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>

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

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+[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

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+[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

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+# 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

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+//! 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

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+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

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+#![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

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+#![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;
+    }
+}