feat: embassy-boot for rp2040

Add embassy-boot support for RP2040, with examples for the Raspberry Pi
Pico.

Co-authored-by: Mathias Koch <mk@blackbird.online>

ci.sh

@@ -81,6 +81,7 @@ cargo batch  \
     --- build --release --manifest-path embassy-stm32/Cargo.toml --target thumbv7m-none-eabi --features nightly,stm32f103re,defmt,exti,time-driver-any,unstable-traits \
     --- build --release --manifest-path embassy-stm32/Cargo.toml --target thumbv7m-none-eabi --features nightly,stm32f100c4,defmt,exti,time-driver-any,unstable-traits \
     --- build --release --manifest-path embassy-boot/nrf/Cargo.toml --target thumbv7em-none-eabi --features embassy-nrf/nrf52840 \
+    --- build --release --manifest-path embassy-boot/rp/Cargo.toml --target thumbv6m-none-eabi \
     --- build --release --manifest-path embassy-boot/stm32/Cargo.toml --target thumbv7em-none-eabi --features embassy-stm32/stm32wl55jc-cm4 \
     --- build --release --manifest-path docs/modules/ROOT/examples/basic/Cargo.toml --target thumbv7em-none-eabi \
     --- build --release --manifest-path docs/modules/ROOT/examples/layer-by-layer/blinky-pac/Cargo.toml --target thumbv7em-none-eabi \
@@ -106,6 +107,7 @@ cargo batch  \
     --- build --release --manifest-path examples/stm32wb/Cargo.toml --target thumbv7em-none-eabihf --out-dir out/examples/stm32wb \
     --- build --release --manifest-path examples/stm32wl/Cargo.toml --target thumbv7em-none-eabihf --out-dir out/examples/stm32wl \
     --- build --release --manifest-path examples/boot/application/nrf/Cargo.toml --target thumbv7em-none-eabi --out-dir out/examples/boot/nrf --bin b \
+    --- build --release --manifest-path examples/boot/application/rp/Cargo.toml --target thumbv6m-none-eabi --out-dir out/examples/boot/rp --bin b \
     --- build --release --manifest-path examples/boot/application/stm32f3/Cargo.toml --target thumbv7em-none-eabi --out-dir out/examples/boot/stm32f3 --bin b \
     --- build --release --manifest-path examples/boot/application/stm32f7/Cargo.toml --target thumbv7em-none-eabi --out-dir out/examples/boot/stm32f7 --bin b \
     --- build --release --manifest-path examples/boot/application/stm32h7/Cargo.toml --target thumbv7em-none-eabi --out-dir out/examples/boot/stm32h7 --bin b \
@@ -114,6 +116,7 @@ cargo batch  \
     --- build --release --manifest-path examples/boot/application/stm32l4/Cargo.toml --target thumbv7em-none-eabi --out-dir out/examples/boot/stm32l4 --bin b \
     --- build --release --manifest-path examples/boot/application/stm32wl/Cargo.toml --target thumbv7em-none-eabihf --out-dir out/examples/boot/stm32wl --bin b \
     --- build --release --manifest-path examples/boot/bootloader/nrf/Cargo.toml --target thumbv7em-none-eabi --features embassy-nrf/nrf52840 \
+    --- build --release --manifest-path examples/boot/bootloader/rp/Cargo.toml --target thumbv6m-none-eabi \
     --- build --release --manifest-path examples/boot/bootloader/stm32/Cargo.toml --target thumbv7em-none-eabi --features embassy-stm32/stm32wl55jc-cm4 \
     --- build --release --manifest-path examples/wasm/Cargo.toml --target wasm32-unknown-unknown --out-dir out/examples/wasm \
     --- build --release --manifest-path tests/stm32/Cargo.toml --target thumbv7m-none-eabi --features stm32f103c8 --out-dir out/tests/bluepill-stm32f103c8 \

docs/modules/ROOT/pages/bootloader.adoc

@@ -15,6 +15,7 @@ The bootloader supports
 
 * nRF52 with and without softdevice
 * STM32 L4, WB, WL, L1, L0, F3, F7 and H7
+* Raspberry Pi: RP2040
 
 In general, the bootloader works on any platform that implements the `embedded-storage` traits for its internal flash, but may require custom initialization code to work.
 

embassy-boot/rp/Cargo.toml

@@ -0,0 +1,71 @@
+[package]
+edition = "2021"
+name = "embassy-boot-rp"
+version = "0.1.0"
+description = "Bootloader lib for RP2040 chips"
+license = "MIT OR Apache-2.0"
+
+[package.metadata.embassy_docs]
+src_base = "https://github.com/embassy-rs/embassy/blob/embassy-boot-rp-v$VERSION/src/"
+src_base_git = "https://github.com/embassy-rs/embassy/blob/$COMMIT/embassy-boot/rp/src/"
+target = "thumbv6m-none-eabi"
+
+[lib]
+
+[dependencies]
+defmt = { version = "0.3", optional = true }
+defmt-rtt = { version = "0.4", optional = true }
+log = { version = "0.4", optional = true }
+
+embassy-sync = { path = "../../embassy-sync" }
+embassy-rp = { path = "../../embassy-rp", default-features = false, features = ["nightly"] }
+embassy-boot = { path = "../boot", default-features = false }
+cortex-m = { version = "0.7.6" }
+cortex-m-rt = { version = "0.7" }
+embedded-storage = "0.3.0"
+embedded-storage-async = "0.3.0"
+cfg-if = "1.0.0"
+
+[features]
+defmt = [
+    "dep:defmt",
+    "embassy-boot/defmt",
+    "embassy-rp/defmt",
+]
+log = [
+    "dep:log",
+    "embassy-boot/log",
+    "embassy-rp/log",
+]
+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

embassy-boot/rp/README.md

@@ -0,0 +1,26 @@
+# embassy-boot-rp
+
+An [Embassy](https://embassy.dev) project.
+
+An adaptation of `embassy-boot` for RP2040.
+
+NOTE: The applications using this bootloader should not link with the `link-rp.x` linker script.
+
+## Features
+
+* Configure bootloader partitions based on linker script.
+* Load applications from active partition.
+
+## Minimum supported Rust version (MSRV)
+
+`embassy-boot-rp` requires Rust nightly to compile as it relies on async traits for interacting with the flash peripherals.
+
+## License
+
+This work is licensed under either of
+
+- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
+  <http://www.apache.org/licenses/LICENSE-2.0>)
+- MIT license ([LICENSE-MIT](LICENSE-MIT) or <http://opensource.org/licenses/MIT>)
+
+at your option.

embassy-boot/rp/build.rs

@@ -0,0 +1,8 @@
+use std::env;
+
+fn main() {
+    let target = env::var("TARGET").unwrap();
+    if target.starts_with("thumbv6m-") {
+        println!("cargo:rustc-cfg=armv6m");
+    }
+}

embassy-boot/rp/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
+    }
+}

embassy-boot/rp/src/lib.rs

@@ -0,0 +1,90 @@
+#![no_std]
+#![feature(type_alias_impl_trait)]
+#![warn(missing_docs)]
+#![doc = include_str!("../README.md")]
+mod fmt;
+
+pub use embassy_boot::{AlignedBuffer, BootFlash, FirmwareUpdater, FlashConfig, Partition, SingleFlashConfig, State};
+use embassy_rp::flash::{ERASE_SIZE, WRITE_SIZE};
+
+/// A bootloader for RP2040 devices.
+pub struct BootLoader {
+    boot: embassy_boot::BootLoader,
+    magic: AlignedBuffer<WRITE_SIZE>,
+    page: AlignedBuffer<ERASE_SIZE>,
+}
+
+impl BootLoader {
+    /// 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),
+            magic: AlignedBuffer([0; WRITE_SIZE]),
+            page: AlignedBuffer([0; ERASE_SIZE]),
+        }
+    }
+
+    /// Inspect the bootloader state and perform actions required before booting, such as swapping
+    /// firmware.
+    pub fn prepare<F: FlashConfig>(&mut self, flash: &mut F) -> usize {
+        match self.boot.prepare_boot(flash, self.magic.as_mut(), self.page.as_mut()) {
+            Ok(_) => embassy_rp::flash::FLASH_BASE + self.boot.boot_address(),
+            Err(_) => panic!("boot prepare error!"),
+        }
+    }
+
+    /// Boots the application.
+    ///
+    /// # Safety
+    ///
+    /// This modifies the stack pointer and reset vector and will run code placed in the active partition.
+    pub unsafe fn load(&mut self, start: usize) -> ! {
+        trace!("Loading app at 0x{:x}", start);
+        #[allow(unused_mut)]
+        let mut p = cortex_m::Peripherals::steal();
+        #[cfg(not(armv6m))]
+        p.SCB.invalidate_icache();
+        p.SCB.vtor.write(start as u32);
+
+        cortex_m::asm::bootload(start as *const u32)
+    }
+}
+
+impl Default for BootLoader {
+    /// Create a new bootloader instance using parameters from linker script
+    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)
+    }
+}

embassy-rp/src/flash.rs

@@ -59,6 +59,11 @@ impl<'d, T: Instance, const FLASH_SIZE: usize> Flash<'d, T, FLASH_SIZE> {
     }
 
     pub fn read(&mut self, offset: u32, bytes: &mut [u8]) -> Result<(), Error> {
+        trace!(
+            "Reading from 0x{:x} to 0x{:x}",
+            FLASH_BASE + offset as usize,
+            FLASH_BASE + offset as usize + bytes.len()
+        );
         check_read(self, offset, bytes.len())?;
 
         let flash_data = unsafe { core::slice::from_raw_parts((FLASH_BASE as u32 + offset) as *const u8, bytes.len()) };

examples/boot/application/rp/.cargo/config.toml

@@ -0,0 +1,12 @@
+[unstable]
+build-std = ["core"]
+build-std-features = ["panic_immediate_abort"]
+
+[target.'cfg(all(target_arch = "arm", target_os = "none"))']
+runner = "probe-run --chip RP2040"
+
+[build]
+target = "thumbv6m-none-eabi"
+
+[env]
+DEFMT_LOG = "trace"

examples/boot/application/rp/Cargo.toml

@@ -0,0 +1,33 @@
+[package]
+edition = "2021"
+name = "embassy-boot-rp-examples"
+version = "0.1.0"
+license = "MIT OR Apache-2.0"
+
+[dependencies]
+embassy-sync = { version = "0.1.0", path = "../../../../embassy-sync" }
+embassy-executor = { version = "0.1.0", path = "../../../../embassy-executor", features = ["nightly", "integrated-timers"] }
+embassy-time = { version = "0.1.0", path = "../../../../embassy-time", features = ["nightly"] }
+embassy-rp = { version = "0.1.0", path = "../../../../embassy-rp", features = ["time-driver", "unstable-traits", "nightly"] }
+embassy-boot-rp = { version = "0.1.0", path = "../../../../embassy-boot/rp" }
+embassy-embedded-hal = { version = "0.1.0", path = "../../../../embassy-embedded-hal" }
+
+defmt = "0.3"
+defmt-rtt = "0.4"
+panic-probe = { version = "0.3", features = ["print-defmt"], optional = true }
+panic-reset = { version = "0.1.1", optional = true }
+embedded-hal = { version = "0.2.6" }
+
+cortex-m = { version = "0.7.6", features = ["critical-section-single-core"] }
+cortex-m-rt = "0.7.0"
+
+[features]
+default = ["panic-reset"]
+debug = [
+    "embassy-rp/defmt",
+    "embassy-boot-rp/defmt",
+    "panic-probe"
+]
+
+[profile.release]
+debug = true

examples/boot/application/rp/README.md

@@ -0,0 +1,28 @@
+# Examples using bootloader
+
+Example for Raspberry Pi Pico demonstrating the bootloader. The example consists of application binaries, 'a'
+which waits for 5 seconds before flashing the 'b' binary, which blinks the LED.
+
+NOTE: The 'b' binary does not mark the new binary as active, so if you reset the device, it will roll back to the 'a' binary before automatically updating it again.
+
+## Prerequisites
+
+* `cargo-binutils`
+* `cargo-flash`
+* `embassy-boot-rp`
+
+## Usage
+
+```
+# Flash bootloader
+cargo flash --manifest-path ../../bootloader/rp/Cargo.toml --release --chip RP2040
+
+# Build 'b'
+cargo build --release --bin b
+
+# Generate binary for 'b'
+cargo objcopy --release --bin b -- -O binary b.bin
+
+# Flash `a` (which includes b.bin)
+cargo flash --release --bin a --chip RP2040
+```

examples/boot/application/rp/build.rs

@@ -0,0 +1,35 @@
+//! 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");
+    println!("cargo:rustc-link-arg-bins=-Tdefmt.x");
+}

examples/boot/application/rp/memory.x

@@ -0,0 +1,15 @@
+MEMORY
+{
+  /* NOTE 1 K = 1 KiBi = 1024 bytes */
+  BOOT2                             : ORIGIN = 0x10000000, LENGTH = 0x100
+  BOOTLOADER_STATE                  : ORIGIN = 0x10006000, LENGTH = 4K
+  FLASH                             : ORIGIN = 0x10007000, LENGTH = 512K
+  DFU                               : ORIGIN = 0x10087000, LENGTH = 516K
+  RAM                               : ORIGIN = 0x20000000, LENGTH = 256K
+}
+
+__bootloader_state_start = ORIGIN(BOOTLOADER_STATE) - ORIGIN(BOOT2);
+__bootloader_state_end = ORIGIN(BOOTLOADER_STATE) + LENGTH(BOOTLOADER_STATE) - ORIGIN(BOOT2);
+
+__bootloader_dfu_start = ORIGIN(DFU) - ORIGIN(BOOT2);
+__bootloader_dfu_end = ORIGIN(DFU) + LENGTH(DFU) - ORIGIN(BOOT2);

examples/boot/application/rp/src/bin/a.rs

@@ -0,0 +1,52 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt_rtt as _;
+use embassy_boot_rp::*;
+use embassy_executor::Spawner;
+use embassy_rp::flash::Flash;
+use embassy_rp::gpio::{Level, Output};
+use embassy_time::{Duration, Timer};
+#[cfg(feature = "panic-probe")]
+use panic_probe as _;
+#[cfg(feature = "panic-reset")]
+use panic_reset as _;
+
+static APP_B: &[u8] = include_bytes!("../../b.bin");
+const FLASH_SIZE: usize = 2 * 1024 * 1024;
+
+#[embassy_executor::main]
+async fn main(_s: Spawner) {
+    let p = embassy_rp::init(Default::default());
+    let mut led = Output::new(p.PIN_25, Level::Low);
+
+    let mut flash: Flash<_, FLASH_SIZE> = Flash::new(p.FLASH);
+
+    let mut updater = FirmwareUpdater::default();
+
+    Timer::after(Duration::from_secs(5)).await;
+    led.set_high();
+    let mut offset = 0;
+    let mut buf: AlignedBuffer<4096> = AlignedBuffer([0; 4096]);
+    defmt::info!("preparing update");
+    let mut writer = updater
+        .prepare_update_blocking(&mut flash)
+        .map_err(|e| defmt::warn!("E: {:?}", defmt::Debug2Format(&e)))
+        .unwrap();
+    defmt::info!("writer created, starting write");
+    for chunk in APP_B.chunks(4096) {
+        buf.0[..chunk.len()].copy_from_slice(chunk);
+        defmt::info!("writing block at offset {}", offset);
+        writer
+            .write_block_blocking(offset, &buf.0[..], &mut flash, 256)
+            .unwrap();
+        offset += chunk.len();
+    }
+    defmt::info!("firmware written, marking update");
+    updater.mark_updated_blocking(&mut flash, &mut buf.0[..1]).unwrap();
+    Timer::after(Duration::from_secs(2)).await;
+    led.set_low();
+    defmt::info!("update marked, resetting");
+    cortex_m::peripheral::SCB::sys_reset();
+}

examples/boot/application/rp/src/bin/b.rs

@@ -0,0 +1,23 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use embassy_executor::Spawner;
+use embassy_rp::gpio;
+use embassy_time::{Duration, Timer};
+use gpio::{Level, Output};
+use {defmt_rtt as _, panic_reset as _};
+
+#[embassy_executor::main]
+async fn main(_s: Spawner) {
+    let p = embassy_rp::init(Default::default());
+    let mut led = Output::new(p.PIN_25, Level::Low);
+
+    loop {
+        led.set_high();
+        Timer::after(Duration::from_millis(100)).await;
+
+        led.set_low();
+        Timer::after(Duration::from_millis(100)).await;
+    }
+}

examples/boot/bootloader/rp/.cargo/config.toml

@@ -0,0 +1,8 @@
+[target.'cfg(all(target_arch = "arm", target_os = "none"))']
+runner = "probe-run --chip RP2040"
+
+[build]
+target = "thumbv6m-none-eabi"
+
+[env]
+DEFMT_LOG = "trace"

examples/boot/bootloader/rp/Cargo.toml

@@ -0,0 +1,29 @@
+[package]
+edition = "2021"
+name = "rp-bootloader-example"
+version = "0.1.0"
+description = "Example bootloader for RP2040 chips"
+license = "MIT OR Apache-2.0"
+
+[dependencies]
+defmt = { version = "0.3", optional = true }
+defmt-rtt = { version = "0.4", optional = true }
+
+embassy-rp = { path = "../../../../embassy-rp", default-features = false, features = ["nightly"] }
+embassy-boot-rp = { path = "../../../../embassy-boot/rp", default-features = false }
+cortex-m = { version = "0.7.6", features = ["critical-section-single-core"] }
+cortex-m-rt = { version = "0.7" }
+embedded-storage = "0.3.0"
+embedded-storage-async = "0.3.0"
+cfg-if = "1.0.0"
+
+[features]
+defmt = [
+    "dep:defmt",
+    "embassy-boot-rp/defmt",
+    "embassy-rp/defmt",
+]
+debug = ["defmt-rtt", "defmt"]
+
+[profile.release]
+debug = true

examples/boot/bootloader/rp/README.md

@@ -0,0 +1,17 @@
+# Bootloader for RP2040
+
+The bootloader uses `embassy-boot` to interact with the flash.
+
+# Usage
+
+Flashing the bootloader
+
+```
+cargo flash --release --chip RP2040
+```
+
+To debug, use `cargo run` and enable the debug feature flag
+
+``` rust
+cargo run --release --features debug
+```

examples/boot/bootloader/rp/build.rs

@@ -0,0 +1,28 @@
+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");
+    println!("cargo:rustc-link-arg-bins=-Tlink-rp.x");
+    if env::var("CARGO_FEATURE_DEFMT").is_ok() {
+        println!("cargo:rustc-link-arg-bins=-Tdefmt.x");
+    }
+}

examples/boot/bootloader/rp/memory.x

@@ -0,0 +1,19 @@
+MEMORY
+{
+  /* NOTE 1 K = 1 KiBi = 1024 bytes */
+  BOOT2                             : ORIGIN = 0x10000000, LENGTH = 0x100
+  FLASH                             : ORIGIN = 0x10000100, LENGTH = 24K
+  BOOTLOADER_STATE                  : ORIGIN = 0x10006000, LENGTH = 4K
+  ACTIVE                            : ORIGIN = 0x10007000, LENGTH = 512K
+  DFU                               : ORIGIN = 0x10087000, LENGTH = 516K
+  RAM                               : ORIGIN = 0x20000000, LENGTH = 256K
+}
+
+__bootloader_state_start = ORIGIN(BOOTLOADER_STATE) - ORIGIN(BOOT2);
+__bootloader_state_end = ORIGIN(BOOTLOADER_STATE) + LENGTH(BOOTLOADER_STATE) - ORIGIN(BOOT2);
+
+__bootloader_active_start = ORIGIN(ACTIVE) - ORIGIN(BOOT2);
+__bootloader_active_end = ORIGIN(ACTIVE) + LENGTH(ACTIVE) - ORIGIN(BOOT2);
+
+__bootloader_dfu_start = ORIGIN(DFU) - ORIGIN(BOOT2);
+__bootloader_dfu_end = ORIGIN(DFU) + LENGTH(DFU) - ORIGIN(BOOT2);

examples/boot/bootloader/rp/src/main.rs

@@ -0,0 +1,51 @@
+#![no_std]
+#![no_main]
+
+use cortex_m_rt::{entry, exception};
+#[cfg(feature = "defmt")]
+use defmt_rtt as _;
+use embassy_boot_rp::*;
+use embassy_rp::flash::{Flash, ERASE_SIZE};
+use embassy_rp::peripherals::FLASH;
+
+const FLASH_SIZE: usize = 2 * 1024 * 1024;
+
+#[entry]
+fn main() -> ! {
+    let p = embassy_rp::init(Default::default());
+
+    // Uncomment this if you are debugging the bootloader with debugger/RTT attached,
+    // as it prevents a hard fault when accessing flash 'too early' after boot.
+    /*
+    for i in 0..10000000 {
+        cortex_m::asm::nop();
+    }
+    */
+
+    let mut bl: BootLoader = BootLoader::default();
+    let flash: Flash<'_, FLASH, FLASH_SIZE> = Flash::new(p.FLASH);
+    let mut flash = BootFlash::<_, ERASE_SIZE>::new(flash);
+    let start = bl.prepare(&mut SingleFlashConfig::new(&mut flash));
+    core::mem::drop(flash);
+
+    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) -> ! {
+    cortex_m::asm::udf();
+}