Merge pull request #259 from thalesfragoso/block-timer

Add BlockingTimer and features to choose tick rate

2 files changed, 74 insertions, 2 deletions

diff --git a/embassy/Cargo.toml b/embassy/Cargo.toml
index 6364f9902..87f54409a 100644
--- a/embassy/Cargo.toml
+++ b/embassy/Cargo.toml
@@ -5,7 +5,11 @@ authors = ["Dario Nieuwenhuis <[email protected]>"]
 edition = "2018"
 
 [features]
+default = ["tick-32768hz"]
 std = ["futures/std", "embassy-traits/std"]
+tick-32768hz = []
+tick-1000hz = []
+tick-1mhz = []
 
 defmt-trace = []
 defmt-debug = []
@@ -26,6 +30,7 @@ embassy-macros  = { version = "0.1.0", path = "../embassy-macros"}
 embassy-traits  = { version = "0.1.0", path = "../embassy-traits"}
 atomic-polyfill  = { version = "0.1.1" }
 critical-section = "0.2.1"
+embedded-hal = "0.2.5"
 
 # Workaround https://github.com/japaric/cast.rs/pull/27
 cast = { version = "=0.2.3", default-features = false }
diff --git a/embassy/src/time/mod.rs b/embassy/src/time/mod.rs
index 21b93d384..d50d9ef0d 100644
--- a/embassy/src/time/mod.rs
+++ b/embassy/src/time/mod.rs
@@ -10,8 +10,22 @@ pub use duration::Duration;
 pub use instant::Instant;
 pub use traits::*;
 
-// TODO allow customizing, probably via Cargo features `tick-hz-32768` or something.
-pub const TICKS_PER_SECOND: u64 = 32768;
+#[cfg(any(
+    all(feature = "tick-32768hz", feature = "tick-1000hz"),
+    all(feature = "tick-32768hz", feature = "tick-1mhz"),
+))]
+compile_error!(
+    "Disable default-features to be able to use a tick rate other than the default (32768 Hz)"
+);
+
+#[cfg(feature = "tick-1000hz")]
+pub const TICKS_PER_SECOND: u64 = 1_000;
+
+#[cfg(feature = "tick-32768hz")]
+pub const TICKS_PER_SECOND: u64 = 32_768;
+
+#[cfg(feature = "tick-1mhz")]
+pub const TICKS_PER_SECOND: u64 = 1_000_000;
 
 static mut CLOCK: Option<&'static dyn Clock> = None;
 
@@ -28,3 +42,56 @@ pub unsafe fn set_clock(clock: &'static dyn Clock) {
 pub(crate) fn now() -> u64 {
     unsafe { unwrap!(CLOCK, "No clock set").now() }
 }
+
+/// Type used for blocking delays through embedded-hal traits.
+///
+/// For this interface to work, the Executor's clock must be correctly initialized before using it.
+/// The delays are implemented in a "best-effort" way, meaning that the cpu will block for at least
+/// the amount provided, but accuracy can be affected by many factors, including interrupt usage.
+/// Make sure to use a suitable tick rate for your use case. The tick rate can be chosen through
+/// features flags of this crate.
+pub struct BlockingTimer;
+
+impl embedded_hal::blocking::delay::DelayMs<u8> for BlockingTimer {
+    fn delay_ms(&mut self, ms: u8) {
+        block_for(Duration::from_millis(ms as u64))
+    }
+}
+
+impl embedded_hal::blocking::delay::DelayMs<u16> for BlockingTimer {
+    fn delay_ms(&mut self, ms: u16) {
+        block_for(Duration::from_millis(ms as u64))
+    }
+}
+
+impl embedded_hal::blocking::delay::DelayMs<u32> for BlockingTimer {
+    fn delay_ms(&mut self, ms: u32) {
+        block_for(Duration::from_millis(ms as u64))
+    }
+}
+
+impl embedded_hal::blocking::delay::DelayUs<u8> for BlockingTimer {
+    fn delay_us(&mut self, us: u8) {
+        block_for(Duration::from_micros(us as u64))
+    }
+}
+
+impl embedded_hal::blocking::delay::DelayUs<u16> for BlockingTimer {
+    fn delay_us(&mut self, us: u16) {
+        block_for(Duration::from_micros(us as u64))
+    }
+}
+
+impl embedded_hal::blocking::delay::DelayUs<u32> for BlockingTimer {
+    fn delay_us(&mut self, us: u32) {
+        block_for(Duration::from_micros(us as u64))
+    }
+}
+
+/// Blocks the cpu for at least `duration`.
+///
+/// For this interface to work, the Executor's clock must be correctly initialized before using it.
+pub fn block_for(duration: Duration) {
+    let expires_at = Instant::now() + duration;
+    while Instant::now() < expires_at {}
+}