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.

examples/boot/.cargo/config.toml

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+[unstable]
+namespaced-features = true
+build-std = ["core"]
+build-std-features = ["panic_immediate_abort"]
+
+[build]
+target = "thumbv7em-none-eabi"

examples/boot/Cargo.toml

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+[package]
+authors = ["Ulf Lilleengen <lulf@redhat.com>"]
+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"

examples/boot/README.md

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+# 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
+```

examples/boot/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");
+}

examples/boot/memory.x

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+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);

examples/boot/src/bin/a.rs

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+#![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();
+        }
+    }
+}

examples/boot/src/bin/b.rs

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+#![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;
+    }
+}