RP: Add save/restore to Rtc. Example use.

embassy-rp/src/rtc/mod.rs

@@ -41,6 +41,36 @@ impl<'d, T: Instance> Rtc<'d, T> {
         });
     }
 
+    /// Set the time from internal format
+    pub fn restore(&mut self, ymd: rp_pac::rtc::regs::Rtc1, hms: rp_pac::rtc::regs::Rtc0) {
+        // disable RTC while we configure it
+        self.inner.regs().ctrl().modify(|w| w.set_rtc_enable(false));
+        while self.inner.regs().ctrl().read().rtc_active() {
+            core::hint::spin_loop();
+        }
+
+        self.inner.regs().setup_0().write(|w| {
+            *w = rp_pac::rtc::regs::Setup0(ymd.0);
+        });
+        self.inner.regs().setup_1().write(|w| {
+            *w = rp_pac::rtc::regs::Setup1(hms.0);
+        });
+
+        // Load the new datetime and re-enable RTC
+        self.inner.regs().ctrl().write(|w| w.set_load(true));
+        self.inner.regs().ctrl().write(|w| w.set_rtc_enable(true));
+        while !self.inner.regs().ctrl().read().rtc_active() {
+            core::hint::spin_loop();
+        }
+    }
+
+    /// Get the time in internal format
+    pub fn save(&mut self) -> (rp_pac::rtc::regs::Rtc1, rp_pac::rtc::regs::Rtc0) {
+        let rtc_0: rp_pac::rtc::regs::Rtc0 = self.inner.regs().rtc_0().read();
+        let rtc_1 = self.inner.regs().rtc_1().read();
+        (rtc_1, rtc_0)
+    }
+
     /// Checks to see if this Rtc is running
     pub fn is_running(&self) -> bool {
         self.inner.regs().ctrl().read().rtc_active()

examples/rp/src/bin/rtc.rs

@@ -4,6 +4,7 @@
 
 use defmt::*;
 use embassy_executor::Spawner;
+use embassy_rp::pac::rtc::regs::{Rtc0, Rtc1};
 use embassy_rp::rtc::{DateTime, DayOfWeek, Rtc};
 use embassy_time::{Duration, Timer};
 use {defmt_rtt as _, panic_probe as _};
@@ -11,8 +12,16 @@ use {defmt_rtt as _, panic_probe as _};
 #[embassy_executor::main]
 async fn main(_spawner: Spawner) {
     let p = embassy_rp::init(Default::default());
-    info!("Hello World!");
+    info!("Wait for 20s");
 
+    let mut watchdog = embassy_rp::watchdog::Watchdog::new(p.WATCHDOG);
+    let mut rtc = Rtc::new(p.RTC);
+
+    let rtc0 = Rtc0(watchdog.get_scratch0());
+    let rtc1 = Rtc1(watchdog.get_scratch1());
+    if rtc1.year() >= 2020 {
+        rtc.restore(rtc1, rtc0);
+    } else {
         let now = DateTime {
             year: 2020,
             month: 5,
@@ -22,18 +31,22 @@ async fn main(_spawner: Spawner) {
             minute: 30,
             second: 50,
         };
+        rtc.set_datetime(now).unwrap();
+    }
 
-    let mut rtc = Rtc::new(p.RTC);
-    if rtc.set_datetime(now).is_ok() {
-        // In reality the delay would be much longer
     Timer::after(Duration::from_millis(20000)).await;
 
     if let Ok(dt) = rtc.now() {
         info!(
-                "Now: {}-{}-{} {}:{}:{}",
+            "Now: {}-{:02}-{:02} {}:{:02}:{:02}",
             dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second,
         );
+        let (rtc1, rtc0) = rtc.save();
+        watchdog.set_scratch0(rtc0.0);
+        watchdog.set_scratch1(rtc1.0);
     }
-    }
+
-    info!("Done.");
+    info!("Reboot.");
+    Timer::after(Duration::from_millis(200)).await;
+    cortex_m::peripheral::SCB::sys_reset();
 }