1 files changed, 136 insertions, 0 deletions
diff --git a/cortex-m/src/delay.rs b/cortex-m/src/delay.rs
new file mode 100644
index 0000000..66a63bf
--- /dev/null
+++ b/cortex-m/src/delay.rs
@@ -0,0 +1,136 @@
+//! A delay driver based on SysTick.
+
+use crate::peripheral::{syst::SystClkSource, SYST};
+use embedded_hal::blocking::delay::{DelayMs, DelayUs};
+
+/// System timer (SysTick) as a delay provider.
+pub struct Delay {
+    syst: SYST,
+    frequency: u32,
+}
+
+impl Delay {
+    /// Configures the system timer (SysTick) as a delay provider.
+    ///
+    /// `ahb_frequency` is a frequency of the AHB bus in Hz.
+    #[inline]
+    pub fn new(syst: SYST, ahb_frequency: u32) -> Self {
+        Self::with_source(syst, ahb_frequency, SystClkSource::Core)
+    }
+
+    /// Configures the system timer (SysTick) as a delay provider
+    /// with a clock source.
+    ///
+    /// `frequency` is the frequency of your `clock_source` in Hz.
+    #[inline]
+    pub fn with_source(mut syst: SYST, frequency: u32, clock_source: SystClkSource) -> Self {
+        syst.set_clock_source(clock_source);
+
+        Delay { syst, frequency }
+    }
+
+    /// Releases the system timer (SysTick) resource.
+    #[inline]
+    pub fn free(self) -> SYST {
+        self.syst
+    }
+
+    /// Delay using the Cortex-M systick for a certain duration, in µs.
+    #[allow(clippy::missing_inline_in_public_items)]
+    pub fn delay_us(&mut self, us: u32) {
+        let ticks = (u64::from(us)) * (u64::from(self.frequency)) / 1_000_000;
+
+        let full_cycles = ticks >> 24;
+        if full_cycles > 0 {
+            self.syst.set_reload(0xffffff);
+            self.syst.clear_current();
+            self.syst.enable_counter();
+
+            for _ in 0..full_cycles {
+                while !self.syst.has_wrapped() {}
+            }
+        }
+
+        let ticks = (ticks & 0xffffff) as u32;
+        if ticks > 1 {
+            self.syst.set_reload(ticks - 1);
+            self.syst.clear_current();
+            self.syst.enable_counter();
+
+            while !self.syst.has_wrapped() {}
+        }
+
+        self.syst.disable_counter();
+    }
+
+    /// Delay using the Cortex-M systick for a certain duration, in ms.
+    #[inline]
+    pub fn delay_ms(&mut self, mut ms: u32) {
+        // 4294967 is the highest u32 value which you can multiply by 1000 without overflow
+        while ms > 4294967 {
+            self.delay_us(4294967000u32);
+            ms -= 4294967;
+        }
+        self.delay_us(ms * 1_000);
+    }
+}
+
+impl DelayMs<u32> for Delay {
+    #[inline]
+    fn delay_ms(&mut self, ms: u32) {
+        Delay::delay_ms(self, ms);
+    }
+}
+
+// This is a workaround to allow `delay_ms(42)` construction without specifying a type.
+impl DelayMs<i32> for Delay {
+    #[inline(always)]
+    fn delay_ms(&mut self, ms: i32) {
+        assert!(ms >= 0);
+        Delay::delay_ms(self, ms as u32);
+    }
+}
+
+impl DelayMs<u16> for Delay {
+    #[inline(always)]
+    fn delay_ms(&mut self, ms: u16) {
+        Delay::delay_ms(self, u32::from(ms));
+    }
+}
+
+impl DelayMs<u8> for Delay {
+    #[inline(always)]
+    fn delay_ms(&mut self, ms: u8) {
+        Delay::delay_ms(self, u32::from(ms));
+    }
+}
+
+impl DelayUs<u32> for Delay {
+    #[inline]
+    fn delay_us(&mut self, us: u32) {
+        Delay::delay_us(self, us);
+    }
+}
+
+// This is a workaround to allow `delay_us(42)` construction without specifying a type.
+impl DelayUs<i32> for Delay {
+    #[inline(always)]
+    fn delay_us(&mut self, us: i32) {
+        assert!(us >= 0);
+        Delay::delay_us(self, us as u32);
+    }
+}
+
+impl DelayUs<u16> for Delay {
+    #[inline(always)]
+    fn delay_us(&mut self, us: u16) {
+        Delay::delay_us(self, u32::from(us))
+    }
+}
+
+impl DelayUs<u8> for Delay {
+    #[inline(always)]
+    fn delay_us(&mut self, us: u8) {
+        Delay::delay_us(self, u32::from(us))
+    }
+}