Struct Signal 

pub struct Signal<M, T>
where
    M: RawMutex,
{ /* private fields */ }

Single-slot signaling primitive for a single consumer.

This is similar to a Channel with a buffer size of 1, except “sending” to it (calling Signal::signal) when full will overwrite the previous value instead of waiting for the receiver to pop the previous value.

It is useful for sending data between tasks when the receiver only cares about the latest data, and therefore it’s fine to “lose” messages. This is often the case for “state” updates.

For more advanced use cases, you might want to use Channel instead. For multiple consumers, use Watch instead.

Signals are generally declared as statics and then borrowed as required.

use embassy_sync::signal::Signal;
use embassy_sync::blocking_mutex::raw::CriticalSectionRawMutex;

enum SomeCommand {
  On,
  Off,
}

static SOME_SIGNAL: Signal<CriticalSectionRawMutex, SomeCommand> = Signal::new();

Implementations

impl<M, T> Signal<M, T>

where M: RawMutex,

pub const fn new() -> Self

Create a new Signal.

impl<M, T> Signal<M, T>

where M: RawMutex,

pub fn signal(&self, val: T)

Mark this Signal as signaled.

pub fn reset(&self)

Remove the queued value in this Signal, if any.

pub fn poll_wait(&self, cx: &mut Context<'_>) -> Poll<T>

Poll for state changes of this Signal.

pub fn wait(&self) -> impl Future<Output = T> + '_

Future that completes when this Signal has been signaled, taking the value out of the signal.

The returned Future is cancel-safe. No value will be lost even if it isn’t polled to completion.

pub fn try_take(&self) -> Option<T>

non-blocking method to try and take the signal value.

pub fn signaled(&self) -> bool

non-blocking method to check whether this signal has been signaled. This does not clear the signal.

Trait Implementations

impl<M, T> Default for Signal<M, T>

where M: RawMutex,

fn default() -> Self

Returns the “default value” for a type.

impl<M, T> Sink<T> for Signal<M, T>

where M: RawMutex,

type Error = !

The type of value produced by the sink when an error occurs.

fn poll_ready( self: Pin<&mut Self>, _cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

Attempts to prepare the Sink to receive a value.

fn start_send(self: Pin<&mut Self>, item: T) -> Result<(), Self::Error>

Begin the process of sending a value to the sink. Each call to this function must be preceded by a successful call to poll_ready which returned Poll::Ready(Ok(())).

fn poll_flush( self: Pin<&mut Self>, _cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

Flush any remaining output from this sink.

fn poll_close( self: Pin<&mut Self>, _cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

Flush any remaining output and close this sink, if necessary.

impl<M, T> Sink<T> for &Signal<M, T>

where M: RawMutex,

type Error = !

The type of value produced by the sink when an error occurs.

fn poll_ready( self: Pin<&mut Self>, _cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

Attempts to prepare the Sink to receive a value.

fn start_send(self: Pin<&mut Self>, item: T) -> Result<(), Self::Error>

Begin the process of sending a value to the sink. Each call to this function must be preceded by a successful call to poll_ready which returned Poll::Ready(Ok(())).

fn poll_flush( self: Pin<&mut Self>, _cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

Flush any remaining output from this sink.

fn poll_close( self: Pin<&mut Self>, _cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

Flush any remaining output and close this sink, if necessary.

impl<M, T> Stream for Signal<M, T>

where M: RawMutex,

type Item = T

Values yielded by the stream.

fn poll_next( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Option<Self::Item>>

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.

impl<M, T> Stream for &Signal<M, T>

where M: RawMutex,

type Item = T

Values yielded by the stream.

fn poll_next( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Option<Self::Item>>

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.