Allow setting RTC time (#1883)

* Initial WIP RTC set implementation

* Deprecate get_time_raw and add docs + some cleanup

* Update rtc time example

* Format

* Update changelog

* Add some comments linking the PR

* Small compilation fixes

* C6 and H2 fixes

* Remove parantheses from if statement lol

* Remove accidental changelog change

* Implement boot time wrapping to avoid overflows

* Remove unused get_rtc_time_ms and get_rtc_time_us functions

* Make get_rtc_time_us public and re-add get_rtc_time_ms as public

* Update changelog

* Remove get_time_raw and replace with public get_rtc_time_raw

* Changelog reordering

* Function renaming

* Use fugit and update changelog

* Small typo fix

* Fix changelog addition from merging

* Use chrono for current_time and set_current_time

* Fix changelog

* Update example

* Fix merge errors

* Rename `time::current_time` to `time::uptime`

* Revert "Rename `time::current_time` to `time::uptime`"

This reverts commit fe8446899747c88d5b9f945f319e1133b90773ee.

* Format

* Add info to migration guide

* Fix compilation for esp32c2

* Remove information about setting RTC time from migration guide since it isn't really relevant

---------

Co-authored-by: naturecodevoid <44983869+naturecodevoid@users.noreply.github.com>

esp-hal/CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added sleep and wakeup support for esp32c2 (#1922)
 - `Input`, `Output`, `OutputOpenDrain` and `Flex` now implement `Peripheral`. (#2094)
 - Previously unavailable memory is available via `.dram2_uninit` section (#2079)
+- Added `Rtc::set_current_time` to allow setting RTC time, and `Rtc::current_time` to getting RTC time while taking into account boot time (#1883)
 
 ### Changed
 
@@ -31,6 +32,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - To avoid confusion with the `Rtc::current_time` wall clock time APIs, we've renamed `esp_hal::time::current_time` to `esp_hal::time::now`. (#2091)
 - Renamed `touch::Continous` to `touch::Continuous`. (#2094)
 - The (previously undocumented) `ErasedPin` enum has been replaced with the `ErasedPin` struct. (#2094)
+- Renamed and merged `Rtc::get_time_us` and `Rtc::get_time_ms` into `Rtc::time_since_boot` (#1883)
 
 ### Fixed
 
@@ -48,6 +50,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Removed `Peripherals::take`. Use `esp_hal::init` to obtain `Peripherals` (#1999)
 - Removed `AnyInputOnlyPin` in favour of `AnyPin`. (#2071)
 - Removed the following functions from `GpioPin`: `is_high`, `is_low`, `set_high`, `set_low`, `set_state`, `is_set_high`, `is_set_low`, `toggle`. (#2094)
+- Removed `Rtc::get_time_raw` (#1883)
 
 ## [0.20.1] - 2024-08-30
 

esp-hal/Cargo.toml

@@ -19,6 +19,7 @@ bitflags                 = "2.6.0"
 bytemuck                 = "1.17.1"
 bitfield                 = "0.16.1"
 cfg-if                   = "1.0.0"
+chrono                   = { version = "0.4.38", default-features = false }
 critical-section         = "1.1.3"
 defmt                    = { version = "0.3.8", optional = true }
 delegate                 = "0.12.0"

esp-hal/MIGRATING-0.20.md

@@ -80,3 +80,13 @@ let dma_rx_buf = DmaRxBuf::new(rx_descriptors, rx_buffer).unwrap();
     .map_err(|e| e.0)
     .unwrap();
 ```
+
+## RTC Wall Clock APIs
+
+Instead of the `get_time_ms`, `get_time_us`, and `get_time_raw` functions, the `Rtc` struct now provides the `current_time` function, using `chrono`'s `NaiveDateTime` struct.
+
+```diff
+let rtc = Rtc::new(peripherals.LPWR);
+- let current_time_ms = rtc.get_time_ms();
++ let current_time_ms = rtc.current_time().and_utc().timestamp_millis(); // assuming UTC
+```

esp-hal/src/rtc_cntl/mod.rs

@@ -66,6 +66,7 @@
 //! }
 //! ```
 
+use chrono::{DateTime, NaiveDateTime};
 #[cfg(not(any(esp32c6, esp32h2)))]
 use fugit::HertzU32;
 use fugit::MicrosDurationU64;
@@ -78,7 +79,7 @@ use crate::efuse::Efuse;
 #[cfg(not(any(esp32c6, esp32h2)))]
 use crate::peripherals::{LPWR, TIMG0};
 #[cfg(any(esp32c6, esp32h2))]
-use crate::peripherals::{LP_TIMER, LP_WDT};
+use crate::peripherals::{LP_AON, LP_TIMER, LP_WDT};
 #[cfg(any(esp32, esp32s3, esp32c3, esp32c6, esp32c2))]
 use crate::rtc_cntl::sleep::{RtcSleepConfig, WakeSource, WakeTriggers};
 use crate::{
@@ -214,8 +215,8 @@ impl<'d> Rtc<'d> {
         RtcClock::estimate_xtal_frequency()
     }
 
-    /// Read the current value of the rtc time registers.
-    pub fn get_time_raw(&self) -> u64 {
+    /// Get the time since boot in the raw register units.
+    fn time_since_boot_raw(&self) -> u64 {
         #[cfg(not(any(esp32c6, esp32h2)))]
         let rtc_cntl = unsafe { &*LPWR::ptr() };
         #[cfg(any(esp32c6, esp32h2))]
@@ -253,14 +254,112 @@ impl<'d> Rtc<'d> {
         ((h as u64) << 32) | (l as u64)
     }
 
-    /// Read the current value of the rtc time registers in microseconds.
-    pub fn get_time_us(&self) -> u64 {
-        self.get_time_raw() * 1_000_000 / RtcClock::get_slow_freq().frequency().to_Hz() as u64
+    /// Get the time since boot.
+    pub fn time_since_boot(&self) -> MicrosDurationU64 {
+        MicrosDurationU64::micros(
+            self.time_since_boot_raw() * 1_000_000
+                / RtcClock::get_slow_freq().frequency().to_Hz() as u64,
+        )
     }
 
-    /// Read the current value of the rtc time registers in milliseconds.
-    pub fn get_time_ms(&self) -> u64 {
-        self.get_time_raw() * 1_000 / RtcClock::get_slow_freq().frequency().to_Hz() as u64
+    /// Read the current value of the boot time registers in microseconds.
+    fn boot_time_us(&self) -> u64 {
+        // For more info on about how RTC setting works and what it has to do with boot time, see https://github.com/esp-rs/esp-hal/pull/1883
+
+        // In terms of registers, STORE2 and STORE3 are used on all current chips
+        // (esp32, esp32p4, esp32h2, esp32c2, esp32c3, esp32c5, esp32c6, esp32c61,
+        // esp32s2, esp32s3)
+
+        // In terms of peripherals:
+
+        // - LPWR is used on the following chips: esp32, esp32p4, esp32c2, esp32c3,
+        //   esp32s2, esp32s3
+
+        // - LP_AON is used on the following chips: esp32c5, esp32c6, esp32c61, esp32h2
+
+        // For registers and peripherals used in esp-idf, see https://github.com/search?q=repo%3Aespressif%2Fesp-idf+RTC_BOOT_TIME_LOW_REG+RTC_BOOT_TIME_HIGH_REG+path%3A**%2Frtc.h&type=code
+
+        #[cfg(not(any(esp32c6, esp32h2)))]
+        let rtc_cntl = unsafe { &*LPWR::ptr() };
+        #[cfg(any(esp32c6, esp32h2))]
+        let rtc_cntl = unsafe { &*LP_AON::ptr() };
+
+        let (l, h) = (rtc_cntl.store2(), rtc_cntl.store3());
+
+        let l = l.read().bits() as u64;
+        let h = h.read().bits() as u64;
+
+        // https://github.com/espressif/esp-idf/blob/23e4823f17a8349b5e03536ff7653e3e584c9351/components/newlib/port/esp_time_impl.c#L115
+        l + (h << 32)
+    }
+
+    /// Set the current value of the boot time registers in microseconds.
+    fn set_boot_time_us(&self, boot_time_us: u64) {
+        // Please see `boot_time_us` for documentation on registers and peripherals
+        // used for certain SOCs.
+
+        #[cfg(not(any(esp32c6, esp32h2)))]
+        let rtc_cntl = unsafe { &*LPWR::ptr() };
+        #[cfg(any(esp32c6, esp32h2))]
+        let rtc_cntl = unsafe { &*LP_AON::ptr() };
+
+        let (l, h) = (rtc_cntl.store2(), rtc_cntl.store3());
+
+        // https://github.com/espressif/esp-idf/blob/23e4823f17a8349b5e03536ff7653e3e584c9351/components/newlib/port/esp_time_impl.c#L102-L103
+        l.write(|w| unsafe { w.bits((boot_time_us & 0xffffffff) as u32) });
+        h.write(|w| unsafe { w.bits((boot_time_us >> 32) as u32) });
+    }
+
+    /// Get the current time.
+    pub fn current_time(&self) -> NaiveDateTime {
+        // Current time is boot time + time since boot
+
+        let rtc_time_us = self.time_since_boot().to_micros();
+        let boot_time_us = self.boot_time_us();
+        let wrapped_boot_time_us = u64::MAX - boot_time_us;
+
+        // We can detect if we wrapped the boot time by checking if rtc time is greater
+        // than the amount of time we would've wrapped.
+        let current_time_us = if rtc_time_us > wrapped_boot_time_us {
+            // We also just checked that this won't overflow
+            rtc_time_us - wrapped_boot_time_us
+        } else {
+            boot_time_us + rtc_time_us
+        };
+
+        DateTime::from_timestamp_micros(current_time_us as i64)
+            .unwrap()
+            .naive_utc()
+    }
+
+    /// Set the current time.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `current_time` is before the Unix epoch (meaning the
+    /// underlying timestamp is negative).
+    pub fn set_current_time(&self, current_time: NaiveDateTime) {
+        let current_time_us: u64 = current_time
+            .and_utc()
+            .timestamp_micros()
+            .try_into()
+            .expect("current_time is negative");
+
+        // Current time is boot time + time since boot (rtc time)
+        // So boot time = current time - time since boot (rtc time)
+
+        let rtc_time_us = self.time_since_boot().to_micros();
+        if current_time_us < rtc_time_us {
+            // An overflow would happen if we subtracted rtc_time_us from current_time_us.
+            // To work around this, we can wrap around u64::MAX by subtracting the
+            // difference between the current time and the time since boot.
+            // Subtracting time since boot and adding current new time is equivalent and
+            // avoids overflow. We just checked that rtc_time_us is less than time_us
+            // so this won't overflow.
+            self.set_boot_time_us(u64::MAX - rtc_time_us + current_time_us)
+        } else {
+            self.set_boot_time_us(current_time_us - rtc_time_us)
+        }
     }
 
     /// Enter deep sleep and wake with the provided `wake_sources`.

esp-hal/src/rtc_cntl/sleep/esp32.rs

@@ -82,7 +82,7 @@ impl WakeSource for TimerWakeupSource {
         let clock_hz = clock_freq.frequency().to_Hz() as u64;
         let ticks = self.duration.as_micros() as u64 * clock_hz / 1_000_000u64;
         // "alarm" time in slow rtc ticks
-        let now = rtc.get_time_raw();
+        let now = rtc.time_since_boot_raw();
         let time_in_ticks = now + ticks;
         unsafe {
             rtc_cntl

esp-hal/src/rtc_cntl/sleep/esp32c2.rs

@@ -136,7 +136,7 @@ impl WakeSource for TimerWakeupSource {
         let clock_hz = clock_freq.frequency().to_Hz() as u64;
         let ticks = self.duration.as_micros() as u64 * clock_hz / 1_000_000u64;
         // "alarm" time in slow rtc ticks
-        let now = rtc.get_time_raw();
+        let now = rtc.time_since_boot_raw();
         let time_in_ticks = now + ticks;
         unsafe {
             rtc_cntl

esp-hal/src/rtc_cntl/sleep/esp32c3.rs

@@ -136,7 +136,7 @@ impl WakeSource for TimerWakeupSource {
         let clock_hz = clock_freq.frequency().to_Hz() as u64;
         let ticks = self.duration.as_micros() as u64 * clock_hz / 1_000_000u64;
         // "alarm" time in slow rtc ticks
-        let now = rtc.get_time_raw();
+        let now = rtc.time_since_boot_raw();
         let time_in_ticks = now + ticks;
         unsafe {
             rtc_cntl

esp-hal/src/rtc_cntl/sleep/esp32c6.rs

@@ -46,7 +46,7 @@ impl WakeSource for TimerWakeupSource {
         let clock_hz = clock_freq.frequency().to_Hz() as u64;
         let ticks = self.duration.as_micros() as u64 * clock_hz / 1_000_000u64;
         // "alarm" time in slow rtc ticks
-        let now = rtc.get_time_raw();
+        let now = rtc.time_since_boot_raw();
         let time_in_ticks = now + ticks;
         unsafe {
             lp_timer.tar0_high().write(|w| {

esp-hal/src/rtc_cntl/sleep/esp32s3.rs

@@ -122,7 +122,7 @@ impl WakeSource for TimerWakeupSource {
         let clock_hz = clock_freq.frequency().to_Hz() as u64;
         let ticks = self.duration.as_micros() as u64 * clock_hz / 1_000_000u64;
         // "alarm" time in slow rtc ticks
-        let now = rtc.get_time_raw();
+        let now = rtc.time_since_boot_raw();
         let time_in_ticks = now + ticks;
         unsafe {
             rtc_cntl

examples/src/bin/rtc_time.rs

@@ -5,6 +5,8 @@
 #![no_std]
 #![no_main]
 
+use core::time::Duration;
+
 use esp_backtrace as _;
 use esp_hal::{delay::Delay, prelude::*, rtc_cntl::Rtc};
 
@@ -16,7 +18,18 @@ fn main() -> ! {
     let delay = Delay::new();
 
     loop {
-        esp_println::println!("rtc time in milliseconds is {}", rtc.get_time_ms());
+        esp_println::println!(
+            "rtc time in milliseconds is {}",
+            rtc.current_time().and_utc().timestamp_millis()
+        );
         delay.delay_millis(1000);
+
+        // Set the time to half a second in the past
+        let new_time = rtc.current_time() - Duration::from_millis(500);
+        esp_println::println!(
+            "setting rtc time to {} milliseconds",
+            new_time.and_utc().timestamp_millis()
+        );
+        rtc.set_current_time(new_time);
     }
 }