async: add DelayUs

.github/workflows/clippy-async.yml

@@ -0,0 +1,19 @@
+on:
+  push:
+    branches: [ staging, trying, master ]
+  pull_request:
+
+name: Clippy check
+jobs:
+  clippy_check-async:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+          override: true
+          components: clippy
+      - run: cargo clippy
+        working-directory: embedded-hal-async

.github/workflows/clippy.yml

@@ -18,5 +18,3 @@ jobs:
       - uses: actions-rs/clippy-check@v1
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
-      - run: cargo clippy
-        working-directory: embedded-hal-async

embedded-hal-async/src/delay.rs

@@ -0,0 +1,52 @@
+//! Delays
+
+use core::future::Future;
+
+/// Microsecond delay
+pub trait DelayUs {
+    /// Enumeration of errors
+    type Error: core::fmt::Debug;
+
+    /// The future returned by the `delay_us` function.
+    type DelayUsFuture<'a>: Future<Output = Result<(), Self::Error>> + 'a
+    where
+        Self: 'a;
+
+    /// Pauses execution for at minimum `us` microseconds. Pause can be longer
+    /// if the implementation requires it due to precision/timing issues.
+    fn delay_us(&mut self, us: u32) -> Self::DelayUsFuture<'_>;
+
+    /// The future returned by the `delay_ms` function.
+    type DelayMsFuture<'a>: Future<Output = Result<(), Self::Error>> + 'a
+    where
+        Self: 'a;
+
+    /// Pauses execution for at minimum `ms` milliseconds. Pause can be longer
+    /// if the implementation requires it due to precision/timing issues.
+    fn delay_ms(&mut self, ms: u32) -> Self::DelayMsFuture<'_>;
+}
+
+impl<T> DelayUs for &mut T
+where
+    T: DelayUs,
+{
+    type Error = T::Error;
+
+    type DelayUsFuture<'a>
+    where
+        Self: 'a,
+    = T::DelayUsFuture<'a>;
+
+    fn delay_us(&mut self, us: u32) -> Self::DelayUsFuture<'_> {
+        T::delay_us(self, us)
+    }
+
+    type DelayMsFuture<'a>
+    where
+        Self: 'a,
+    = T::DelayMsFuture<'a>;
+
+    fn delay_ms(&mut self, ms: u32) -> Self::DelayMsFuture<'_> {
+        T::delay_ms(self, ms)
+    }
+}

embedded-hal-async/src/lib.rs

@@ -9,3 +9,6 @@
 
 #![deny(missing_docs)]
 #![no_std]
+#![feature(generic_associated_types)]
+
+pub mod delay;