prelude: add prelude

Author: astapleton

src/lib.rs

@@ -36,3 +36,6 @@ pub use crate::stm32 as device;
 #[cfg(feature = "rt")]
 #[cfg_attr(docsrs, doc(cfg(feature = "rt")))]
 pub use crate::stm32::interrupt;
+
+#[cfg(feature = "device-selected")]
+pub mod prelude;

src/prelude.rs

@@ -0,0 +1,4 @@
+//! Prelude
+pub use embedded_hal::prelude::*;
+
+pub use fugit::{ExtU32 as _, RateExtU32 as _};