configure RCC to use 48MHz MSI as system clock

Cargo.toml

@@ -23,4 +23,4 @@ chrono = { version = "^0.4", default-features = false }
 
 [profile.release]
 debug = 2
-opt-level = "s"
+opt-level = 3

src/main.rs

@@ -3,13 +3,20 @@
 
 use defmt::*;
 use embassy_executor::Spawner;
-use embassy_stm32::gpio::{Level, Output, Speed};
+use embassy_stm32::{Config, gpio::{Level, Output, Speed}, rcc::{MSIRange, Sysclk, mux}};
 use embassy_time::Timer;
 use {defmt_rtt as _, panic_probe as _};
 
 #[embassy_executor::main]
 async fn main(_spawner: Spawner) {
-    let p = embassy_stm32::init(Default::default());
+    let mut config = Config::default();
+    {
+        config.rcc.msi = Some(MSIRange::RANGE48M);
+        config.rcc.sys = Sysclk::MSI;
+        config.rcc.mux.rngsel = mux::Rngsel::MSI;
+        config.enable_debug_during_sleep = true;
+    }
+    let p = embassy_stm32::init(config);
     info!("hiiiiiiii :3");
 
     let mut led = Output::new(p.PB5, Level::High, Speed::Low);