Add embassy-boot

Embassy-boot is a simple bootloader that works together with an
application to provide firmware update capabilities with a minimal risk.

The bootloader consists of a platform-independent part, which implements
the swap algorithm, and a platform-dependent part (currently only for
nRF) that provides addition functionality such as watchdog timers
softdevice support.

22 files changed, 1705 insertions, 0 deletions

diff --git a/embassy-boot/boot/Cargo.toml b/embassy-boot/boot/Cargo.toml
new file mode 100644
index 000000000..0a3006ffc
--- /dev/null
+++ b/embassy-boot/boot/Cargo.toml
@@ -0,0 +1,23 @@
+[package]
+authors = [
+    "Ulf Lilleengen <[email protected]>",
+]
+edition = "2018"
+name = "embassy-boot"
+version = "0.1.0"
+description = "Bootloader using Embassy"
+
+[lib]
+
+[dependencies]
+defmt = { version = "0.3", optional = true }
+log = { version = "0.4", optional = true  }
+embassy = { path = "../../embassy", default-features = false }
+embedded-storage = "0.3.0"
+embedded-storage-async = "0.3.0"
+
+[dev-dependencies]
+log = "0.4"
+env_logger = "0.9"
+rand = "0.8"
+futures = { version = "0.3", features = ["executor"] }
diff --git a/embassy-boot/boot/src/fmt.rs b/embassy-boot/boot/src/fmt.rs
new file mode 100644
index 000000000..066970813
--- /dev/null
+++ b/embassy-boot/boot/src/fmt.rs
@@ -0,0 +1,225 @@
+#![macro_use]
+#![allow(unused_macros)]
+
+#[cfg(all(feature = "defmt", feature = "log"))]
+compile_error!("You may not enable both `defmt` and `log` features.");
+
+macro_rules! assert {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert!($($x)*);
+        }
+    };
+}
+
+macro_rules! assert_eq {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert_eq!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert_eq!($($x)*);
+        }
+    };
+}
+
+macro_rules! assert_ne {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert_ne!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert_ne!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert_eq {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert_eq!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert_eq!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert_ne {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert_ne!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert_ne!($($x)*);
+        }
+    };
+}
+
+macro_rules! todo {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::todo!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::todo!($($x)*);
+        }
+    };
+}
+
+macro_rules! unreachable {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::unreachable!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::unreachable!($($x)*);
+        }
+    };
+}
+
+macro_rules! panic {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::panic!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::panic!($($x)*);
+        }
+    };
+}
+
+macro_rules! trace {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::trace!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::trace!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! debug {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::debug!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! info {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::info!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::info!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! warn {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::warn!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::warn!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! error {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::error!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::error!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+#[cfg(feature = "defmt")]
+macro_rules! unwrap {
+    ($($x:tt)*) => {
+        ::defmt::unwrap!($($x)*)
+    };
+}
+
+#[cfg(not(feature = "defmt"))]
+macro_rules! unwrap {
+    ($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-boot/boot/src/lib.rs b/embassy-boot/boot/src/lib.rs
new file mode 100644
index 000000000..909397b7b
--- /dev/null
+++ b/embassy-boot/boot/src/lib.rs
@@ -0,0 +1,550 @@
+#![feature(type_alias_impl_trait)]
+#![feature(generic_associated_types)]
+#![no_std]
+///! embassy-boot is a bootloader and firmware updater for embedded devices with flash
+///! storage implemented using embedded-storage
+///!
+///! The bootloader works in conjunction with the firmware application, and only has the
+///! ability to manage two flash banks with an active and a updatable part. It implements
+///! a swap algorithm that is power-failure safe, and allows reverting to the previous
+///! version of the firmware, should the application crash and fail to mark itself as booted.
+///!
+///! This library is intended to be used by platform-specific bootloaders, such as embassy-boot-nrf,
+///! which defines the limits and flash type for that particular platform.
+///!
+mod fmt;
+
+use embedded_storage::nor_flash::{NorFlash, ReadNorFlash};
+use embedded_storage_async::nor_flash::AsyncNorFlash;
+
+pub const BOOT_MAGIC: u32 = 0xD00DF00D;
+pub const SWAP_MAGIC: u32 = 0xF00FDAAD;
+
+#[derive(Copy, Clone, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct Partition {
+    pub from: usize,
+    pub to: usize,
+}
+
+impl Partition {
+    pub const fn new(from: usize, to: usize) -> Self {
+        Self { from, to }
+    }
+    pub const fn len(&self) -> usize {
+        self.to - self.from
+    }
+}
+
+#[derive(PartialEq, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum State {
+    Boot,
+    Swap,
+}
+
+#[derive(PartialEq, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum BootError<E> {
+    Flash(E),
+    BadMagic,
+}
+
+impl<E> From<E> for BootError<E> {
+    fn from(error: E) -> Self {
+        BootError::Flash(error)
+    }
+}
+
+/// BootLoader works with any flash implementing embedded_storage and can also work with
+/// different page sizes.
+pub struct BootLoader<const PAGE_SIZE: usize> {
+    // Page with current state of bootloader. The state partition has the following format:
+    // | Range    | Description                                                                                        |
+    // | 0 - 4    | Magic indicating bootloader state. BOOT_MAGIC means boot, SWAP_MAGIC means swap. |
+    // | 4 - N    | Progress index used while swapping or reverting                                                    |
+    state: Partition,
+    // Location of the partition which will be booted from
+    active: Partition,
+    // Location of the partition which will be swapped in when requested
+    dfu: Partition,
+}
+
+impl<const PAGE_SIZE: usize> BootLoader<PAGE_SIZE> {
+    pub fn new(active: Partition, dfu: Partition, state: Partition) -> Self {
+        assert_eq!(active.len() % PAGE_SIZE, 0);
+        assert_eq!(dfu.len() % PAGE_SIZE, 0);
+        // DFU partition must have an extra page
+        assert!(dfu.len() - active.len() >= PAGE_SIZE);
+        // Ensure we have enough progress pages to store copy progress
+        assert!(active.len() / PAGE_SIZE >= (state.len() - 4) / PAGE_SIZE);
+        Self { active, dfu, state }
+    }
+
+    pub fn boot_address(&self) -> usize {
+        self.active.from
+    }
+
+    /// Perform necessary boot preparations like swapping images.
+    ///
+    /// The DFU partition is assumed to be 1 page bigger than the active partition for the swap
+    /// algorithm to work correctly.
+    ///
+    /// SWAPPING
+    ///
+    /// Assume a flash size of 3 pages for the active partition, and 4 pages for the DFU partition.
+    /// The swap index contains the copy progress, as to allow continuation of the copy process on
+    /// power failure. The index counter is represented within 1 or more pages (depending on total
+    /// flash size), where a page X is considered swapped if index at location (X + WRITE_SIZE)
+    /// contains a zero value. This ensures that index updates can be performed atomically and
+    /// avoid a situation where the wrong index value is set (page write size is "atomic").
+    ///
+    /// +-----------+------------+--------+--------+--------+--------+
+    /// | Partition | Swap Index | Page 0 | Page 1 | Page 3 | Page 4 |
+    /// +-----------+------------+--------+--------+--------+--------+
+    /// |    Active |          0 |      1 |      2 |      3 |      - |
+    /// |       DFU |          0 |      3 |      2 |      1 |      X |
+    /// +-----------+-------+--------+--------+--------+--------+
+    ///
+    /// The algorithm starts by copying 'backwards', and after the first step, the layout is
+    /// as follows:
+    ///
+    /// +-----------+------------+--------+--------+--------+--------+
+    /// | Partition | Swap Index | Page 0 | Page 1 | Page 3 | Page 4 |
+    /// +-----------+------------+--------+--------+--------+--------+
+    /// |    Active |          1 |      1 |      2 |      1 |      - |
+    /// |       DFU |          1 |      3 |      2 |      1 |      3 |
+    /// +-----------+------------+--------+--------+--------+--------+
+    ///
+    /// The next iteration performs the same steps
+    ///
+    /// +-----------+------------+--------+--------+--------+--------+
+    /// | Partition | Swap Index | Page 0 | Page 1 | Page 3 | Page 4 |
+    /// +-----------+------------+--------+--------+--------+--------+
+    /// |    Active |          2 |      1 |      2 |      1 |      - |
+    /// |       DFU |          2 |      3 |      2 |      2 |      3 |
+    /// +-----------+------------+--------+--------+--------+--------+
+    ///
+    /// And again until we're done
+    ///
+    /// +-----------+------------+--------+--------+--------+--------+
+    /// | Partition | Swap Index | Page 0 | Page 1 | Page 3 | Page 4 |
+    /// +-----------+------------+--------+--------+--------+--------+
+    /// |    Active |          3 |      3 |      2 |      1 |      - |
+    /// |       DFU |          3 |      3 |      1 |      2 |      3 |
+    /// +-----------+------------+--------+--------+--------+--------+
+    ///
+    /// REVERTING
+    ///
+    /// The reverting algorithm uses the swap index to discover that images were swapped, but that
+    /// the application failed to mark the boot successful. In this case, the revert algorithm will
+    /// run.
+    ///
+    /// The revert index is located separately from the swap index, to ensure that revert can continue
+    /// on power failure.
+    ///
+    /// The revert algorithm works forwards, by starting copying into the 'unused' DFU page at the start.
+    ///
+    /// +-----------+--------------+--------+--------+--------+--------+
+    /// | Partition | Revert Index | Page 0 | Page 1 | Page 3 | Page 4 |
+    //*/
+    /// +-----------+--------------+--------+--------+--------+--------+
+    /// |    Active |            3 |      1 |      2 |      1 |      - |
+    /// |       DFU |            3 |      3 |      1 |      2 |      3 |
+    /// +-----------+--------------+--------+--------+--------+--------+
+    ///
+    ///
+    /// +-----------+--------------+--------+--------+--------+--------+
+    /// | Partition | Revert Index | Page 0 | Page 1 | Page 3 | Page 4 |
+    /// +-----------+--------------+--------+--------+--------+--------+
+    /// |    Active |            3 |      1 |      2 |      1 |      - |
+    /// |       DFU |            3 |      3 |      2 |      2 |      3 |
+    /// +-----------+--------------+--------+--------+--------+--------+
+    ///
+    /// +-----------+--------------+--------+--------+--------+--------+
+    /// | Partition | Revert Index | Page 0 | Page 1 | Page 3 | Page 4 |
+    /// +-----------+--------------+--------+--------+--------+--------+
+    /// |    Active |            3 |      1 |      2 |      3 |      - |
+    /// |       DFU |            3 |      3 |      2 |      1 |      3 |
+    /// +-----------+--------------+--------+--------+--------+--------+
+    ///
+    pub fn prepare_boot<F: NorFlash + ReadNorFlash>(
+        &mut self,
+        flash: &mut F,
+    ) -> Result<State, BootError<F::Error>> {
+        // Copy contents from partition N to active
+        let state = self.read_state(flash)?;
+        match state {
+            State::Swap => {
+                //
+                // Check if we already swapped. If we're in the swap state, this means we should revert
+                // since the app has failed to mark boot as successful
+                //
+                if !self.is_swapped(flash)? {
+                    trace!("Swapping");
+                    self.swap(flash)?;
+                } else {
+                    trace!("Reverting");
+                    self.revert(flash)?;
+
+                    // Overwrite magic and reset progress
+                    flash.write(self.state.from as u32, &[0, 0, 0, 0])?;
+                    flash.erase(self.state.from as u32, self.state.to as u32)?;
+                    flash.write(self.state.from as u32, &BOOT_MAGIC.to_le_bytes())?;
+                }
+            }
+            _ => {}
+        }
+        Ok(state)
+    }
+
+    fn is_swapped<F: ReadNorFlash>(&mut self, flash: &mut F) -> Result<bool, F::Error> {
+        let page_count = self.active.len() / PAGE_SIZE;
+        let progress = self.current_progress(flash)?;
+
+        Ok(progress >= page_count * 2)
+    }
+
+    fn current_progress<F: ReadNorFlash>(&mut self, flash: &mut F) -> Result<usize, F::Error> {
+        let max_index = ((self.state.len() - 4) / 4) - 1;
+        for i in 0..max_index {
+            let mut buf: [u8; 4] = [0; 4];
+            flash.read((self.state.from + 4 + i * 4) as u32, &mut buf)?;
+            if buf == [0xFF, 0xFF, 0xFF, 0xFF] {
+                return Ok(i);
+            }
+        }
+        Ok(max_index)
+    }
+
+    fn update_progress<F: NorFlash>(&mut self, idx: usize, flash: &mut F) -> Result<(), F::Error> {
+        let w = self.state.from + 4 + idx * 4;
+        flash.write(w as u32, &[0, 0, 0, 0])?;
+        Ok(())
+    }
+
+    fn active_addr(&self, n: usize) -> usize {
+        self.active.from + n * PAGE_SIZE
+    }
+
+    fn dfu_addr(&self, n: usize) -> usize {
+        self.dfu.from + n * PAGE_SIZE
+    }
+
+    fn copy_page_once<F: NorFlash + ReadNorFlash>(
+        &mut self,
+        idx: usize,
+        from: usize,
+        to: usize,
+        flash: &mut F,
+    ) -> Result<(), F::Error> {
+        let mut buf: [u8; PAGE_SIZE] = [0; PAGE_SIZE];
+        if self.current_progress(flash)? <= idx {
+            flash.read(from as u32, &mut buf)?;
+            flash.erase(to as u32, (to + PAGE_SIZE) as u32)?;
+            flash.write(to as u32, &buf)?;
+            self.update_progress(idx, flash)?;
+        }
+        Ok(())
+    }
+
+    fn swap<F: NorFlash + ReadNorFlash>(&mut self, flash: &mut F) -> Result<(), F::Error> {
+        let page_count = self.active.len() / PAGE_SIZE;
+        // trace!("Page count: {}", page_count);
+        for page in 0..page_count {
+            // Copy active page to the 'next' DFU page.
+            let active_page = self.active_addr(page_count - 1 - page);
+            let dfu_page = self.dfu_addr(page_count - page);
+            // info!("Copy active {} to dfu {}", active_page, dfu_page);
+            self.copy_page_once(page * 2, active_page, dfu_page, flash)?;
+
+            // Copy DFU page to the active page
+            let active_page = self.active_addr(page_count - 1 - page);
+            let dfu_page = self.dfu_addr(page_count - 1 - page);
+            //info!("Copy dfy {} to active {}", dfu_page, active_page);
+            self.copy_page_once(page * 2 + 1, dfu_page, active_page, flash)?;
+        }
+
+        Ok(())
+    }
+
+    fn revert<F: NorFlash + ReadNorFlash>(&mut self, flash: &mut F) -> Result<(), F::Error> {
+        let page_count = self.active.len() / PAGE_SIZE;
+        for page in 0..page_count {
+            // Copy the bad active page to the DFU page
+            let active_page = self.active_addr(page);
+            let dfu_page = self.dfu_addr(page);
+            self.copy_page_once(page_count * 2 + page * 2, active_page, dfu_page, flash)?;
+
+            // Copy the DFU page back to the active page
+            let active_page = self.active_addr(page);
+            let dfu_page = self.dfu_addr(page + 1);
+            self.copy_page_once(page_count * 2 + page * 2 + 1, dfu_page, active_page, flash)?;
+        }
+
+        Ok(())
+    }
+
+    fn read_state<F: ReadNorFlash>(&mut self, flash: &mut F) -> Result<State, BootError<F::Error>> {
+        let mut magic: [u8; 4] = [0; 4];
+        flash.read(self.state.from as u32, &mut magic)?;
+
+        match u32::from_le_bytes(magic) {
+            SWAP_MAGIC => Ok(State::Swap),
+            _ => Ok(State::Boot),
+        }
+    }
+}
+
+/// FirmwareUpdater is an application API for interacting with the BootLoader without the ability to
+/// 'mess up' the internal bootloader state
+pub struct FirmwareUpdater {
+    state: Partition,
+    dfu: Partition,
+}
+
+impl FirmwareUpdater {
+    pub const fn new(dfu: Partition, state: Partition) -> Self {
+        Self { dfu, state }
+    }
+
+    /// Return the length of the DFU area
+    pub fn firmware_len(&self) -> usize {
+        self.dfu.len()
+    }
+
+    /// Instruct bootloader that DFU should commence at next boot.
+    pub async fn mark_update<F: AsyncNorFlash>(&mut self, flash: &mut F) -> Result<(), F::Error> {
+        flash.write(self.state.from as u32, &[0, 0, 0, 0]).await?;
+        flash
+            .erase(self.state.from as u32, self.state.to as u32)
+            .await?;
+        info!(
+            "Setting swap magic at {} to 0x{:x}, LE: 0x{:x}",
+            self.state.from,
+            &SWAP_MAGIC,
+            &SWAP_MAGIC.to_le_bytes()
+        );
+        flash
+            .write(self.state.from as u32, &SWAP_MAGIC.to_le_bytes())
+            .await?;
+        Ok(())
+    }
+
+    /// Mark firmware boot successfully
+    pub async fn mark_booted<F: AsyncNorFlash>(&mut self, flash: &mut F) -> Result<(), F::Error> {
+        flash.write(self.state.from as u32, &[0, 0, 0, 0]).await?;
+        flash
+            .erase(self.state.from as u32, self.state.to as u32)
+            .await?;
+        flash
+            .write(self.state.from as u32, &BOOT_MAGIC.to_le_bytes())
+            .await?;
+        Ok(())
+    }
+
+    // Write to a region of the DFU page
+    pub async fn write_firmware<F: AsyncNorFlash>(
+        &mut self,
+        offset: usize,
+        data: &[u8],
+        flash: &mut F,
+    ) -> Result<(), F::Error> {
+        info!(
+            "Writing firmware at offset 0x{:x} len {}",
+            self.dfu.from + offset,
+            data.len()
+        );
+
+        flash
+            .erase(
+                (self.dfu.from + offset) as u32,
+                (self.dfu.from + offset + data.len()) as u32,
+            )
+            .await?;
+        flash.write((self.dfu.from + offset) as u32, data).await
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use core::convert::Infallible;
+    use core::future::Future;
+    use embedded_storage_async::nor_flash::AsyncReadNorFlash;
+    use futures::executor::block_on;
+
+    const STATE: Partition = Partition::new(0, 4096);
+    const ACTIVE: Partition = Partition::new(4096, 61440);
+    const DFU: Partition = Partition::new(61440, 122880);
+
+    #[test]
+    fn test_bad_magic() {
+        let mut flash = MemFlash([0xff; 131072]);
+
+        let mut bootloader = BootLoader::<4096>::new(ACTIVE, DFU, STATE);
+
+        assert_eq!(
+            bootloader.prepare_boot(&mut flash),
+            Err(BootError::BadMagic)
+        );
+    }
+
+    #[test]
+    fn test_boot_state() {
+        let mut flash = MemFlash([0xff; 131072]);
+        flash.0[0..4].copy_from_slice(&BOOT_MAGIC.to_le_bytes());
+
+        let mut bootloader = BootLoader::<4096>::new(ACTIVE, DFU, STATE);
+
+        assert_eq!(State::Boot, bootloader.prepare_boot(&mut flash).unwrap());
+    }
+
+    #[test]
+    fn test_swap_state() {
+        env_logger::init();
+        let mut flash = MemFlash([0xff; 131072]);
+
+        let original: [u8; ACTIVE.len()] = [rand::random::<u8>(); ACTIVE.len()];
+        let update: [u8; DFU.len()] = [rand::random::<u8>(); DFU.len()];
+
+        for i in ACTIVE.from..ACTIVE.to {
+            flash.0[i] = original[i - ACTIVE.from];
+        }
+
+        let mut bootloader = BootLoader::<4096>::new(ACTIVE, DFU, STATE);
+        let mut updater = FirmwareUpdater::new(DFU, STATE);
+        for i in (DFU.from..DFU.to).step_by(4) {
+            let base = i - DFU.from;
+            let data: [u8; 4] = [
+                update[base],
+                update[base + 1],
+                update[base + 2],
+                update[base + 3],
+            ];
+            block_on(updater.write_firmware(i - DFU.from, &data, &mut flash)).unwrap();
+        }
+        block_on(updater.mark_update(&mut flash)).unwrap();
+
+        assert_eq!(State::Swap, bootloader.prepare_boot(&mut flash).unwrap());
+
+        for i in ACTIVE.from..ACTIVE.to {
+            assert_eq!(flash.0[i], update[i - ACTIVE.from], "Index {}", i);
+        }
+
+        // First DFU page is untouched
+        for i in DFU.from + 4096..DFU.to {
+            assert_eq!(flash.0[i], original[i - DFU.from - 4096], "Index {}", i);
+        }
+
+        // Running again should cause a revert
+        assert_eq!(State::Swap, bootloader.prepare_boot(&mut flash).unwrap());
+
+        for i in ACTIVE.from..ACTIVE.to {
+            assert_eq!(flash.0[i], original[i - ACTIVE.from], "Index {}", i);
+        }
+
+        // Last page is untouched
+        for i in DFU.from..DFU.to - 4096 {
+            assert_eq!(flash.0[i], update[i - DFU.from], "Index {}", i);
+        }
+
+        // Mark as booted
+        block_on(updater.mark_booted(&mut flash)).unwrap();
+        assert_eq!(State::Boot, bootloader.prepare_boot(&mut flash).unwrap());
+    }
+
+    struct MemFlash([u8; 131072]);
+
+    impl NorFlash for MemFlash {
+        const WRITE_SIZE: usize = 4;
+        const ERASE_SIZE: usize = 4096;
+        fn erase(&mut self, from: u32, to: u32) -> Result<(), Self::Error> {
+            let from = from as usize;
+            let to = to as usize;
+            for i in from..to {
+                self.0[i] = 0xFF;
+                self.0[i] = 0xFF;
+                self.0[i] = 0xFF;
+                self.0[i] = 0xFF;
+            }
+            Ok(())
+        }
+
+        fn write(&mut self, offset: u32, data: &[u8]) -> Result<(), Self::Error> {
+            assert!(data.len() % 4 == 0);
+            assert!(offset % 4 == 0);
+            assert!(offset as usize + data.len() < 131072);
+
+            self.0[offset as usize..offset as usize + data.len()].copy_from_slice(data);
+
+            Ok(())
+        }
+    }
+
+    impl ReadNorFlash for MemFlash {
+        const READ_SIZE: usize = 4;
+        type Error = Infallible;
+
+        fn read(&mut self, offset: u32, buf: &mut [u8]) -> Result<(), Self::Error> {
+            let len = buf.len();
+            buf[..].copy_from_slice(&self.0[offset as usize..offset as usize + len]);
+            Ok(())
+        }
+
+        fn capacity(&self) -> usize {
+            131072
+        }
+    }
+
+    impl AsyncReadNorFlash for MemFlash {
+        const READ_SIZE: usize = 4;
+        type Error = Infallible;
+
+        type ReadFuture<'a> = impl Future<Output = Result<(), Self::Error>> + 'a;
+        fn read<'a>(&'a mut self, offset: usize, buf: &'a mut [u8]) -> Self::ReadFuture<'a> {
+            async move {
+                let len = buf.len();
+                buf[..].copy_from_slice(&self.0[offset as usize..offset as usize + len]);
+                Ok(())
+            }
+        }
+
+        fn capacity(&self) -> usize {
+            131072
+        }
+    }
+
+    impl AsyncNorFlash for MemFlash {
+        const WRITE_SIZE: usize = 4;
+        const ERASE_SIZE: usize = 4096;
+
+        type EraseFuture<'a> = impl Future<Output = Result<(), Self::Error>> + 'a;
+        fn erase<'a>(&'a mut self, from: u32, to: u32) -> Self::EraseFuture<'a> {
+            async move {
+                let from = from as usize;
+                let to = to as usize;
+                for i in from..to {
+                    self.0[i] = 0xFF;
+                    self.0[i] = 0xFF;
+                    self.0[i] = 0xFF;
+                    self.0[i] = 0xFF;
+                }
+                Ok(())
+            }
+        }
+
+        type WriteFuture<'a> = impl Future<Output = Result<(), Self::Error>> + 'a;
+        fn write<'a>(&'a mut self, offset: u32, data: &'a [u8]) -> Self::WriteFuture<'a> {
+            async move {
+                assert!(data.len() % 4 == 0);
+                assert!(offset % 4 == 0);
+                assert!(offset as usize + data.len() < 131072);
+
+                self.0[offset as usize..offset as usize + data.len()].copy_from_slice(data);
+
+                Ok(())
+            }
+        }
+    }
+}
diff --git a/embassy-boot/nrf/.cargo/config.toml b/embassy-boot/nrf/.cargo/config.toml
new file mode 100644
index 000000000..c3957b866
--- /dev/null
+++ b/embassy-boot/nrf/.cargo/config.toml
@@ -0,0 +1,18 @@
+[unstable]
+namespaced-features = true
+build-std = ["core"]
+build-std-features = ["panic_immediate_abort"]
+
+[target.'cfg(all(target_arch = "arm", target_os = "none"))']
+#runner = "./fruitrunner"
+runner = "probe-run --chip nrf52840_xxAA"
+
+rustflags = [
+  # Code-size optimizations.
+  "-Z", "trap-unreachable=no",
+  #"-C", "no-vectorize-loops",
+  "-C", "force-frame-pointers=yes",
+]
+
+[build]
+target = "thumbv7em-none-eabi"
diff --git a/embassy-boot/nrf/Cargo.toml b/embassy-boot/nrf/Cargo.toml
new file mode 100644
index 000000000..512e7d378
--- /dev/null
+++ b/embassy-boot/nrf/Cargo.toml
@@ -0,0 +1,65 @@
+[package]
+authors = [
+    "Ulf Lilleengen <[email protected]>",
+]
+edition = "2018"
+name = "embassy-boot-nrf"
+version = "0.1.0"
+description = "Bootloader for nRF chips"
+
+[dependencies]
+defmt = { version = "0.3", optional = true }
+defmt-rtt = { version = "0.3", optional = true }
+
+embassy = { path = "../../embassy", default-features = false }
+embassy-nrf = { path = "../../embassy-nrf", default-features = false }
+embassy-boot = { path = "../boot", default-features = false }
+cortex-m = { version = "0.7" }
+cortex-m-rt = { version = "0.7" }
+embedded-storage = "0.3.0"
+embedded-storage-async = "0.3.0"
+cfg-if = "1.0.0"
+
+nrf-softdevice-mbr = { version = "0.1.0", git = "https://github.com/embassy-rs/nrf-softdevice.git", branch = "master", optional = true }
+
+[features]
+defmt = [
+    "dep:defmt",
+    "embassy-boot/defmt",
+    "embassy-nrf/defmt",
+]
+softdevice = [
+    "nrf-softdevice-mbr",
+]
+debug = ["defmt-rtt"]
+
+[profile.dev]
+debug = 2
+debug-assertions = true
+incremental = false
+opt-level = 'z'
+overflow-checks = true
+
+[profile.release]
+codegen-units = 1
+debug = 2
+debug-assertions = false
+incremental = false
+lto = 'fat'
+opt-level = 'z'
+overflow-checks = false
+
+# do not optimize proc-macro crates = faster builds from scratch
+[profile.dev.build-override]
+codegen-units = 8
+debug = false
+debug-assertions = false
+opt-level = 0
+overflow-checks = false
+
+[profile.release.build-override]
+codegen-units = 8
+debug = false
+debug-assertions = false
+opt-level = 0
+overflow-checks = false
diff --git a/embassy-boot/nrf/README.md b/embassy-boot/nrf/README.md
new file mode 100644
index 000000000..23497a038
--- /dev/null
+++ b/embassy-boot/nrf/README.md
@@ -0,0 +1,11 @@
+# Bootloader for nRF
+
+The bootloader uses `embassy-boot` to interact with the flash.
+
+# Usage
+
+Flash the bootloader
+
+```
+cargo flash --features embassy-nrf/nrf52832 --release --chip nRF52832_xxAA
+```
diff --git a/embassy-boot/nrf/build.rs b/embassy-boot/nrf/build.rs
new file mode 100644
index 000000000..e1da69328
--- /dev/null
+++ b/embassy-boot/nrf/build.rs
@@ -0,0 +1,37 @@
+//! This build script copies the `memory.x` file from the crate root into
+//! a directory where the linker can always find it at build time.
+//! For many projects this is optional, as the linker always searches the
+//! project root directory -- wherever `Cargo.toml` is. However, if you
+//! are using a workspace or have a more complicated build setup, this
+//! build script becomes required. Additionally, by requesting that
+//! Cargo re-run the build script whenever `memory.x` is changed,
+//! updating `memory.x` ensures a rebuild of the application with the
+//! new memory settings.
+
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::PathBuf;
+
+fn main() {
+    // Put `memory.x` in our output directory and ensure it's
+    // on the linker search path.
+    let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    File::create(out.join("memory.x"))
+        .unwrap()
+        .write_all(include_bytes!("memory.x"))
+        .unwrap();
+    println!("cargo:rustc-link-search={}", out.display());
+
+    // By default, Cargo will re-run a build script whenever
+    // any file in the project changes. By specifying `memory.x`
+    // here, we ensure the build script is only re-run when
+    // `memory.x` is changed.
+    println!("cargo:rerun-if-changed=memory.x");
+
+    println!("cargo:rustc-link-arg-bins=--nmagic");
+    println!("cargo:rustc-link-arg-bins=-Tlink.x");
+    if env::var("CARGO_FEATURE_DEFMT").is_ok() {
+        println!("cargo:rustc-link-arg-bins=-Tdefmt.x");
+    }
+}
diff --git a/embassy-boot/nrf/memory-bm.x b/embassy-boot/nrf/memory-bm.x
new file mode 100644
index 000000000..257d65644
--- /dev/null
+++ b/embassy-boot/nrf/memory-bm.x
@@ -0,0 +1,18 @@
+MEMORY
+{
+  /* NOTE 1 K = 1 KiBi = 1024 bytes */
+  FLASH                             : ORIGIN = 0x00000000, LENGTH = 24K
+  BOOTLOADER_STATE                  : ORIGIN = 0x00006000, LENGTH = 4K
+  ACTIVE                            : ORIGIN = 0x00007000, LENGTH = 64K
+  DFU                               : ORIGIN = 0x00017000, LENGTH = 68K
+  RAM                         (rwx) : ORIGIN = 0x20000000, LENGTH = 32K
+}
+
+__bootloader_state_start = ORIGIN(BOOTLOADER_STATE);
+__bootloader_state_end = ORIGIN(BOOTLOADER_STATE) + LENGTH(BOOTLOADER_STATE);
+
+__bootloader_active_start = ORIGIN(ACTIVE);
+__bootloader_active_end = ORIGIN(ACTIVE) + LENGTH(ACTIVE);
+
+__bootloader_dfu_start = ORIGIN(DFU);
+__bootloader_dfu_end = ORIGIN(DFU) + LENGTH(DFU);
diff --git a/embassy-boot/nrf/memory-s140.x b/embassy-boot/nrf/memory-s140.x
new file mode 100644
index 000000000..105db9972
--- /dev/null
+++ b/embassy-boot/nrf/memory-s140.x
@@ -0,0 +1,31 @@
+MEMORY
+{
+  /* NOTE 1 K = 1 KiBi = 1024 bytes */
+  MBR                               : ORIGIN = 0x00000000, LENGTH = 4K
+  SOFTDEVICE                        : ORIGIN = 0x00001000, LENGTH = 155648
+  ACTIVE                            : ORIGIN = 0x00027000, LENGTH = 425984
+  DFU                               : ORIGIN = 0x0008F000, LENGTH = 430080
+  FLASH                             : ORIGIN = 0x000f9000, LENGTH = 24K
+  BOOTLOADER_STATE                  : ORIGIN = 0x000ff000, LENGTH = 4K
+  RAM                         (rwx) : ORIGIN = 0x20000008, LENGTH = 0x2fff8
+  uicr_bootloader_start_address (r) : ORIGIN = 0x10001014, LENGTH = 0x4
+}
+
+__bootloader_state_start = ORIGIN(BOOTLOADER_STATE);
+__bootloader_state_end = ORIGIN(BOOTLOADER_STATE) + LENGTH(BOOTLOADER_STATE);
+
+__bootloader_active_start = ORIGIN(ACTIVE);
+__bootloader_active_end = ORIGIN(ACTIVE) + LENGTH(ACTIVE);
+
+__bootloader_dfu_start = ORIGIN(DFU);
+__bootloader_dfu_end = ORIGIN(DFU) + LENGTH(DFU);
+
+__bootloader_start = ORIGIN(FLASH);
+
+SECTIONS
+{
+  .uicr_bootloader_start_address :
+  {
+    LONG(__bootloader_start)
+  } > uicr_bootloader_start_address
+}
diff --git a/embassy-boot/nrf/memory.x b/embassy-boot/nrf/memory.x
new file mode 100644
index 000000000..257d65644
--- /dev/null
+++ b/embassy-boot/nrf/memory.x
@@ -0,0 +1,18 @@
+MEMORY
+{
+  /* NOTE 1 K = 1 KiBi = 1024 bytes */
+  FLASH                             : ORIGIN = 0x00000000, LENGTH = 24K
+  BOOTLOADER_STATE                  : ORIGIN = 0x00006000, LENGTH = 4K
+  ACTIVE                            : ORIGIN = 0x00007000, LENGTH = 64K
+  DFU                               : ORIGIN = 0x00017000, LENGTH = 68K
+  RAM                         (rwx) : ORIGIN = 0x20000000, LENGTH = 32K
+}
+
+__bootloader_state_start = ORIGIN(BOOTLOADER_STATE);
+__bootloader_state_end = ORIGIN(BOOTLOADER_STATE) + LENGTH(BOOTLOADER_STATE);
+
+__bootloader_active_start = ORIGIN(ACTIVE);
+__bootloader_active_end = ORIGIN(ACTIVE) + LENGTH(ACTIVE);
+
+__bootloader_dfu_start = ORIGIN(DFU);
+__bootloader_dfu_end = ORIGIN(DFU) + LENGTH(DFU);
diff --git a/embassy-boot/nrf/src/fmt.rs b/embassy-boot/nrf/src/fmt.rs
new file mode 100644
index 000000000..066970813
--- /dev/null
+++ b/embassy-boot/nrf/src/fmt.rs
@@ -0,0 +1,225 @@
+#![macro_use]
+#![allow(unused_macros)]
+
+#[cfg(all(feature = "defmt", feature = "log"))]
+compile_error!("You may not enable both `defmt` and `log` features.");
+
+macro_rules! assert {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert!($($x)*);
+        }
+    };
+}
+
+macro_rules! assert_eq {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert_eq!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert_eq!($($x)*);
+        }
+    };
+}
+
+macro_rules! assert_ne {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert_ne!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert_ne!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert_eq {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert_eq!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert_eq!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert_ne {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert_ne!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert_ne!($($x)*);
+        }
+    };
+}
+
+macro_rules! todo {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::todo!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::todo!($($x)*);
+        }
+    };
+}
+
+macro_rules! unreachable {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::unreachable!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::unreachable!($($x)*);
+        }
+    };
+}
+
+macro_rules! panic {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::panic!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::panic!($($x)*);
+        }
+    };
+}
+
+macro_rules! trace {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::trace!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::trace!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! debug {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::debug!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! info {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::info!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::info!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! warn {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::warn!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::warn!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! error {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::error!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::error!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+#[cfg(feature = "defmt")]
+macro_rules! unwrap {
+    ($($x:tt)*) => {
+        ::defmt::unwrap!($($x)*)
+    };
+}
+
+#[cfg(not(feature = "defmt"))]
+macro_rules! unwrap {
+    ($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-boot/nrf/src/lib.rs b/embassy-boot/nrf/src/lib.rs
new file mode 100644
index 000000000..af7ec7da2
--- /dev/null
+++ b/embassy-boot/nrf/src/lib.rs
@@ -0,0 +1,203 @@
+#![no_std]
+#![feature(generic_associated_types)]
+#![feature(type_alias_impl_trait)]
+
+mod fmt;
+
+pub use embassy_boot::{FirmwareUpdater, Partition, State, BOOT_MAGIC};
+use embassy_nrf::{
+    nvmc::{Nvmc, PAGE_SIZE},
+    peripherals::WDT,
+    wdt,
+};
+use embedded_storage::nor_flash::{ErrorType, NorFlash, ReadNorFlash};
+
+pub struct BootLoader {
+    boot: embassy_boot::BootLoader<PAGE_SIZE>,
+}
+
+impl BootLoader {
+    /// Create a new bootloader instance using parameters from linker script
+    pub fn default() -> Self {
+        extern "C" {
+            static __bootloader_state_start: u32;
+            static __bootloader_state_end: u32;
+            static __bootloader_active_start: u32;
+            static __bootloader_active_end: u32;
+            static __bootloader_dfu_start: u32;
+            static __bootloader_dfu_end: u32;
+        }
+
+        let active = unsafe {
+            Partition::new(
+                &__bootloader_active_start as *const u32 as usize,
+                &__bootloader_active_end as *const u32 as usize,
+            )
+        };
+        let dfu = unsafe {
+            Partition::new(
+                &__bootloader_dfu_start as *const u32 as usize,
+                &__bootloader_dfu_end as *const u32 as usize,
+            )
+        };
+        let state = unsafe {
+            Partition::new(
+                &__bootloader_state_start as *const u32 as usize,
+                &__bootloader_state_end as *const u32 as usize,
+            )
+        };
+
+        trace!("ACTIVE: 0x{:x} - 0x{:x}", active.from, active.to);
+        trace!("DFU: 0x{:x} - 0x{:x}", dfu.from, dfu.to);
+        trace!("STATE: 0x{:x} - 0x{:x}", state.from, state.to);
+
+        Self::new(active, dfu, state)
+    }
+
+    /// Create a new bootloader instance using the supplied partitions for active, dfu and state.
+    pub fn new(active: Partition, dfu: Partition, state: Partition) -> Self {
+        Self {
+            boot: embassy_boot::BootLoader::new(active, dfu, state),
+        }
+    }
+
+    /// Boots the application without softdevice mechanisms
+    pub fn prepare<F: NorFlash + ReadNorFlash>(&mut self, flash: &mut F) -> usize {
+        match self.boot.prepare_boot(flash) {
+            Ok(_) => self.boot.boot_address(),
+            Err(_) => panic!("boot prepare error!"),
+        }
+    }
+
+    #[cfg(not(feature = "softdevice"))]
+    pub unsafe fn load(&mut self, start: usize) -> ! {
+        let mut p = cortex_m::Peripherals::steal();
+        p.SCB.invalidate_icache();
+        p.SCB.vtor.write(start as u32);
+        cortex_m::asm::bootload(start as *const u32)
+    }
+
+    #[cfg(feature = "softdevice")]
+    pub unsafe fn load(&mut self, _app: usize) -> ! {
+        use nrf_softdevice_mbr as mbr;
+        const NRF_SUCCESS: u32 = 0;
+
+        // Address of softdevice which we'll forward interrupts to
+        let addr = 0x1000;
+        let mut cmd = mbr::sd_mbr_command_t {
+            command: mbr::NRF_MBR_COMMANDS_SD_MBR_COMMAND_IRQ_FORWARD_ADDRESS_SET,
+            params: mbr::sd_mbr_command_t__bindgen_ty_1 {
+                irq_forward_address_set: mbr::sd_mbr_command_irq_forward_address_set_t {
+                    address: addr,
+                },
+            },
+        };
+        let ret = mbr::sd_mbr_command(&mut cmd);
+        assert_eq!(ret, NRF_SUCCESS);
+
+        let msp = *(addr as *const u32);
+        let rv = *((addr + 4) as *const u32);
+
+        trace!("msp = {=u32:x}, rv = {=u32:x}", msp, rv);
+
+        core::arch::asm!(
+            "mrs {tmp}, CONTROL",
+            "bics {tmp}, {spsel}",
+            "msr CONTROL, {tmp}",
+            "isb",
+            "msr MSP, {msp}",
+            "mov lr, {new_lr}",
+            "bx {rv}",
+            // `out(reg) _` is not permitted in a `noreturn` asm! call,
+            // so instead use `in(reg) 0` and don't restore it afterwards.
+            tmp = in(reg) 0,
+            spsel = in(reg) 2,
+            new_lr = in(reg) 0xFFFFFFFFu32,
+            msp = in(reg) msp,
+            rv = in(reg) rv,
+            options(noreturn),
+        );
+    }
+}
+
+/// A flash implementation that wraps NVMC and will pet a watchdog when touching flash.
+pub struct WatchdogFlash<'d> {
+    flash: Nvmc<'d>,
+    wdt: wdt::WatchdogHandle,
+}
+
+impl<'d> WatchdogFlash<'d> {
+    /// Start a new watchdog with a given flash and WDT peripheral and a timeout
+    pub fn start(flash: Nvmc<'d>, wdt: WDT, timeout: u32) -> Self {
+        let mut config = wdt::Config::default();
+        config.timeout_ticks = 32768 * timeout; // timeout seconds
+        config.run_during_sleep = true;
+        config.run_during_debug_halt = false;
+        let (_wdt, [wdt]) = match wdt::Watchdog::try_new(wdt, config) {
+            Ok(x) => x,
+            Err(_) => {
+                // In case the watchdog is already running, just spin and let it expire, since
+                // we can't configure it anyway. This usually happens when we first program
+                // the device and the watchdog was previously active
+                info!("Watchdog already active with wrong config, waiting for it to timeout...");
+                loop {}
+            }
+        };
+        Self { flash, wdt }
+    }
+}
+
+impl<'d> ErrorType for WatchdogFlash<'d> {
+    type Error = <Nvmc<'d> as ErrorType>::Error;
+}
+
+impl<'d> NorFlash for WatchdogFlash<'d> {
+    const WRITE_SIZE: usize = <Nvmc<'d> as NorFlash>::WRITE_SIZE;
+    const ERASE_SIZE: usize = <Nvmc<'d> as NorFlash>::ERASE_SIZE;
+
+    fn erase(&mut self, from: u32, to: u32) -> Result<(), Self::Error> {
+        self.wdt.pet();
+        self.flash.erase(from, to)
+    }
+    fn write(&mut self, offset: u32, data: &[u8]) -> Result<(), Self::Error> {
+        self.wdt.pet();
+        self.flash.write(offset, data)
+    }
+}
+
+impl<'d> ReadNorFlash for WatchdogFlash<'d> {
+    const READ_SIZE: usize = <Nvmc<'d> as ReadNorFlash>::READ_SIZE;
+    fn read(&mut self, offset: u32, data: &mut [u8]) -> Result<(), Self::Error> {
+        self.wdt.pet();
+        self.flash.read(offset, data)
+    }
+    fn capacity(&self) -> usize {
+        self.flash.capacity()
+    }
+}
+
+pub mod updater {
+    use super::*;
+    pub fn new() -> embassy_boot::FirmwareUpdater {
+        extern "C" {
+            static __bootloader_state_start: u32;
+            static __bootloader_state_end: u32;
+            static __bootloader_dfu_start: u32;
+            static __bootloader_dfu_end: u32;
+        }
+
+        let dfu = unsafe {
+            Partition::new(
+                &__bootloader_dfu_start as *const u32 as usize,
+                &__bootloader_dfu_end as *const u32 as usize,
+            )
+        };
+        let state = unsafe {
+            Partition::new(
+                &__bootloader_state_start as *const u32 as usize,
+                &__bootloader_state_end as *const u32 as usize,
+            )
+        };
+        embassy_boot::FirmwareUpdater::new(dfu, state)
+    }
+}
diff --git a/embassy-boot/nrf/src/main.rs b/embassy-boot/nrf/src/main.rs
new file mode 100644
index 000000000..08b854a7e
--- /dev/null
+++ b/embassy-boot/nrf/src/main.rs
@@ -0,0 +1,46 @@
+#![no_std]
+#![no_main]
+
+use cortex_m_rt::{entry, exception};
+
+#[cfg(feature = "defmt")]
+use defmt_rtt as _;
+
+use embassy_boot_nrf::*;
+use embassy_nrf::nvmc::Nvmc;
+
+#[entry]
+fn main() -> ! {
+    let p = embassy_nrf::init(Default::default());
+    /*
+        for i in 0..10000000 {
+            cortex_m::asm::nop();
+        }
+    */
+
+    let mut bl = BootLoader::default();
+    let start = bl.prepare(&mut WatchdogFlash::start(Nvmc::new(p.NVMC), p.WDT, 5));
+    unsafe { bl.load(start) }
+}
+
+#[no_mangle]
+#[cfg_attr(target_os = "none", link_section = ".HardFault.user")]
+unsafe extern "C" fn HardFault() {
+    cortex_m::peripheral::SCB::sys_reset();
+}
+
+#[exception]
+unsafe fn DefaultHandler(_: i16) -> ! {
+    const SCB_ICSR: *const u32 = 0xE000_ED04 as *const u32;
+    let irqn = core::ptr::read_volatile(SCB_ICSR) as u8 as i16 - 16;
+
+    panic!("DefaultHandler #{:?}", irqn);
+}
+
+#[panic_handler]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
+    unsafe {
+        core::arch::asm!("udf #0");
+        core::hint::unreachable_unchecked();
+    }
+}
diff --git a/embassy-traits/Cargo.toml b/embassy-traits/Cargo.toml
index 39875687f..fa2082ef3 100644
--- a/embassy-traits/Cargo.toml
+++ b/embassy-traits/Cargo.toml
@@ -11,4 +11,6 @@ std = []
 embedded-hal-02 = { package = "embedded-hal", version = "0.2.6", features = ["unproven"] }
 embedded-hal-1 = { package = "embedded-hal", version = "1.0.0-alpha.6", git = "https://github.com/embassy-rs/embedded-hal", branch = "embassy" }
 embedded-hal-async = { version = "0.0.1", git = "https://github.com/embassy-rs/embedded-hal", branch = "embassy"}
+embedded-storage = "0.3.0"
+embedded-storage-async = "0.3.0"
 nb = "1.0.0"
diff --git a/embassy-traits/src/adapter.rs b/embassy-traits/src/adapter.rs
index 415b5e814..735f9aacc 100644
--- a/embassy-traits/src/adapter.rs
+++ b/embassy-traits/src/adapter.rs
@@ -254,3 +254,56 @@ where
         async move { self.wrapped.bflush() }
     }
 }
+
+/// NOR flash wrapper
+use embedded_storage::nor_flash::{ErrorType, NorFlash, ReadNorFlash};
+use embedded_storage_async::nor_flash::{AsyncNorFlash, AsyncReadNorFlash};
+
+impl<T> ErrorType for BlockingAsync<T>
+where
+    T: ErrorType,
+{
+    type Error = T::Error;
+}
+
+impl<T> AsyncNorFlash for BlockingAsync<T>
+where
+    T: NorFlash,
+{
+    const WRITE_SIZE: usize = <T as NorFlash>::WRITE_SIZE;
+    const ERASE_SIZE: usize = <T as NorFlash>::ERASE_SIZE;
+
+    type WriteFuture<'a>
+    where
+        Self: 'a,
+    = impl Future<Output = Result<(), Self::Error>> + 'a;
+    fn write<'a>(&'a mut self, offset: u32, data: &'a [u8]) -> Self::WriteFuture<'a> {
+        async move { self.wrapped.write(offset, data) }
+    }
+
+    type EraseFuture<'a>
+    where
+        Self: 'a,
+    = impl Future<Output = Result<(), Self::Error>> + 'a;
+    fn erase<'a>(&'a mut self, from: u32, to: u32) -> Self::EraseFuture<'a> {
+        async move { self.wrapped.erase(from, to) }
+    }
+}
+
+impl<T> AsyncReadNorFlash for BlockingAsync<T>
+where
+    T: ReadNorFlash,
+{
+    const READ_SIZE: usize = <T as ReadNorFlash>::READ_SIZE;
+    type ReadFuture<'a>
+    where
+        Self: 'a,
+    = impl Future<Output = Result<(), Self::Error>> + 'a;
+    fn read<'a>(&'a mut self, address: u32, data: &'a mut [u8]) -> Self::ReadFuture<'a> {
+        async move { self.wrapped.read(address, data) }
+    }
+
+    fn capacity(&self) -> usize {
+        self.wrapped.capacity()
+    }
+}
diff --git a/examples/boot/.cargo/config.toml b/examples/boot/.cargo/config.toml
new file mode 100644
index 000000000..d044e9b4c
--- /dev/null
+++ b/examples/boot/.cargo/config.toml
@@ -0,0 +1,7 @@
+[unstable]
+namespaced-features = true
+build-std = ["core"]
+build-std-features = ["panic_immediate_abort"]
+
+[build]
+target = "thumbv7em-none-eabi"
diff --git a/examples/boot/Cargo.toml b/examples/boot/Cargo.toml
new file mode 100644
index 000000000..36e2e169d
--- /dev/null
+++ b/examples/boot/Cargo.toml
@@ -0,0 +1,19 @@
+[package]
+authors = ["Ulf Lilleengen <[email protected]>"]
+edition = "2018"
+name = "embassy-boot-examples"
+version = "0.1.0"
+
+[dependencies]
+embassy = { version = "0.1.0", path = "../../embassy" }
+embassy-nrf = { version = "0.1.0", path = "../../embassy-nrf", features = ["time-driver-rtc1", "gpiote"] }
+embassy-boot-nrf = { version = "0.1.0", path = "../../embassy-boot/nrf" }
+embassy-traits = { version = "0.1.0", path = "../../embassy-traits" }
+
+defmt = { version = "0.3", optional = true }
+defmt-rtt = { version = "0.3", optional = true }
+panic-reset = { version = "0.1.1" }
+embedded-hal = { version = "0.2.6" }
+
+cortex-m = "0.7.3"
+cortex-m-rt = "0.7.0"
diff --git a/examples/boot/README.md b/examples/boot/README.md
new file mode 100644
index 000000000..b97513a9d
--- /dev/null
+++ b/examples/boot/README.md
@@ -0,0 +1,31 @@
+# Examples using bootloader
+
+Example for nRF52 demonstrating the bootloader. The example consists of application binaries, 'a'
+which allows you to press a button to start the DFU process, and 'b' which is the updated
+application.
+
+
+## Prerequisites
+
+* `cargo-binutils`
+* `cargo-flash`
+* `embassy-boot-nrf`
+
+## Usage
+
+
+
+```
+# Flash bootloader
+cargo flash --manifest-path ../../embassy-boot/nrf/Cargo.toml --release --features embassy-nrf/nrf52840 --chip nRF52840_xxAA
+# Build 'b'
+cargo build --release --features embassy-nrf/nrf52840 --bin b
+# Generate binary for 'b'
+cargo objcopy --release --features embassy-nrf/nrf52840 --bin b -- -O binary b.bin
+```
+
+# Flash `a` (which includes b.bin)
+
+```
+cargo flash --release --features embassy-nrf/nrf52840 --bin a --chip nRF52840_xxAA
+```
diff --git a/examples/boot/build.rs b/examples/boot/build.rs
new file mode 100644
index 000000000..cd1a264c4
--- /dev/null
+++ b/examples/boot/build.rs
@@ -0,0 +1,34 @@
+//! This build script copies the `memory.x` file from the crate root into
+//! a directory where the linker can always find it at build time.
+//! For many projects this is optional, as the linker always searches the
+//! project root directory -- wherever `Cargo.toml` is. However, if you
+//! are using a workspace or have a more complicated build setup, this
+//! build script becomes required. Additionally, by requesting that
+//! Cargo re-run the build script whenever `memory.x` is changed,
+//! updating `memory.x` ensures a rebuild of the application with the
+//! new memory settings.
+
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::PathBuf;
+
+fn main() {
+    // Put `memory.x` in our output directory and ensure it's
+    // on the linker search path.
+    let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    File::create(out.join("memory.x"))
+        .unwrap()
+        .write_all(include_bytes!("memory.x"))
+        .unwrap();
+    println!("cargo:rustc-link-search={}", out.display());
+
+    // By default, Cargo will re-run a build script whenever
+    // any file in the project changes. By specifying `memory.x`
+    // here, we ensure the build script is only re-run when
+    // `memory.x` is changed.
+    println!("cargo:rerun-if-changed=memory.x");
+
+    println!("cargo:rustc-link-arg-bins=--nmagic");
+    println!("cargo:rustc-link-arg-bins=-Tlink.x");
+}
diff --git a/examples/boot/memory.x b/examples/boot/memory.x
new file mode 100644
index 000000000..dfb72103f
--- /dev/null
+++ b/examples/boot/memory.x
@@ -0,0 +1,14 @@
+MEMORY
+{
+  /* NOTE 1 K = 1 KiBi = 1024 bytes */
+  BOOTLOADER_STATE                  : ORIGIN = 0x00006000, LENGTH = 4K
+  FLASH                             : ORIGIN = 0x00007000, LENGTH = 64K
+  DFU                               : ORIGIN = 0x00017000, LENGTH = 68K
+  RAM                         (rwx) : ORIGIN = 0x20000000, LENGTH = 32K
+}
+
+__bootloader_state_start = ORIGIN(BOOTLOADER_STATE);
+__bootloader_state_end = ORIGIN(BOOTLOADER_STATE) + LENGTH(BOOTLOADER_STATE);
+
+__bootloader_dfu_start = ORIGIN(DFU);
+__bootloader_dfu_end = ORIGIN(DFU) + LENGTH(DFU);
diff --git a/examples/boot/src/bin/a.rs b/examples/boot/src/bin/a.rs
new file mode 100644
index 000000000..88880e688
--- /dev/null
+++ b/examples/boot/src/bin/a.rs
@@ -0,0 +1,49 @@
+#![no_std]
+#![no_main]
+#![macro_use]
+#![feature(generic_associated_types)]
+#![feature(type_alias_impl_trait)]
+
+use embassy_boot_nrf::updater;
+use embassy_nrf::{
+    gpio::{Input, Pull},
+    gpio::{Level, Output, OutputDrive},
+    nvmc::Nvmc,
+    Peripherals,
+};
+use embassy_traits::adapter::BlockingAsync;
+use embedded_hal::digital::v2::InputPin;
+use panic_reset as _;
+
+static APP_B: &[u8] = include_bytes!("../../b.bin");
+
+#[embassy::main]
+async fn main(_s: embassy::executor::Spawner, p: Peripherals) {
+    let mut button = Input::new(p.P0_11, Pull::Up);
+    let mut led = Output::new(p.P0_13, Level::Low, OutputDrive::Standard);
+    //let mut led = Output::new(p.P1_10, Level::Low, OutputDrive::Standard);
+    //let mut button = Input::new(p.P1_02, Pull::Up);
+
+    let nvmc = Nvmc::new(p.NVMC);
+    let mut nvmc = BlockingAsync::new(nvmc);
+
+    loop {
+        button.wait_for_any_edge().await;
+        if button.is_low().unwrap() {
+            let mut updater = updater::new();
+            let mut offset = 0;
+            for chunk in APP_B.chunks(4096) {
+                let mut buf: [u8; 4096] = [0; 4096];
+                buf[..chunk.len()].copy_from_slice(chunk);
+                updater
+                    .write_firmware(offset, &buf, &mut nvmc)
+                    .await
+                    .unwrap();
+                offset += chunk.len();
+            }
+            updater.mark_update(&mut nvmc).await.unwrap();
+            led.set_high();
+            cortex_m::peripheral::SCB::sys_reset();
+        }
+    }
+}
diff --git a/examples/boot/src/bin/b.rs b/examples/boot/src/bin/b.rs
new file mode 100644
index 000000000..18bb6330c
--- /dev/null
+++ b/examples/boot/src/bin/b.rs
@@ -0,0 +1,26 @@
+#![no_std]
+#![no_main]
+#![macro_use]
+#![feature(generic_associated_types)]
+#![feature(type_alias_impl_trait)]
+
+use embassy::time::{Duration, Timer};
+use embassy_nrf::{
+    gpio::{Level, Output, OutputDrive},
+    Peripherals,
+};
+
+use panic_reset as _;
+
+#[embassy::main]
+async fn main(_s: embassy::executor::Spawner, p: Peripherals) {
+    let mut led = Output::new(p.P0_13, Level::Low, OutputDrive::Standard);
+    //let mut led = Output::new(p.P1_10, Level::Low, OutputDrive::Standard);
+
+    loop {
+        led.set_high();
+        Timer::after(Duration::from_millis(300)).await;
+        led.set_low();
+        Timer::after(Duration::from_millis(300)).await;
+    }
+}