diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index 97c668ac..931a7bc0 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -57,6 +57,14 @@ jobs:
             features: nrf52840,defmt
           - package: embassy-rp-examples
             target: thumbv6m-none-eabi
+          - package: embassy-stm32
+            target: thumbv7em-none-eabi
+            features: stm32f411ce
+          - package: embassy-stm32
+            target: thumbv7em-none-eabi
+            features: stm32f429zi
+          - package: embassy-stm32-examples
+            target: thumbv7em-none-eabi
 
     steps:
       - uses: actions/checkout@v2
diff --git a/embassy-nrf/src/chips/nrf52805.rs b/embassy-nrf/src/chips/nrf52805.rs
index 272cabc0..f3ceb98e 100644
--- a/embassy-nrf/src/chips/nrf52805.rs
+++ b/embassy-nrf/src/chips/nrf52805.rs
@@ -153,7 +153,9 @@ impl_pin!(P0_30, 0, 30);
 impl_pin!(P0_31, 0, 31);
 
 pub mod irqs {
+    use crate::pac::Interrupt as InterruptEnum;
     use embassy_macros::interrupt_declare as declare;
+
     declare!(POWER_CLOCK);
     declare!(RADIO);
     declare!(UARTE0_UART0);
diff --git a/embassy-nrf/src/chips/nrf52810.rs b/embassy-nrf/src/chips/nrf52810.rs
index 9e9f8009..dae26054 100644
--- a/embassy-nrf/src/chips/nrf52810.rs
+++ b/embassy-nrf/src/chips/nrf52810.rs
@@ -158,7 +158,9 @@ impl_pin!(P0_30, 0, 30);
 impl_pin!(P0_31, 0, 31);
 
 pub mod irqs {
+    use crate::pac::Interrupt as InterruptEnum;
     use embassy_macros::interrupt_declare as declare;
+
     declare!(POWER_CLOCK);
     declare!(RADIO);
     declare!(UARTE0_UART0);
diff --git a/embassy-nrf/src/chips/nrf52811.rs b/embassy-nrf/src/chips/nrf52811.rs
index a9ef0ed1..6f9edff3 100644
--- a/embassy-nrf/src/chips/nrf52811.rs
+++ b/embassy-nrf/src/chips/nrf52811.rs
@@ -159,7 +159,9 @@ impl_pin!(P0_30, 0, 30);
 impl_pin!(P0_31, 0, 31);
 
 pub mod irqs {
+    use crate::pac::Interrupt as InterruptEnum;
     use embassy_macros::interrupt_declare as declare;
+
     declare!(POWER_CLOCK);
     declare!(RADIO);
     declare!(UARTE0_UART0);
diff --git a/embassy-nrf/src/chips/nrf52820.rs b/embassy-nrf/src/chips/nrf52820.rs
index d0a8b9e9..8bc50b6d 100644
--- a/embassy-nrf/src/chips/nrf52820.rs
+++ b/embassy-nrf/src/chips/nrf52820.rs
@@ -157,7 +157,9 @@ impl_pin!(P0_30, 0, 30);
 impl_pin!(P0_31, 0, 31);
 
 pub mod irqs {
+    use crate::pac::Interrupt as InterruptEnum;
     use embassy_macros::interrupt_declare as declare;
+
     declare!(POWER_CLOCK);
     declare!(RADIO);
     declare!(UARTE0_UART0);
diff --git a/embassy-nrf/src/chips/nrf52832.rs b/embassy-nrf/src/chips/nrf52832.rs
index 4e57f2fa..6f3f7fc7 100644
--- a/embassy-nrf/src/chips/nrf52832.rs
+++ b/embassy-nrf/src/chips/nrf52832.rs
@@ -172,7 +172,9 @@ impl_pin!(P0_30, 0, 30);
 impl_pin!(P0_31, 0, 31);
 
 pub mod irqs {
+    use crate::pac::Interrupt as InterruptEnum;
     use embassy_macros::interrupt_declare as declare;
+
     declare!(POWER_CLOCK);
     declare!(RADIO);
     declare!(UARTE0_UART0);
diff --git a/embassy-nrf/src/chips/nrf52833.rs b/embassy-nrf/src/chips/nrf52833.rs
index 30b0ab00..a0240b19 100644
--- a/embassy-nrf/src/chips/nrf52833.rs
+++ b/embassy-nrf/src/chips/nrf52833.rs
@@ -212,7 +212,9 @@ impl_pin!(P1_14, 1, 14);
 impl_pin!(P1_15, 1, 15);
 
 pub mod irqs {
+    use crate::pac::Interrupt as InterruptEnum;
     use embassy_macros::interrupt_declare as declare;
+
     declare!(POWER_CLOCK);
     declare!(RADIO);
     declare!(UARTE0_UART0);
diff --git a/embassy-nrf/src/chips/nrf52840.rs b/embassy-nrf/src/chips/nrf52840.rs
index 0b6c3f68..d4dcfd06 100644
--- a/embassy-nrf/src/chips/nrf52840.rs
+++ b/embassy-nrf/src/chips/nrf52840.rs
@@ -217,7 +217,9 @@ impl_pin!(P1_14, 1, 14);
 impl_pin!(P1_15, 1, 15);
 
 pub mod irqs {
+    use crate::pac::Interrupt as InterruptEnum;
     use embassy_macros::interrupt_declare as declare;
+
     declare!(POWER_CLOCK);
     declare!(RADIO);
     declare!(UARTE0_UART0);
diff --git a/embassy-rp/src/dma.rs b/embassy-rp/src/dma.rs
index 73be6d76..60c1b880 100644
--- a/embassy-rp/src/dma.rs
+++ b/embassy-rp/src/dma.rs
@@ -1,9 +1,8 @@
 use core::sync::atomic::{compiler_fence, Ordering};
 
-use defmt::{assert, *};
-
+use crate::fmt::{assert, *};
+use crate::pac::dma::vals;
 use crate::{pac, peripherals};
-use pac::dma::vals;
 
 pub struct Dma<T: Channel> {
     inner: T,
diff --git a/embassy-rp/src/interrupt.rs b/embassy-rp/src/interrupt.rs
index 262f7f54..a4e5959a 100644
--- a/embassy-rp/src/interrupt.rs
+++ b/embassy-rp/src/interrupt.rs
@@ -9,6 +9,7 @@ pub use embassy_extras::interrupt::Priority3 as Priority;
 
 mod irqs {
     use super::*;
+    use crate::pac::Interrupt as InterruptEnum;
 
     declare!(TIMER_IRQ_0);
     declare!(TIMER_IRQ_1);
diff --git a/embassy-rp/src/pll.rs b/embassy-rp/src/pll.rs
index 2726367e..fb643b01 100644
--- a/embassy-rp/src/pll.rs
+++ b/embassy-rp/src/pll.rs
@@ -1,6 +1,6 @@
 use core::ops::Deref;
-use defmt::{assert, *};
 
+use crate::fmt::{assert, *};
 use crate::pac;
 
 const XOSC_MHZ: u32 = 12;
diff --git a/embassy-stm32-examples/src/example_common.rs b/embassy-stm32-examples/src/example_common.rs
new file mode 100644
index 00000000..54d63383
--- /dev/null
+++ b/embassy-stm32-examples/src/example_common.rs
@@ -0,0 +1,17 @@
+#![macro_use]
+
+use defmt_rtt as _; // global logger
+use panic_probe as _;
+
+pub use defmt::*;
+
+use core::sync::atomic::{AtomicUsize, Ordering};
+
+defmt::timestamp! {"{=u64}", {
+        static COUNT: AtomicUsize = AtomicUsize::new(0);
+        // NOTE(no-CAS) `timestamps` runs with interrupts disabled
+        let n = COUNT.load(Ordering::Relaxed);
+        COUNT.store(n + 1, Ordering::Relaxed);
+        n as u64
+    }
+}
diff --git a/embassy-stm32/Cargo.toml b/embassy-stm32/Cargo.toml
index 3d5bb57c..81bd032c 100644
--- a/embassy-stm32/Cargo.toml
+++ b/embassy-stm32/Cargo.toml
@@ -19,6 +19,7 @@ futures = { version = "0.3.5", default-features = false, features = ["async-awai
 rand_core = { version = "0.6.2", optional = true }
 sdio-host = { version = "0.5.0", optional = true }
 embedded-sdmmc = { git = "https://github.com/thalesfragoso/embedded-sdmmc-rs", branch = "async", optional = true }
+critical-section = "0.2.1"
 
 [build-dependencies]
 regex = "1.4.6"
diff --git a/embassy-stm32/src/dma/v2.rs b/embassy-stm32/src/dma/v2.rs
index 63d0586f..0dfa01dc 100644
--- a/embassy-stm32/src/dma/v2.rs
+++ b/embassy-stm32/src/dma/v2.rs
@@ -184,4 +184,4 @@ pub(crate) unsafe fn init() {
     interrupt::DMA2_Stream5::steal().enable();
     interrupt::DMA2_Stream6::steal().enable();
     interrupt::DMA2_Stream7::steal().enable();
-}
\ No newline at end of file
+}
diff --git a/embassy-stm32/src/fmt.rs b/embassy-stm32/src/fmt.rs
new file mode 100644
index 00000000..160642cc
--- /dev/null
+++ b/embassy-stm32/src/fmt.rs
@@ -0,0 +1,114 @@
+#![macro_use]
+#![allow(clippy::module_inception)]
+#![allow(unused)]
+
+#[cfg(all(feature = "defmt", feature = "log"))]
+compile_error!("You may not enable both `defmt` and `log` features.");
+
+pub use fmt::*;
+
+#[cfg(feature = "defmt")]
+mod fmt {
+    pub use defmt::{
+        assert, assert_eq, assert_ne, debug, debug_assert, debug_assert_eq, debug_assert_ne, error,
+        info, panic, todo, trace, unreachable, unwrap, warn,
+    };
+}
+
+#[cfg(feature = "log")]
+mod fmt {
+    pub use core::{
+        assert, assert_eq, assert_ne, debug_assert, debug_assert_eq, debug_assert_ne, panic, todo,
+        unreachable,
+    };
+    pub use log::{debug, error, info, trace, warn};
+}
+
+#[cfg(not(any(feature = "defmt", feature = "log")))]
+mod fmt {
+    #![macro_use]
+
+    pub use core::{
+        assert, assert_eq, assert_ne, debug_assert, debug_assert_eq, debug_assert_ne, panic, todo,
+        unreachable,
+    };
+
+    macro_rules! trace {
+        ($($msg:expr),+ $(,)?) => {
+            ()
+        };
+    }
+
+    macro_rules! debug {
+        ($($msg:expr),+ $(,)?) => {
+            ()
+        };
+    }
+
+    macro_rules! info {
+        ($($msg:expr),+ $(,)?) => {
+            ()
+        };
+    }
+
+    macro_rules! warn {
+        ($($msg:expr),+ $(,)?) => {
+            ()
+        };
+    }
+
+    macro_rules! error {
+        ($($msg:expr),+ $(,)?) => {
+            ()
+        };
+    }
+}
+
+#[cfg(not(feature = "defmt"))]
+macro_rules! unwrap {
+    ($arg:expr) => {
+        match $crate::fmt::Try::into_result($arg) {
+            ::core::result::Result::Ok(t) => t,
+            ::core::result::Result::Err(e) => {
+                ::core::panic!("unwrap of `{}` failed: {:?}", ::core::stringify!($arg), e);
+            }
+        }
+    };
+    ($arg:expr, $($msg:expr),+ $(,)? ) => {
+        match $crate::fmt::Try::into_result($arg) {
+            ::core::result::Result::Ok(t) => t,
+            ::core::result::Result::Err(e) => {
+                ::core::panic!("unwrap of `{}` failed: {}: {:?}", ::core::stringify!($arg), ::core::format_args!($($msg,)*), e);
+            }
+        }
+    }
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub struct NoneError;
+
+pub trait Try {
+    type Ok;
+    type Error;
+    fn into_result(self) -> Result<Self::Ok, Self::Error>;
+}
+
+impl<T> Try for Option<T> {
+    type Ok = T;
+    type Error = NoneError;
+
+    #[inline]
+    fn into_result(self) -> Result<T, NoneError> {
+        self.ok_or(NoneError)
+    }
+}
+
+impl<T, E> Try for Result<T, E> {
+    type Ok = T;
+    type Error = E;
+
+    #[inline]
+    fn into_result(self) -> Self {
+        self
+    }
+}
diff --git a/embassy-stm32/src/usart/v1.rs b/embassy-stm32/src/usart/v1.rs
index 78a53b53..5fbe1438 100644
--- a/embassy-stm32/src/usart/v1.rs
+++ b/embassy-stm32/src/usart/v1.rs
@@ -103,7 +103,11 @@ impl<'d, T: Instance> Uart<'d, T> {
     }
 
     #[cfg(feature = "_dma_v2")]
-    pub async fn write_dma(&mut self, ch: &mut impl crate::dma::Channel, buffer: &[u8]) -> Result<(), Error> {
+    pub async fn write_dma(
+        &mut self,
+        ch: &mut impl crate::dma::Channel,
+        buffer: &[u8],
+    ) -> Result<(), Error> {
         let ch_func = 4; // USART3_TX
         let r = self.inner.regs();
 
diff --git a/embassy-stm32/src/usart/v2.rs b/embassy-stm32/src/usart/v2.rs
index e69de29b..8b137891 100644
--- a/embassy-stm32/src/usart/v2.rs
+++ b/embassy-stm32/src/usart/v2.rs
@@ -0,0 +1 @@
+
diff --git a/embassy-traits/src/lib.rs b/embassy-traits/src/lib.rs
index 04741787..3d84cf07 100644
--- a/embassy-traits/src/lib.rs
+++ b/embassy-traits/src/lib.rs
@@ -11,6 +11,6 @@ pub mod delay;
 pub mod flash;
 pub mod gpio;
 pub mod i2c;
+pub mod rng;
 pub mod spi;
 pub mod uart;
-pub mod rng;