diff --git a/CHANGELOG.md b/CHANGELOG.md
index fd5048a..9a5893d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,15 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## [unreleased]
+
+## [v0.4.0]
+
+### Changed
+
+- Replaced `Hertz` by `impl Into<Hertz>` completely and removed
+  `+ Copy` where not necessary
+
 ## [v0.3.1]
 
 - Updated all links to point to new repository
diff --git a/Cargo.toml b/Cargo.toml
index 4076097..b8c0ca7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "va108xx-hal"
-version = "0.3.1"
+version = "0.4.0"
 authors = ["Robin Mueller <muellerr@irs.uni-stuttgart.de>"]
 edition = "2021"
 description = "HAL for the Vorago VA108xx family of microcontrollers"
diff --git a/examples/spi.rs b/examples/spi.rs
index 33daf31..59445e0 100644
--- a/examples/spi.rs
+++ b/examples/spi.rs
@@ -114,12 +114,8 @@ fn main() -> ! {
     match SPI_BUS_SEL {
         SpiBusSelect::SpiAPortA | SpiBusSelect::SpiAPortB => {
             if let Some(ref mut spi) = *spia_ref.borrow_mut() {
-                let transfer_cfg = TransferConfig::new_no_hw_cs(
-                    SPI_SPEED_KHZ.khz().into(),
-                    SPI_MODE,
-                    BLOCKMODE,
-                    false,
-                );
+                let transfer_cfg =
+                    TransferConfig::new_no_hw_cs(SPI_SPEED_KHZ.khz(), SPI_MODE, BLOCKMODE, false);
                 spi.cfg_transfer(&transfer_cfg);
             }
         }
@@ -127,7 +123,7 @@ fn main() -> ! {
             if let Some(ref mut spi) = *spib_ref.borrow_mut() {
                 let hw_cs_pin = pinsb.pb2.into_funsel_1();
                 let transfer_cfg = TransferConfig::new(
-                    SPI_SPEED_KHZ.khz().into(),
+                    SPI_SPEED_KHZ.khz(),
                     SPI_MODE,
                     Some(hw_cs_pin),
                     BLOCKMODE,
diff --git a/examples/uart.rs b/examples/uart.rs
index 1aa72dd..8f6ed31 100644
--- a/examples/uart.rs
+++ b/examples/uart.rs
@@ -25,7 +25,7 @@ fn main() -> ! {
         (tx, rx),
         115200.bps(),
         &mut dp.SYSCONFIG,
-        50.mhz().into(),
+        50.mhz(),
     );
     let (mut tx, mut rx) = uartb.split();
     writeln!(tx, "Hello World\r").unwrap();
diff --git a/src/i2c.rs b/src/i2c.rs
index 0134831..507f8fd 100644
--- a/src/i2c.rs
+++ b/src/i2c.rs
@@ -231,7 +231,7 @@ macro_rules! i2c_base {
             impl I2cBase<$I2CX> {
                 pub fn $i2cx(
                     i2c: $I2CX,
-                    sys_clk: impl Into<Hertz> + Copy,
+                    sys_clk: impl Into<Hertz>,
                     speed_mode: I2cSpeed,
                     ms_cfg: Option<&MasterConfig>,
                     sl_cfg: Option<&SlaveConfig>,
@@ -740,7 +740,7 @@ macro_rules! i2c_slave {
                 fn $i2cx_slave(
                     i2c: $I2CX,
                     cfg: SlaveConfig,
-                    sys_clk: impl Into<Hertz> + Copy,
+                    sys_clk: impl Into<Hertz>,
                     speed_mode: I2cSpeed,
                     sys_cfg: Option<&mut SYSCONFIG>,
                 ) -> Self {
@@ -897,7 +897,7 @@ macro_rules! i2c_slave {
                 pub fn i2ca(
                     i2c: $I2CX,
                     cfg: SlaveConfig,
-                    sys_clk: impl Into<Hertz> + Copy,
+                    sys_clk: impl Into<Hertz>,
                     speed_mode: I2cSpeed,
                     sys_cfg: Option<&mut SYSCONFIG>,
                 ) -> Result<Self, Error> {
@@ -912,7 +912,7 @@ macro_rules! i2c_slave {
                 pub fn $i2cx(
                     i2c: $I2CX,
                     cfg: SlaveConfig,
-                    sys_clk: impl Into<Hertz> + Copy,
+                    sys_clk: impl Into<Hertz>,
                     speed_mode: I2cSpeed,
                     sys_cfg: Option<&mut SYSCONFIG>,
                 ) -> Self {
diff --git a/src/spi.rs b/src/spi.rs
index 36cd58e..f4208b7 100644
--- a/src/spi.rs
+++ b/src/spi.rs
@@ -218,9 +218,9 @@ pub struct ReducedTransferConfig {
 }
 
 impl TransferConfig<NoneT> {
-    pub fn new_no_hw_cs(spi_clk: Hertz, mode: Mode, blockmode: bool, sod: bool) -> Self {
+    pub fn new_no_hw_cs(spi_clk: impl Into<Hertz>, mode: Mode, blockmode: bool, sod: bool) -> Self {
         TransferConfig {
-            spi_clk,
+            spi_clk: spi_clk.into(),
             mode,
             hw_cs: None,
             sod,
@@ -231,14 +231,14 @@ impl TransferConfig<NoneT> {
 
 impl<HWCS: HwCs> TransferConfig<HWCS> {
     pub fn new(
-        spi_clk: Hertz,
+        spi_clk: impl Into<Hertz>,
         mode: Mode,
         hw_cs: Option<HWCS>,
         blockmode: bool,
         sod: bool,
     ) -> Self {
         TransferConfig {
-            spi_clk,
+            spi_clk: spi_clk.into(),
             mode,
             hw_cs,
             sod,
@@ -452,7 +452,7 @@ macro_rules! spi {
                 }
 
                 #[inline]
-                pub fn cfg_clock(&mut self, spi_clk: Hertz) {
+                pub fn cfg_clock(&mut self, spi_clk: impl Into<Hertz>) {
                     self.spi_base.cfg_clock(spi_clk);
                 }
 
@@ -482,8 +482,8 @@ macro_rules! spi {
 
             impl<WORD: Word> SpiBase<$SPIX, WORD> {
                 #[inline]
-                pub fn cfg_clock(&mut self, spi_clk: Hertz) {
-                    let clk_prescale = self.sys_clk.0 / (spi_clk.0 * (self.cfg.scrdv as u32 + 1));
+                pub fn cfg_clock(&mut self, spi_clk: impl Into<Hertz>) {
+                    let clk_prescale = self.sys_clk.0 / (spi_clk.into().0 * (self.cfg.scrdv as u32 + 1));
                     self.spi
                         .clkprescale
                         .write(|w| unsafe { w.bits(clk_prescale) });
diff --git a/src/uart.rs b/src/uart.rs
index b33c3f7..fbb430d 100644
--- a/src/uart.rs
+++ b/src/uart.rs
@@ -306,12 +306,12 @@ macro_rules! uart_impl {
                     pins: PINS,
                     config: impl Into<Config>,
                     syscfg: &mut SYSCONFIG,
-                    sys_clk: Hertz
+                    sys_clk: impl Into<Hertz>
                 ) -> Self
                 {
                     enable_peripheral_clock(syscfg, $clk_enb_enum);
                     Uart { uart, pins, tx: Tx::new(), rx: Rx::new() }.init(
-                        config.into(), sys_clk
+                        config.into(), sys_clk.into()
                     )
                 }
             }