diff --git a/src/clocks/mod.rs b/src/clocks/mod.rs
index 420add3..7b4c5e0 100644
--- a/src/clocks/mod.rs
+++ b/src/clocks/mod.rs
@@ -36,7 +36,7 @@ cfg_if::cfg_if! {
 // todo: Continue working through DRY between the clock modules.
 
 /// Speed out of limits.
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, defmt::Format)]
 pub enum RccError {
     Speed,
     Hardware,
diff --git a/src/crc.rs b/src/crc.rs
index 6cac30c..664893e 100644
--- a/src/crc.rs
+++ b/src/crc.rs
@@ -313,7 +313,7 @@ impl Default for Polynomial {
 }
 
 /// Errors generated when trying to create invalid polynomials.
-#[derive(Copy, Clone, Debug, PartialEq)]
+#[derive(Copy, Clone, Debug, PartialEq, defmt::Format)]
 pub enum PolynomialError {
     /// Tried to create an even polynomial.
     /// The hardware CRC unit only supports odd polynomials.
diff --git a/src/flash/non_trustzone.rs b/src/flash/non_trustzone.rs
index 5481bc2..61bda6e 100644
--- a/src/flash/non_trustzone.rs
+++ b/src/flash/non_trustzone.rs
@@ -32,7 +32,7 @@ pub enum Bank {
     B2 = 1,
 }
 
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, defmt::Format)]
 /// Possible error states for flash operations.
 pub enum Error {
     /// Flash controller is not done yet
diff --git a/src/flash/trustzone.rs b/src/flash/trustzone.rs
index 7ebba4e..4baa3fb 100644
--- a/src/flash/trustzone.rs
+++ b/src/flash/trustzone.rs
@@ -32,7 +32,7 @@ pub enum Bank {
     B2 = 1,
 }
 
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, defmt::Format)]
 /// Possible error states for flash operations.
 pub enum Error {
     /// Flash controller is not done yet
diff --git a/src/i2c.rs b/src/i2c.rs
index c3ea631..92ec5af 100644
--- a/src/i2c.rs
+++ b/src/i2c.rs
@@ -63,7 +63,7 @@ macro_rules! busy_wait {
 
 /// I2C error
 #[non_exhaustive]
-#[derive(Debug)]
+#[derive(Debug, defmt::Format)]
 pub enum Error {
     /// Bus error
     Bus,
diff --git a/src/i2c_f4.rs b/src/i2c_f4.rs
index a1c72fd..01f2e1b 100644
--- a/src/i2c_f4.rs
+++ b/src/i2c_f4.rs
@@ -25,7 +25,7 @@ pub enum I2cDevice {
     Three,
 }
 
-#[derive(Debug)]
+#[derive(Debug, defmt::Format)]
 pub enum Error {
     OVERRUN,
     NACK,
diff --git a/src/qspi.rs b/src/qspi.rs
index 9743c59..ebfa90b 100644
--- a/src/qspi.rs
+++ b/src/qspi.rs
@@ -89,7 +89,7 @@ pub enum SamplingEdge {
 }
 
 /// Indicates an error with the QSPI peripheral.
-#[derive(Copy, Clone, PartialEq)]
+#[derive(Copy, Clone, PartialEq, defmt::Format)]
 pub enum QspiError {
     Busy,
     Underflow,
diff --git a/src/rtc.rs b/src/rtc.rs
index 484d19b..25abe08 100644
--- a/src/rtc.rs
+++ b/src/rtc.rs
@@ -26,7 +26,7 @@ pub enum RtcClockSource {
 }
 
 /// RTC error type
-#[derive(Debug)]
+#[derive(Debug, defmt::Format)]
 pub enum Error {
     /// Invalid input error
     InvalidInputData,
diff --git a/src/spi/mod.rs b/src/spi/mod.rs
index 8e8e11b..78135c7 100644
--- a/src/spi/mod.rs
+++ b/src/spi/mod.rs
@@ -53,7 +53,7 @@ macro_rules! check_errors {
 
 /// SPI error
 #[non_exhaustive]
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, defmt::Format)]
 pub enum SpiError {
     /// Overrun occurred
     Overrun,
diff --git a/src/timer.rs b/src/timer.rs
index c9d7a24..4156e47 100644
--- a/src/timer.rs
+++ b/src/timer.rs
@@ -53,7 +53,7 @@ pub static TICK_OVERFLOW_COUNT: AtomicU32 = AtomicU32::new(0);
 
 // todo: Low power timer enabling etc. eg on L4, RCC_APB1ENR1.LPTIM1EN
 
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, defmt::Format)]
 /// Used for when attempting to set a timer period that is out of range.
 pub struct ValueError {}
 
diff --git a/src/usart.rs b/src/usart.rs
index a6bef21..1e28083 100644
--- a/src/usart.rs
+++ b/src/usart.rs
@@ -93,7 +93,7 @@ pub enum IrdaMode {
 
 /// Serial error
 #[non_exhaustive]
-#[derive(Debug)]
+#[derive(Debug, defmt::Format)]
 pub enum UartError {
     /// Framing error
     Framing,