rp-hal

Rust support for the "Raspberry Silicon" family of microcontrollers
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Table of Contents

1. Getting Started
2. Programming
3. Roadmap
4. Contributing
5. License
6. Contact
7. Acknowledgements

Getting Started

So, you want to program your new Raspberry Silicon microcontroller, using the Rust programming language. You've come to the right place!

This repository is rp-hal - a collection of high-level drivers for the Raspberry Silicon RP2040 microcontroller and various associated boards, like the Raspberry Pi Pico and the Adafruit Feather RP2040.

If you want to write an application for Raspberry Silicon, check out our RP2040 Project Template.

If you want to write code that uses the Raspberry Silicon PIO State Machines, check out pio-rs. You can even compile PIO programs at run-time, on the RP2040 itself!

If you want to try out some examples on one of our supported boards, check out the list of Board Support Packages, and click through to see the various examples for each board.

Before trying any of the examples, please ensure you have the latest stable version of Rust installed, along with the right target support:

rustup self update
rustup update stable
rustup target add thumbv6m-none-eabi

You may also want to install these helpful tools:

# Useful to creating UF2 images for the RP2040 USB Bootloader
cargo install elf2uf2-rs --locked
# Useful for flashing over the SWD pins using a supported JTAG probe
cargo install probe-rs --features cli --locked

Packages

There is a Hardware Abstraction Layer (or HAL) crate for the RP2040 chip, and Board Support Package crates for a number of RP2040 based PCBs. If you are writing code that should run on any microcontroller, consider using the generic Rust Embedded Working Group's Embedded HAL.

If you are writing code that should work on any RP2040 device, use the HAL crate. If you are running code on a specific board, use the appropriate BSP crate (which will include the HAL crate for you). Please note, you cannot depend on multiple BSP crates; you have to pick one, or use Cargo Features to select one at build time.

Each BSP includes some examples to show off the features of that particular board.

rp2040-hal - The HAL for the Raspberry Silicon RP2040

You should include this crate in your project if you want to write a driver or library that runs on the Raspberry Silicon RP2040, or if you are writing a Board Support Package (see later on).

The crate provides high-level drivers for the RP2040's internal peripherals, such as the SPI Controller and the I²C Controller. It doesn't know anything about how your particular board is wired up (such as what each IO pin of the RP2040 is connected to).

There are examples in this crate to show how to use various peripherals (GPIO, I²C, SPI, UART, etc) but note that the pin-outs may not match any particular board.

BSPs - Board support packages

There are BSPs for various boards based on the RP2040 avaialble in a separate repository.

Programming

Rust generates standard Arm ELF files, which you can load onto your Raspberry Pi Silicon device with your favourite Arm flashing/debugging tool. In addition, the RP2040 contains a ROM bootloader which appears as a Mass Storage Device over USB that accepts UF2 format images. You can use the elf2uf2-rs package to convert the Arm ELF file to a UF2 format image.

For boards with USB Device support like the Raspberry Pi Pico, we recommend you use the UF2 process.

The RP2040 contains two Cortex-M0+ processors, which execute Thumb-2 encoded ARMv6-M instructions. There are no operating-specific features in the binaries produced - they are for 'bare-metal' systems. For compatibilty with other Arm code (e.g. as produced by GCC), Rust uses the Arm Embedded-Application Binary Interface standard or EABI. Therefore, any Rust code for the RP2040 should be compiled with the target thumbv6m-none-eabi.

More details can be found in the Project Template.

Linker flags

Besides the correct target, which mainly defines the instruction set, it's also necessary to use a certain memory layout compatible with the rp2040. To achieve that, rustc must be called with appropriate linker flags. In the Project Template, those flags are defined in .cargo/config.toml. Another necessary file is memory.x.

More detailed information on how the linker flags work can be found in the cortex_m_rt docs.

In most cases, it should be sufficient to use the example files from the Project Template.

Loading a UF2 over USB

Step 1 - Install elf2uf2-rs:

$ cargo install elf2uf2-rs --locked

Step 2 - Make sure your .cargo/config contains the following (it should by default if you are working in this repository):

[target.thumbv6m-none-eabi]
runner = "elf2uf2-rs -d"

The thumbv6m-none-eabi target may be replaced by the all-Arm wildcard 'cfg(all(target_arch = "arm", target_os = "none"))'.

Step 3 - Boot your RP2040 into "USB Bootloader mode", typically by rebooting whilst holding some kind of "Boot Select" button. On Linux, you will also need to 'mount' the device, like you would a USB Thumb Drive.

Step 4 - Use cargo run, which will compile the code and started the specified 'runner'. As the 'runner' is the elf2uf2-rs tool, it will build a UF2 file and copy it to your RP2040.

$ cargo run --release --example pwm_blink

Loading with probe-rs

probe-rs is a library and a command-line tool which can flash a wide variety of microcontrollers using a wide variety of debug/JTAG probes. Unlike using, say, OpenOCD, probe-rs can autodetect your debug probe, which can make it easier to use.

Step 1 - Install probe-rs:

$ cargo install probe-rs --features cli --locked

Step 2 - Make sure your .cargo/config contains the following:

[target.thumbv6m-none-eabi]
runner = "probe-rs run --chip RP2040"

Step 3 - Connect your USB JTAG/debug probe (such as a Raspberry Pi Pico running this firmware) to the SWD programming pins on your RP2040 board. Check the probe has been found by running:

$ probe-rs list
The following debug probes were found:
[0]: J-Link (J-Link) (VID: 1366, PID: 0101, Serial: 000099999999, JLink)

There is a SEGGER J-Link connected in the example above - the message you see will reflect the probe you have connected.

Step 4 - Use cargo run, which will compile the code and start the specified 'runner'. As the 'runner' is the probe-rs tool, it will connect to the RP2040 via the first probe it finds, and install your firmware into the Flash connected to the RP2040.

$ cargo run --release --example pwm_blink

Loading with picotool

As ELF files produced by compiling Rust code are completely compatible with ELF files produced by compiling C or C++ code, you can also use the Raspberry Pi tool picotool. The only thing to be aware of is that picotool expects your ELF files to have a .elf extension, and by default Rust does not give the ELF files any extension. You can fix this by simply renaming the file.

Also of note is that the special pico-sdk macros which hide information in the ELF file in a way that picotool info can read it out, are not supported in Rust. An alternative is TBC.

Roadmap

NOTE These packages are under active development. As such, it is likely to remain volatile until a 1.0.0 release.

See the open issues for a list of proposed features (and known issues).

Contributing

Contributions are what make the open source community such an amazing place to be learn, inspire, and create. Any contributions you make are greatly appreciated.

The steps are:

1. Fork the Project by clicking the 'Fork' button at the top of the page.
2. Create your Feature Branch (git checkout -b feature/AmazingFeature)
3. Make some changes to the code or documentation.
4. Commit your Changes (git commit -m 'Add some AmazingFeature')
5. Push to the Feature Branch (git push origin feature/AmazingFeature)
6. Create a New Pull Request
7. An admin will review the Pull Request and discuss any changes that may be required.
8. Once everyone is happy, the Pull Request can be merged by an admin, and your work is part of our project!

Code of Conduct

Contribution to this crate is organized under the terms of the Rust Code of Conduct, and the maintainer of this crate, the rp-rs team, promises to intervene to uphold that code of conduct.

License

The contents of this repository are dual-licensed under the MIT OR Apache 2.0 License. That means you can choose either the MIT license or the Apache-2.0 license when you re-use this code. See MIT or APACHE2.0 for more information on each specific license.

Any submissions to this project (e.g. as Pull Requests) must be made available under these terms.

Contact

Raise an issue: https://github.com/rp-rs/rp-hal/issues Chat to us on Matrix: #rp-rs:matrix.org

Acknowledgements

• Othneil Drew's README template
• Rust Embedded Working Group
• Raspberry Pi and the Pico SDK