embassy_stm32/wdg/
mod.rs

1//! Watchdog Timer (IWDG, WWDG)
2use core::marker::PhantomData;
3
4use embassy_hal_internal::PeripheralType;
5use stm32_metapac::iwdg::vals::{Key, Pr};
6
7use crate::rcc::LSI_FREQ;
8use crate::Peri;
9
10/// Independent watchdog (IWDG) driver.
11pub struct IndependentWatchdog<'d, T: Instance> {
12    wdg: PhantomData<&'d mut T>,
13}
14
15// 12-bit counter
16const MAX_RL: u16 = 0xFFF;
17
18/// Calculates maximum watchdog timeout in us (RL = 0xFFF) for a given prescaler
19const fn get_timeout_us(prescaler: u16, reload_value: u16) -> u32 {
20    1_000_000 * (reload_value + 1) as u32 / (LSI_FREQ.0 / prescaler as u32)
21}
22
23/// Calculates watchdog reload value for the given prescaler and desired timeout
24const fn reload_value(prescaler: u16, timeout_us: u32) -> u16 {
25    (timeout_us / prescaler as u32 * LSI_FREQ.0 / 1_000_000) as u16 - 1
26}
27
28impl<'d, T: Instance> IndependentWatchdog<'d, T> {
29    /// Creates an IWDG (Independent Watchdog) instance with a given timeout value in microseconds.
30    ///
31    /// [Self] has to be started with [Self::unleash()].
32    /// Once timer expires, MCU will be reset. To prevent this, timer must be reloaded by repeatedly calling [Self::pet()] within timeout interval.
33    pub fn new(_instance: Peri<'d, T>, timeout_us: u32) -> Self {
34        // Find lowest prescaler value, which makes watchdog period longer or equal to timeout.
35        // This iterates from 4 (2^2) to 256 (2^8).
36        let psc_power = unwrap!((2..=8).find(|psc_power| {
37            let psc = 2u16.pow(*psc_power);
38            timeout_us <= get_timeout_us(psc, MAX_RL)
39        }));
40
41        // Prescaler value
42        let psc = 2u16.pow(psc_power);
43
44        #[cfg(not(iwdg_v3))]
45        assert!(psc <= 256, "IWDG prescaler should be no more than 256");
46        #[cfg(iwdg_v3)] // H5, U5, WBA
47        assert!(psc <= 1024, "IWDG prescaler should be no more than 1024");
48
49        // Convert prescaler power to PR register value
50        let pr = psc_power as u8 - 2;
51
52        // Reload value
53        let rl = reload_value(psc, timeout_us);
54
55        let wdg = T::regs();
56        wdg.kr().write(|w| w.set_key(Key::ENABLE));
57        wdg.pr().write(|w| w.set_pr(Pr::from_bits(pr)));
58        wdg.rlr().write(|w| w.set_rl(rl));
59
60        trace!(
61            "Watchdog configured with {}us timeout, desired was {}us (PR={}, RL={})",
62            get_timeout_us(psc, rl),
63            timeout_us,
64            pr,
65            rl
66        );
67
68        IndependentWatchdog { wdg: PhantomData }
69    }
70
71    /// Unleash (start) the watchdog.
72    pub fn unleash(&mut self) {
73        T::regs().kr().write(|w| w.set_key(Key::START));
74    }
75
76    /// Pet (reload, refresh) the watchdog.
77    pub fn pet(&mut self) {
78        T::regs().kr().write(|w| w.set_key(Key::RESET));
79    }
80}
81
82trait SealedInstance {
83    fn regs() -> crate::pac::iwdg::Iwdg;
84}
85
86/// IWDG instance trait.
87#[allow(private_bounds)]
88pub trait Instance: SealedInstance + PeripheralType {}
89
90foreach_peripheral!(
91    (iwdg, $inst:ident) => {
92        impl SealedInstance for crate::peripherals::$inst {
93            fn regs() -> crate::pac::iwdg::Iwdg {
94                crate::pac::$inst
95            }
96        }
97
98        impl Instance for crate::peripherals::$inst {}
99    };
100);
101
102#[cfg(test)]
103mod tests {
104    use super::*;
105
106    #[test]
107    fn can_compute_timeout_us() {
108        assert_eq!(125, get_timeout_us(4, 0));
109        assert_eq!(512_000, get_timeout_us(4, MAX_RL));
110
111        assert_eq!(8_000, get_timeout_us(256, 0));
112        assert_eq!(32_768_000, get_timeout_us(256, MAX_RL));
113
114        assert_eq!(8_000_000, get_timeout_us(64, 3999));
115    }
116
117    #[test]
118    fn can_compute_reload_value() {
119        assert_eq!(0xFFF, reload_value(4, 512_000));
120        assert_eq!(0xFFF, reload_value(256, 32_768_000));
121
122        assert_eq!(3999, reload_value(64, 8_000_000));
123    }
124}
embassy_stm32/wdg/mod.rs

embassy_stm32/wdg/
mod.rs
