tm4c_hal/
delay.rs

1//! Code for busy-waiting
2
3use crate::{sysctl::Clocks, time::Hertz};
4use cortex_m::peripheral::{syst::SystClkSource, SYST};
5use embedded_hal::blocking::delay::{DelayMs, DelayUs};
6
7/// System timer (SysTick) as a delay provider
8pub struct Delay {
9    sysclk: Hertz,
10    syst: SYST,
11}
12
13impl Delay {
14    /// Configures the system timer (SysTick) as a delay provider
15    pub fn new(mut syst: SYST, clocks: &Clocks) -> Self {
16        syst.set_clock_source(SystClkSource::Core);
17
18        Delay {
19            syst,
20            sysclk: clocks.sysclk,
21        }
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(cast::u32(ms));
39    }
40}
41
42impl DelayMs<u8> for Delay {
43    fn delay_ms(&mut self, ms: u8) {
44        self.delay_ms(cast::u32(ms));
45    }
46}
47
48impl DelayUs<u32> for Delay {
49    fn delay_us(&mut self, us: u32) {
50        // Tricky to get this to not overflow
51        let mut rvr = us * (self.sysclk.0 / 1_000_000);
52        rvr += (us * ((self.sysclk.0 % 1_000_000) / 1_000)) / 1_000;
53        rvr += (us * (self.sysclk.0 % 1_000)) / 1_000_000;
54
55        while rvr >= 1 << 24 {
56            self.syst.set_reload((1 << 24) - 1);
57            self.syst.clear_current();
58            self.syst.enable_counter();
59            while !self.syst.has_wrapped() {}
60            self.syst.disable_counter();
61            rvr -= 1 << 24;
62        }
63
64        assert!(rvr < (1 << 24));
65        self.syst.set_reload(rvr);
66        self.syst.clear_current();
67        self.syst.enable_counter();
68        while !self.syst.has_wrapped() {}
69        self.syst.disable_counter();
70    }
71}
72
73impl DelayUs<u16> for Delay {
74    fn delay_us(&mut self, us: u16) {
75        self.delay_us(cast::u32(us))
76    }
77}
78
79impl DelayUs<u8> for Delay {
80    fn delay_us(&mut self, us: u8) {
81        self.delay_us(cast::u32(us))
82    }
83}
tm4c_hal/delay.rs

tm4c_hal/
delay.rs
