diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6d22d3d92..34982fe25 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+### Changed
+
+- Use `u8` as default SPI as Serial Word type
+
 ### Added
 - Added `Can` Controller Area Network traits.
 - `Error` traits for SPI, I2C and Serial traits. The error types used in those must
diff --git a/src/serial/blocking.rs b/src/serial/blocking.rs
index 84bc632be..7b9c8a9d2 100644
--- a/src/serial/blocking.rs
+++ b/src/serial/blocking.rs
@@ -1,7 +1,7 @@
 //! Blocking serial API
 
 /// Write half of a serial interface (blocking variant)
-pub trait Write<Word> {
+pub trait Write<Word = u8> {
     /// The type of error that can occur when writing
     type Error: crate::serial::Error;
 
diff --git a/src/serial/nb.rs b/src/serial/nb.rs
index 13a845d10..bb0467d66 100644
--- a/src/serial/nb.rs
+++ b/src/serial/nb.rs
@@ -4,7 +4,7 @@
 ///
 /// Some serial interfaces support different data sizes (8 bits, 9 bits, etc.);
 /// This can be encoded in this trait via the `Word` type parameter.
-pub trait Read<Word> {
+pub trait Read<Word = u8> {
     /// Read error
     type Error: crate::serial::Error;
 
@@ -21,7 +21,7 @@ impl<T: Read<Word>, Word> Read<Word> for &mut T {
 }
 
 /// Write half of a serial interface
-pub trait Write<Word> {
+pub trait Write<Word = u8> {
     /// Write error
     type Error: crate::serial::Error;
 
diff --git a/src/spi/blocking.rs b/src/spi/blocking.rs
index d2d916aae..1f8f1e8fd 100644
--- a/src/spi/blocking.rs
+++ b/src/spi/blocking.rs
@@ -1,7 +1,7 @@
 //! Blocking SPI API
 
 /// Blocking transfer
-pub trait Transfer<W> {
+pub trait Transfer<W = u8> {
     /// Error type
     type Error: crate::spi::Error;
 
@@ -20,7 +20,7 @@ impl<T: Transfer<W>, W> Transfer<W> for &mut T {
 }
 
 /// Blocking write
-pub trait Write<W> {
+pub trait Write<W = u8> {
     /// Error type
     type Error: crate::spi::Error;
 
@@ -37,7 +37,7 @@ impl<T: Write<W>, W> Write<W> for &mut T {
 }
 
 /// Blocking write (iterator version)
-pub trait WriteIter<W> {
+pub trait WriteIter<W = u8> {
     /// Error type
     type Error: crate::spi::Error;
 
@@ -62,7 +62,7 @@ impl<T: WriteIter<W>, W> WriteIter<W> for &mut T {
 ///
 /// This allows composition of SPI operations into a single bus transaction
 #[derive(Debug, PartialEq)]
-pub enum Operation<'a, W: 'static> {
+pub enum Operation<'a, W: 'static = u8> {
     /// Write data from the provided buffer, discarding read data
     Write(&'a [W]),
     /// Write data out while reading data into the provided buffer
@@ -71,7 +71,7 @@ pub enum Operation<'a, W: 'static> {
 
 /// Transactional trait allows multiple actions to be executed
 /// as part of a single SPI transaction
-pub trait Transactional<W: 'static> {
+pub trait Transactional<W: 'static = u8> {
     /// Associated error type
     type Error: crate::spi::Error;
 
diff --git a/src/spi/nb.rs b/src/spi/nb.rs
index c7d377ef9..6d540a762 100644
--- a/src/spi/nb.rs
+++ b/src/spi/nb.rs
@@ -16,7 +16,7 @@
 ///
 /// - Some SPIs can work with 8-bit *and* 16-bit words. You can overload this trait with different
 /// `Word` types to allow operation in both modes.
-pub trait FullDuplex<Word> {
+pub trait FullDuplex<Word = u8> {
     /// An enumeration of SPI errors
     type Error: crate::spi::Error;