From a886e97a33690cf9724dedd272d3073a577f9fa4 Mon Sep 17 00:00:00 2001
From: xoviat <xoviat@users.noreply.github.com>
Date: Thu, 18 Dec 2025 09:13:05 -0600
Subject: stm32: use datemath to resume time

---
 embassy-stm32/src/rtc/mod.rs | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

(limited to 'embassy-stm32/src/rtc/mod.rs')

diff --git a/embassy-stm32/src/rtc/mod.rs b/embassy-stm32/src/rtc/mod.rs
index e88bd7ab2..94ba13ae1 100644
--- a/embassy-stm32/src/rtc/mod.rs
+++ b/embassy-stm32/src/rtc/mod.rs
@@ -5,7 +5,7 @@ mod datetime;
 mod low_power;
 
 #[cfg(feature = "low-power")]
-use core::cell::{Cell, RefCell, RefMut};
+use core::cell::{RefCell, RefMut};
 #[cfg(feature = "low-power")]
 use core::ops;
 
@@ -163,7 +163,7 @@ impl<'a> ops::DerefMut for RtcBorrow<'a> {
 /// RTC driver.
 pub struct Rtc {
     #[cfg(feature = "low-power")]
-    stop_time: Mutex<CriticalSectionRawMutex, Cell<Option<low_power::RtcInstant>>>,
+    epoch: chrono::DateTime<chrono::Utc>,
     _private: (),
 }
 
@@ -225,7 +225,7 @@ impl Rtc {
 
         let mut this = Self {
             #[cfg(feature = "low-power")]
-            stop_time: Mutex::const_new(CriticalSectionRawMutex::new(), Cell::new(None)),
+            epoch: chrono::DateTime::from_timestamp_secs(0).unwrap(),
             _private: (),
         };
 
@@ -243,7 +243,10 @@ impl Rtc {
         }
 
         #[cfg(feature = "low-power")]
-        this.enable_wakeup_line();
+        {
+            this.enable_wakeup_line();
+            this.epoch = this.calc_epoch();
+        }
 
         this
     }
@@ -293,6 +296,11 @@ impl Rtc {
             });
         });
 
+        #[cfg(feature = "low-power")]
+        {
+            self.epoch = self.calc_epoch();
+        }
+
         Ok(())
     }
 
-- 
cgit