Update changelog with MonoTimer frequency fix
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
## [Unreleased]
+### Fixed
+
+- Wrong frequency reported by `MonoTimer` ([#56](https://github.com/stm32-rs/stm32f3xx-hal/pull/56))
+
## [v0.4.1] - 2020-03-07
### Added
