f4-rcc: Add option to enable debug_wfe and add hello example

examples/stm32f4/src/bin/hello.rs

@@ -0,0 +1,34 @@
+#![no_std]
+#![no_main]
+#![feature(trait_alias)]
+#![feature(min_type_alias_impl_trait)]
+#![feature(impl_trait_in_bindings)]
+#![feature(type_alias_impl_trait)]
+#![allow(incomplete_features)]
+
+use defmt::{info, panic};
+use embassy::executor::Spawner;
+use embassy::time::{Duration, Timer};
+use embassy_stm32::rcc::Config as RccConfig;
+use embassy_stm32::time::Hertz;
+use embassy_stm32::Config;
+use embassy_stm32::Peripherals;
+
+#[path = "../example_common.rs"]
+mod example_common;
+
+fn config() -> Config {
+    let mut rcc_config = RccConfig::default();
+    rcc_config.sys_ck = Some(Hertz(32_000_000));
+    rcc_config.enable_debug_wfe = true;
+
+    Config::default().rcc(rcc_config)
+}
+
+#[embassy::main(config = "config()")]
+async fn main(_spawner: Spawner, _p: Peripherals) -> ! {
+    loop {
+        info!("Hello World!");
+        Timer::after(Duration::from_secs(1)).await;
+    }
+}