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stm32: Fix watchdog timeout computation

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This commit is contained in:
Rasmus Melchior Jacobsen 2023-05-22 14:22:27 +02:00
parent ab7d129e15
commit e9121cba2c
1 changed files with 36 additions and 4 deletions
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40
embassy-stm32/src/wdg/mod.rs
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@ -13,13 +13,13 @@ pub struct IndependentWatchdog<'d, T: Instance> {
const MAX_RL: u16 = 0xFFF;
/// Calculates maximum watchdog timeout in us (RL = 0xFFF) for a given prescaler
const fn max_timeout(prescaler: u16) -> u32 {
1_000_000 * MAX_RL as u32 / (LSI_FREQ.0 / prescaler as u32)
const fn get_timeout_us(prescaler: u16, reload_value: u16) -> u32 {
1_000_000 * (reload_value + 1) as u32 / (LSI_FREQ.0 / prescaler as u32)
}
/// Calculates watchdog reload value for the given prescaler and desired timeout
const fn reload_value(prescaler: u16, timeout_us: u32) -> u16 {
(timeout_us / prescaler as u32 * LSI_FREQ.0 / 1_000_000) as u16
(timeout_us / prescaler as u32 * LSI_FREQ.0 / 1_000_000) as u16 - 1
}
impl<'d, T: Instance> IndependentWatchdog<'d, T> {
@ -34,7 +34,7 @@ impl<'d, T: Instance> IndependentWatchdog<'d, T> {
// This iterates from 4 (2^2) to 256 (2^8).
let psc_power = unwrap!((2..=8).find(|psc_power| {
let psc = 2u16.pow(*psc_power);
timeout_us <= max_timeout(psc)
timeout_us <= get_timeout_us(psc, MAX_RL)
}));
// Prescaler value
@ -54,6 +54,14 @@ impl<'d, T: Instance> IndependentWatchdog<'d, T> {
wdg.rlr().write(|w| w.set_rl(rl));
}
trace!(
"Watchdog configured with {}us timeout, desired was {}us (PR={}, RL={})",
get_timeout_us(psc, rl),
timeout_us,
pr,
rl
);
IndependentWatchdog {
wdg: PhantomData::default(),
}
@ -87,3 +95,27 @@ foreach_peripheral!(
impl Instance for crate::peripherals::$inst {}
};
);
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn can_compute_timeout_us() {
assert_eq!(125, get_timeout_us(4, 0));
assert_eq!(512_000, get_timeout_us(4, MAX_RL));
assert_eq!(8_000, get_timeout_us(256, 0));
assert_eq!(32768_000, get_timeout_us(256, MAX_RL));
assert_eq!(8000_000, get_timeout_us(64, 3999));
}
#[test]
fn can_compute_reload_value() {
assert_eq!(0xFFF, reload_value(4, 512_000));
assert_eq!(0xFFF, reload_value(256, 32768_000));
assert_eq!(3999, reload_value(64, 8000_000));
}
}