Merge #310

310: impl `Countdown` r=richardeoin a=andrewgazelka

Implements a polling version of delay (`CountDown`) in accordance to `embedded_hal`

Co-authored-by: Andrew Gazelka <andrew.gazelka@gmail.com>

Author: bors[bot]

.github/bors.toml

@@ -2,14 +2,14 @@ block_labels = ["wip"]
 delete_merged_branches = true
 status = [
     "Rustfmt",
-    "ci (1.56.1, stm32h743)",
-    "ci (1.56.1, stm32h753)",
-    "ci (1.56.1, stm32h743v)",
-    "ci (1.56.1, stm32h753v)",
-    "ci (1.56.1, stm32h747cm7)",
-    "ci (1.56.1, stm32h7b3)",
-    "ci (1.56.1, stm32h7b0)",
-    "ci (1.56.1, stm32h735)",
+    "ci (1.57.0, stm32h743)",
+    "ci (1.57.0, stm32h753)",
+    "ci (1.57.0, stm32h743v)",
+    "ci (1.57.0, stm32h753v)",
+    "ci (1.57.0, stm32h747cm7)",
+    "ci (1.57.0, stm32h7b3)",
+    "ci (1.57.0, stm32h7b0)",
+    "ci (1.57.0, stm32h735)",
     "ci (stable, stm32h743)",
     "ci (stable, stm32h753)",
     "ci (stable, stm32h743v)",

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       matrix:                   # All permutations of {rust, mcu}
         rust:
-          - 1.56.1  # MSRV
+          - 1.57.0  # MSRV
           - stable
         mcu:
           - stm32h743

Cargo.toml

@@ -25,6 +25,7 @@ features = ["stm32h743v", "rt", "xspi", "sdmmc", "fmc", "usb_hs", "rtc", "ethern
 targets = ["thumbv7em-none-eabihf"]
 
 [dependencies]
+fugit = "0.3.3"
 embedded-hal = "0.2.6"
 embedded-dma = "0.1.2"
 cortex-m = "^0.7.4"

README.md

@@ -7,7 +7,7 @@ stm32h7xx-hal
 [![Bors enabled](https://bors.tech/images/badge_small.svg)](https://app.bors.tech/repositories/12691)
 [![CI](https://github.com/stm32-rs/stm32h7xx-hal/workflows/Continuous%20integration/badge.svg)](https://github.com/stm32-rs/stm32h7xx-hal/actions)
 [![Crates.io](https://img.shields.io/crates/v/stm32h7xx-hal.svg)](https://crates.io/crates/stm32h7xx-hal)
-![Minimum rustc version](https://img.shields.io/badge/rustc-1.56.1+-yellow.svg)
+![Minimum rustc version](https://img.shields.io/badge/rustc-1.57.0+-yellow.svg)
 
 [_stm32h7xx-hal_](https://github.com/stm32-rs/stm32h7xx-hal) contains
 a hardware abstraction layer on top of the peripheral access API for
@@ -111,7 +111,7 @@ programming interfaces are only available on the high density connectors.
 Minimum supported Rust version
 ------------------------------
 
-The Minimum Supported Rust Version (MSRV) at the moment is **1.56.1**. Older
+The Minimum Supported Rust Version (MSRV) at the moment is **1.57.0**. Older
 versions **may** compile, especially when some features are not used
 in your application.
 

src/delay.rs

@@ -37,14 +37,15 @@
 use cast::u32;
 use cortex_m::peripheral::syst::SystClkSource;
 use cortex_m::peripheral::SYST;
-
-use crate::nb::block;
-use crate::rcc::CoreClocks;
-use crate::time::{Hertz, U32Ext};
 use embedded_hal::{
     blocking::delay::{DelayMs, DelayUs},
     timer::CountDown,
 };
+use void::Void;
+
+use crate::nb::block;
+use crate::rcc::CoreClocks;
+use crate::time::{Hertz, U32Ext};
 
 pub trait DelayExt {
     fn delay(self, clocks: CoreClocks) -> Delay;
@@ -62,6 +63,88 @@ pub struct Delay {
     syst: SYST,
 }
 
+/// Implements [CountDown](embedded_hal::timer::CountDown) for the System timer (SysTick).
+pub struct Countdown<'a> {
+    clocks: CoreClocks,
+    syst: &'a mut SYST,
+    total_rvr: u64,
+    finished: bool,
+}
+
+impl<'a> Countdown<'a> {
+    /// Create a new [CountDown] measured in microseconds.
+    pub fn new(syst: &'a mut SYST, clocks: CoreClocks) -> Self {
+        Self {
+            syst,
+            clocks,
+            total_rvr: 0,
+            finished: true,
+        }
+    }
+
+    /// start a wait cycle and sets finished to true if [CountdownUs] is done waiting.
+    fn start_wait(&mut self) {
+        // The SysTick Reload Value register supports values between 1 and 0x00FFFFFF.
+        const MAX_RVR: u32 = 0x00FF_FFFF;
+
+        if self.total_rvr != 0 {
+            self.finished = false;
+            let current_rvr = if self.total_rvr <= MAX_RVR.into() {
+                self.total_rvr as u32
+            } else {
+                MAX_RVR
+            };
+
+            self.syst.set_reload(current_rvr);
+            self.syst.clear_current();
+            self.syst.enable_counter();
+
+            self.total_rvr -= current_rvr as u64;
+        } else {
+            self.finished = true;
+        }
+    }
+}
+
+impl<'a> CountDown for Countdown<'a> {
+    type Time = fugit::MicrosDurationU32;
+
+    fn start<T>(&mut self, count: T)
+    where
+        T: Into<Self::Time>,
+    {
+        let us = count.into().ticks();
+
+        // With c_ck up to 480e6, we need u64 for delays > 8.9s
+
+        self.total_rvr = if cfg!(not(feature = "revision_v")) {
+            // See errata ES0392 §2.2.3. Revision Y does not have the /8 divider
+            u64::from(us) * u64::from(self.clocks.c_ck().0 / 1_000_000)
+        } else if cfg!(feature = "cm4") {
+            // CM4 dervived from HCLK
+            u64::from(us) * u64::from(self.clocks.hclk().0 / 8_000_000)
+        } else {
+            // Normally divide by 8
+            u64::from(us) * u64::from(self.clocks.c_ck().0 / 8_000_000)
+        };
+
+        self.start_wait();
+    }
+
+    fn wait(&mut self) -> nb::Result<(), Void> {
+        if self.finished {
+            return Ok(());
+        }
+
+        if self.syst.has_wrapped() {
+            self.syst.disable_counter();
+            self.start_wait();
+        }
+
+        Err(nb::Error::WouldBlock)
+    }
+}
+
 impl Delay {
     /// Configures the system timer (SysTick) as a delay provider
     pub fn new(mut syst: SYST, clocks: CoreClocks) -> Self {
@@ -105,7 +188,7 @@ impl DelayUs<u32> for Delay {
             // See errata ES0392 §2.2.3. Revision Y does not have the /8 divider
             u64::from(us) * u64::from(self.clocks.c_ck().0 / 1_000_000)
         } else if cfg!(feature = "cm4") {
-            // CM4 dervived from HCLK
+            // CM4 derived from HCLK
             u64::from(us) * u64::from(self.clocks.hclk().0 / 8_000_000)
         } else {
             // Normally divide by 8