hmvp / rp2040-boot2-rs

Second stage bootloader for the RP2040, suitable for use with a Rust application.

Raspberry Pi RP2040 Second-Stage Bootloader

This is a second stage bootloader for the Raspberry Pi RP2040 SoC. Currently only the W25Q080 flash chip (as used on the Pico) is supported.

You can use this crate to include a second-stage bootloader in your application. Simply ensure that your linker script puts the array exported by this crate at the start of your flash image (0x000 to 0x100).

Instructions

Add to your main.rs:

#[link_section = ".boot_loader"]
#[used]
pub static BOOT_LOADER: [u8; 256] = rp2040_boot2::BOOT_LOADER;

Add to your application's Cargo.toml:

rp2040_boot2 = "*" # Latest from crates.io, or do
rp2040_boot2 = { git = "https://github.com/rp-rs/rp2040_boot2", branch="main" } # Latest from github

And add to your application's memory.x:

MEMORY
{
  /* NOTE 1 K = 1 KiBi = 1024 bytes */
  /* To suit Raspberry Pi RP2040 SoC */
  BOOT_LOADER : ORIGIN = 0x10000000, LENGTH = 0x100
  FLASH : ORIGIN = 0x10000100, LENGTH = 2048K - 0x100
  RAM : ORIGIN = 0x20000000, LENGTH = 256K
}

SECTIONS {

  /* ### Boot loader */
  .boot_loader ORIGIN(BOOT_LOADER) :
  {
    KEEP(*(.boot_loader*));
  } > BOOT_LOADER

} INSERT BEFORE .text;

Features

For flash to RAM memcpy in boot2, you can specify the feature flag ram_memcpy, this will move all the contents from flash to RAM (up to RAM length). Using this strategy allows for faster execution and flash availability for persistent storage.

Additionally, you need to change your linker script in order to specify the VMAs & LMAs for all the RAM sections, as in this example

    .text : {
      ...
    } > RAM AT > FLASH

Licence

The assembly source is Copyright Raspberry Pi Trading and licensed under a BSD 3-clause licence. See source files for details.

The build.rs file is licensed as CC0.