stm32f7x7_hal/
delay.rs

1//! Delays
2
3use cast::u32;
4use cortex_m::peripheral::syst::SystClkSource;
5use cortex_m::peripheral::SYST;
6
7use crate::rcc::Clocks;
8use embedded_hal::blocking::delay::{DelayMs, DelayUs};
9
10/// System timer (SysTick) as a delay provider
11pub struct Delay {
12    clocks: Clocks,
13    syst: SYST,
14}
15
16impl Delay {
17    /// Configures the system timer (SysTick) as a delay provider
18    pub fn new(mut syst: SYST, clocks: Clocks) -> Self {
19        syst.set_clock_source(SystClkSource::External);
20
21        Delay { syst, clocks }
22    }
23
24    /// Releases the system timer (SysTick) resource
25    pub fn free(self) -> SYST {
26        self.syst
27    }
28}
29
30impl DelayMs<u32> for Delay {
31    fn delay_ms(&mut self, ms: u32) {
32        self.delay_us(ms * 1_000);
33    }
34}
35
36impl DelayMs<u16> for Delay {
37    fn delay_ms(&mut self, ms: u16) {
38        self.delay_ms(u32(ms));
39    }
40}
41
42impl DelayMs<u8> for Delay {
43    fn delay_ms(&mut self, ms: u8) {
44        self.delay_ms(u32(ms));
45    }
46}
47
48impl DelayUs<u32> for Delay {
49    fn delay_us(&mut self, us: u32) {
50        // The SysTick Reload Value register supports values between 1 and 0x00FFFFFF.
51        const MAX_RVR: u32 = 0x00FF_FFFF;
52
53        let mut total_rvr = us * (self.clocks.hclk().0 / 8_000_000);
54
55        while total_rvr != 0 {
56            let current_rvr = if total_rvr <= MAX_RVR {
57                total_rvr
58            } else {
59                MAX_RVR
60            };
61
62            self.syst.set_reload(current_rvr);
63            self.syst.clear_current();
64            self.syst.enable_counter();
65
66            // Update the tracking variable while we are waiting...
67            total_rvr -= current_rvr;
68
69            while !self.syst.has_wrapped() {}
70
71            self.syst.disable_counter();
72        }
73    }
74}
75
76impl DelayUs<u16> for Delay {
77    fn delay_us(&mut self, us: u16) {
78        self.delay_us(u32(us))
79    }
80}
81
82impl DelayUs<u8> for Delay {
83    fn delay_us(&mut self, us: u8) {
84        self.delay_us(u32(us))
85    }
86}
stm32f7x7_hal/delay.rs

stm32f7x7_hal/
delay.rs
