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stm32/rtc: use psc to compute instants

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This commit is contained in:
xoviat
2023-08-27 16:06:33 -05:00
parent 88146eb53e
commit 9f928010a8
2 changed files with 19 additions and 38 deletions
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53
embassy-stm32/src/rtc/mod.rs
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@ -47,31 +47,6 @@ struct RtcInstant {
subsecond: u16,
}
#[cfg(feature = "low-power")]
impl RtcInstant {
pub fn now() -> Self {
let tr = RTC::regs().tr().read();
let tr2 = RTC::regs().tr().read();
let ssr = RTC::regs().ssr().read().ss();
let ssr2 = RTC::regs().ssr().read().ss();
let st = bcd2_to_byte((tr.st(), tr.su()));
let st2 = bcd2_to_byte((tr2.st(), tr2.su()));
assert!(st == st2);
assert!(ssr == ssr2);
let _ = RTC::regs().dr().read();
let subsecond = ssr;
let second = st;
// trace!("rtc: instant now: st, ssr: {}, {}", st, ssr);
Self { second, subsecond }
}
}
#[cfg(feature = "low-power")]
impl core::ops::Sub for RtcInstant {
type Output = embassy_time::Duration;
@ -85,20 +60,13 @@ impl core::ops::Sub for RtcInstant {
self.second
};
// TODO: read prescaler
let psc = RTC::regs().prer().read().prediv_s() as u32;
let self_ticks = second as u32 * 256 + (255 - self.subsecond as u32);
let other_ticks = rhs.second as u32 * 256 + (255 - rhs.subsecond as u32);
let self_ticks = second as u32 * (psc + 1) + (psc - self.subsecond as u32);
let other_ticks = rhs.second as u32 * (psc + 1) + (psc - rhs.subsecond as u32);
let rtc_ticks = self_ticks - other_ticks;
// trace!(
// "rtc: instant sub: self, other, rtc ticks: {}, {}, {}",
// self_ticks,
// other_ticks,
// rtc_ticks
// );
Duration::from_ticks(((rtc_ticks * TICK_HZ as u32) / 256u32) as u64)
Duration::from_ticks(((rtc_ticks * TICK_HZ as u32) / psc) as u64)
}
}
@ -198,6 +166,19 @@ impl Rtc {
Ok(())
}
/// Return the current instant.
fn instant(&self) -> RtcInstant {
let r = RTC::regs();
let tr = r.tr().read();
let subsecond = r.ssr().read().ss();
let second = bcd2_to_byte((tr.st(), tr.su()));
// Unlock the registers
r.dr();
RtcInstant { second, subsecond }
}
/// Return the current datetime.
///
/// # Errors