Enable RTC on STM32WL chips (#1645)

* Add clippy allow to not report if same then branch

* Support enabling RTC clock on STM32WL

* Add clippy allow to not report if same then branch

* Support enabling RTC clock on STM32WL

* Add rtc example for stm32wl

* Address code review feedback

3 files changed, 47 insertions, 3 deletions

diff --git a/examples/stm32wl/.cargo/config.toml b/examples/stm32wl/.cargo/config.toml
index 4f8094ff2..ee416fcbc 100644
--- a/examples/stm32wl/.cargo/config.toml
+++ b/examples/stm32wl/.cargo/config.toml
@@ -3,7 +3,7 @@
 runner = "probe-rs run --chip STM32WLE5JCIx"
 
 [build]
-target = "thumbv7em-none-eabihf"
+target = "thumbv7em-none-eabi"
 
 [env]
 DEFMT_LOG = "trace"
diff --git a/examples/stm32wl/Cargo.toml b/examples/stm32wl/Cargo.toml
index 99f68387f..e2c66f456 100644
--- a/examples/stm32wl/Cargo.toml
+++ b/examples/stm32wl/Cargo.toml
@@ -8,8 +8,8 @@ license = "MIT OR Apache-2.0"
 embassy-sync = { version = "0.2.0", path = "../../embassy-sync", features = ["defmt"] }
 embassy-executor = { version = "0.2.0", path = "../../embassy-executor", features = ["nightly", "arch-cortex-m", "executor-thread", "defmt", "integrated-timers"] }
 embassy-time = { version = "0.1.2", path = "../../embassy-time", features = ["nightly", "unstable-traits", "defmt", "defmt-timestamp-uptime", "tick-hz-32_768"] }
-embassy-stm32 = { version = "0.1.0", path = "../../embassy-stm32", features = ["nightly", "unstable-traits", "defmt", "stm32wl55jc-cm4", "time-driver-any", "memory-x", "unstable-pac", "exti"]  }
-embassy-embedded-hal = {version = "0.1.0", path = "../../embassy-embedded-hal" }
+embassy-stm32 = { version = "0.1.0", path = "../../embassy-stm32", features = ["nightly", "unstable-traits", "defmt", "stm32wl55jc-cm4", "time-driver-any", "memory-x", "unstable-pac", "exti", "chrono"] }
+embassy-embedded-hal = { version = "0.1.0", path = "../../embassy-embedded-hal" }
 embassy-lora = { version = "0.1.0", path = "../../embassy-lora", features = ["stm32wl", "time", "defmt"] }
 lora-phy = { version = "1" }
 lorawan-device = { version = "0.10.0", default-features = false, features = ["async", "external-lora-phy"] }
@@ -25,6 +25,7 @@ embedded-storage = "0.3.0"
 panic-probe = { version = "0.3", features = ["print-defmt"] }
 futures = { version = "0.3.17", default-features = false, features = ["async-await"] }
 heapless = { version = "0.7.5", default-features = false }
+chrono = { version = "^0.4", default-features = false }
 
 [patch.crates-io]
 lora-phy = { git = "https://github.com/embassy-rs/lora-phy", rev = "ad289428fd44b02788e2fa2116445cc8f640a265" }
diff --git a/examples/stm32wl/src/bin/rtc.rs b/examples/stm32wl/src/bin/rtc.rs
new file mode 100644
index 000000000..e11825499
--- /dev/null
+++ b/examples/stm32wl/src/bin/rtc.rs
@@ -0,0 +1,43 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use chrono::{NaiveDate, NaiveDateTime};
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_stm32::rcc::{self, ClockSrc};
+use embassy_stm32::rtc::{Rtc, RtcConfig};
+use embassy_stm32::Config;
+use embassy_time::{Duration, Timer};
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = {
+        let mut config = Config::default();
+        config.rcc.mux = ClockSrc::HSE32;
+        config.rcc.rtc_mux = rcc::RtcClockSource::LSE32;
+        config.rcc.enable_rtc_apb = true;
+        embassy_stm32::init(config)
+    };
+    info!("Hello World!");
+
+    let now = NaiveDate::from_ymd_opt(2020, 5, 15)
+        .unwrap()
+        .and_hms_opt(10, 30, 15)
+        .unwrap();
+
+    let mut rtc = Rtc::new(
+        p.RTC,
+        RtcConfig::default().clock_config(embassy_stm32::rtc::RtcClockSource::LSE),
+    );
+    info!("Got RTC! {:?}", now.timestamp());
+
+    rtc.set_datetime(now.into()).expect("datetime not set");
+
+    // In reality the delay would be much longer
+    Timer::after(Duration::from_millis(20000)).await;
+
+    let then: NaiveDateTime = rtc.now().unwrap().into();
+    info!("Got RTC! {:?}", then.timestamp());
+}