
data,
offset: 0,
state: State::Sending
}
}
}
enum State {
Sending,
Receiving,
}
pub struct DefaultTransferFuture<'a, S> {
spi: &'a mut S,
data: &'a mut [u8],
offset: usize,
state: State,
}
impl<'a, S: Default> Future for DefaultTransferFuture<'a, S> {
type Output = Result<(), S::Error>;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
while self.offset < self.data.len() {
match self.state {
State::Sending => {
let byte = self.data[self.offset];
match self.spi.send(byte) {
Ok(()) => {
self.state = State::Receiving;
continue;
},
Err(nb::Error::Other(e)) => {
return Poll::Ready(Err(e));
},
Err(nb::Error::WouldBlock) => {
cx.waker().wake_by_ref();
return Poll::Pending;
}
}
},
State::Receiving => {
match self.spi.read() {
Ok(byte) => {
let offset = self.offset;
self.data[offset] = byte;
self.offset += 1;
self.state = State::Sending;
continue;
},
Err(nb::Error::Other(e)) => {
return Poll::Ready(Err(e));
},
Err(nb::Error::WouldBlock) => {
cx.waker().wake_by_ref();
return Poll::Pending;
}
}
},
}
}
Poll::Ready(Ok(()))
}
}
}