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Merge pull request #160 from systec-ms/rtc_atomic_read
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RTC timestamp, was not read atomic, which can lead to wrong timestamps.
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@hannobraun
hannobraun authored Dec 8, 2021
2 parents 10eaaf3 + 5d017b6 commit aca0adf
Showing 1 changed file with 79 additions and 39 deletions.
118 changes: 79 additions & 39 deletions src/rtc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
//! For more details, see
//! [ST AN4759](https:/www.st.com%2Fresource%2Fen%2Fapplication_note%2Fdm00226326-using-the-hardware-realtime-clock-rtc-and-the-tamper-management-unit-tamp-with-stm32-microcontrollers-stmicroelectronics.pdf&usg=AOvVaw3PzvL2TfYtwS32fw-Uv37h)
use crate::pac::rtc::{dr, tr};
use crate::pac::{PWR, RCC, RTC};
use crate::rcc::{Clocks, APB1};
use core::convert::TryInto;
Expand All @@ -11,6 +12,14 @@ use rtcc::{Datelike, Hours, NaiveDate, NaiveDateTime, NaiveTime, Rtcc, Timelike}
#[derive(Debug)]
pub enum Error {
InvalidInputData,
/// The time and date are in two different registers (RTC_TR and RTC_DR),
/// so it is possible that when the time and then the date are read,
/// the date has ticked over and no longer matches the time read.
///
/// For example, it is 1970-01-01 23:59:59, so the date 1970-01-01 is read,
/// but at the moment the time register is read the RTC date time is 1970-01-02 00:00:01,
/// the result would be 1970-01-01 00:00:01, which is clearly wrong by one day.
OverTicked,
}

pub const LSE_BITS: u8 = 0b01;
Expand Down Expand Up @@ -323,34 +332,23 @@ impl Rtcc for Rtc {
}

fn get_seconds(&mut self) -> Result<u8, Self::Error> {
let tr = self.regs.tr.read();
let seconds = bcd2_decode(tr.st().bits(), tr.su().bits());
Ok(seconds as u8)
decode_seconds(&self.regs.tr.read())
}

fn get_minutes(&mut self) -> Result<u8, Self::Error> {
let tr = self.regs.tr.read();
let minutes = bcd2_decode(tr.mnt().bits(), tr.mnu().bits());
Ok(minutes as u8)
decode_minutes(&self.regs.tr.read())
}

fn get_hours(&mut self) -> Result<Hours, Self::Error> {
let tr = self.regs.tr.read();
let hours = bcd2_decode(tr.ht().bits(), tr.hu().bits());
if self.is_24h_fmt() {
return Ok(Hours::H24(hours as u8));
}
if !tr.pm().bit() {
return Ok(Hours::AM(hours as u8));
}
Ok(Hours::PM(hours as u8))
decode_hours(&self.regs.tr.read(), self.is_24h_fmt())
}

fn get_time(&mut self) -> Result<NaiveTime, Self::Error> {
self.set_24h_fmt();
let seconds = self.get_seconds().unwrap();
let minutes = self.get_minutes().unwrap();
let hours = hours_to_u8(self.get_hours()?)?;
let tr = self.regs.tr.read();
let seconds = decode_seconds(&tr).unwrap();
let minutes = decode_minutes(&tr).unwrap();
let hours = hours_to_u8(decode_hours(&tr, self.is_24h_fmt())?)?;

Ok(NaiveTime::from_hms(
hours.into(),
Expand All @@ -366,43 +364,42 @@ impl Rtcc for Rtc {
}

fn get_day(&mut self) -> Result<u8, Self::Error> {
let dr = self.regs.dr.read();
let day = bcd2_decode(dr.dt().bits(), dr.du().bits());
Ok(day as u8)
decode_day(&self.regs.dr.read())
}

fn get_month(&mut self) -> Result<u8, Self::Error> {
let dr = self.regs.dr.read();
let mt: u8 = if dr.mt().bit() { 1 } else { 0 };
let month = bcd2_decode(mt, dr.mu().bits());
Ok(month as u8)
decode_month(&self.regs.dr.read())
}

fn get_year(&mut self) -> Result<u16, Self::Error> {
let dr = self.regs.dr.read();
let year = bcd2_decode(dr.yt().bits(), dr.yu().bits()) + 1970; // 1970-01-01 is the epoch begin.
Ok(year as u16)
decode_year(&self.regs.dr.read())
}

fn get_date(&mut self) -> Result<NaiveDate, Self::Error> {
let day = self.get_day().unwrap();
let month = self.get_month().unwrap();
let year = self.get_year().unwrap();
let dr = self.regs.dr.read();
let day = decode_day(&dr).unwrap();
let month = decode_month(&dr).unwrap();
let year = decode_year(&dr).unwrap();

Ok(NaiveDate::from_ymd(year.into(), month.into(), day.into()))
}

fn get_datetime(&mut self) -> Result<NaiveDateTime, Self::Error> {
self.set_24h_fmt();
// If the time register is read, the upper bits are frozen until the date is read.
// Thus, read the time first, then the date.
let seconds = self.get_seconds().unwrap();
let minutes = self.get_minutes().unwrap();
let hours = hours_to_u8(self.get_hours()?)?;
let dr = self.regs.dr.read();
let tr = self.regs.tr.read();

// Check if the date has changed in the meantime, if so return an error. This guarantees a valid timestamp.
if dr.bits() != self.regs.dr.read().bits() {
return Err(Self::Error::OverTicked);
}

let day = self.get_day().unwrap();
let month = self.get_month().unwrap();
let year = self.get_year().unwrap();
let seconds = decode_seconds(&tr).unwrap();
let minutes = decode_minutes(&tr).unwrap();
let hours = hours_to_u8(decode_hours(&tr, self.is_24h_fmt())?)?;
let day = decode_day(&dr).unwrap();
let month = decode_month(&dr).unwrap();
let year = decode_year(&dr).unwrap();

Ok(
NaiveDate::from_ymd(year.into(), month.into(), day.into()).and_hms(
Expand Down Expand Up @@ -471,3 +468,46 @@ fn unlock(apb1: &mut APB1, pwr: &mut PWR) {
.set_bit()
});
}

#[inline(always)]
fn decode_seconds(tr: &tr::R) -> Result<u8, Error> {
let seconds = bcd2_decode(tr.st().bits(), tr.su().bits());
Ok(seconds as u8)
}

#[inline(always)]
fn decode_minutes(tr: &tr::R) -> Result<u8, Error> {
let minutes = bcd2_decode(tr.mnt().bits(), tr.mnu().bits());
Ok(minutes as u8)
}

#[inline(always)]
fn decode_hours(tr: &tr::R, is_24h_fmt: bool) -> Result<Hours, Error> {
let hours = bcd2_decode(tr.ht().bits(), tr.hu().bits());
if is_24h_fmt {
return Ok(Hours::H24(hours as u8));
}
if !tr.pm().bit() {
return Ok(Hours::AM(hours as u8));
}
Ok(Hours::PM(hours as u8))
}

#[inline(always)]
fn decode_day(dr: &dr::R) -> Result<u8, Error> {
let day = bcd2_decode(dr.dt().bits(), dr.du().bits());
Ok(day as u8)
}

#[inline(always)]
fn decode_month(dr: &dr::R) -> Result<u8, Error> {
let mt: u8 = if dr.mt().bit() { 1 } else { 0 };
let month = bcd2_decode(mt, dr.mu().bits());
Ok(month as u8)
}

#[inline(always)]
fn decode_year(dr: &dr::R) -> Result<u16, Error> {
let year = bcd2_decode(dr.yt().bits(), dr.yu().bits()) + 1970; // 1970-01-01 is the epoch begin.
Ok(year as u16)
}

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