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|
//! 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,
ahb_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(mut syst: SYST, ahb_frequency: u32) -> Self {
syst.set_clock_source(SystClkSource::Core);
Delay {
syst,
ahb_frequency,
}
}
/// Releases the system timer (SysTick) resource.
#[inline]
pub fn free(self) -> SYST {
self.syst
}
fn _delay_us(&mut self, us: u32) {
let ticks = (us as u64) * (self.ahb_frequency as u64) / 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();
}
}
impl DelayMs<u32> for Delay {
#[inline]
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);
}
}
// 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);
self.delay_ms(ms as u32);
}
}
impl DelayMs<u16> for Delay {
#[inline(always)]
fn delay_ms(&mut self, ms: u16) {
self.delay_ms(u32::from(ms));
}
}
impl DelayMs<u8> for Delay {
#[inline(always)]
fn delay_ms(&mut self, ms: u8) {
self.delay_ms(u32::from(ms));
}
}
impl DelayUs<u32> for Delay {
#[inline]
fn delay_us(&mut self, us: u32) {
self._delay_us(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);
self.delay_us(us as u32);
}
}
impl DelayUs<u16> for Delay {
#[inline(always)]
fn delay_us(&mut self, us: u16) {
self.delay_us(u32::from(us))
}
}
impl DelayUs<u8> for Delay {
#[inline(always)]
fn delay_us(&mut self, us: u8) {
self.delay_us(u32::from(us))
}
}
|
