stm32/rtc: fix datetime and add f4 test

tests/stm32/src/bin/rtc.rs

@@ -0,0 +1,52 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+// required-features: chrono
+
+#[path = "../example_common.rs"]
+mod example_common;
+use chrono::{NaiveDate, NaiveDateTime};
+use defmt::assert;
+use embassy_executor::Spawner;
+use embassy_stm32::pac;
+use embassy_stm32::rtc::{Rtc, RtcConfig};
+use embassy_time::{Duration, Timer};
+use example_common::*;
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_stm32::init(config());
+    info!("Hello World!");
+
+    let now = NaiveDate::from_ymd_opt(2020, 5, 15)
+        .unwrap()
+        .and_hms_opt(10, 30, 15)
+        .unwrap();
+
+    info!("Starting LSI");
+
+    unsafe {
+        pac::RCC.csr().modify(|w| w.set_lsion(true));
+        while !pac::RCC.csr().read().lsirdy() {}
+    }
+
+    info!("Started LSI");
+
+    let mut rtc = Rtc::new(p.RTC, RtcConfig::default());
+
+    rtc.set_datetime(now.into()).expect("datetime not set");
+
+    info!("Waiting 5 seconds");
+    Timer::after(Duration::from_millis(5000)).await;
+
+    let then: NaiveDateTime = rtc.now().unwrap().into();
+    let seconds = (then - now).num_seconds();
+
+    defmt::info!("measured = {}", seconds);
+
+    assert!(seconds > 3 && seconds < 7);
+
+    info!("Test OK");
+    cortex_m::asm::bkpt();
+}