Description

This repo contains:

• pico-sdk from https://github.com/raspberrypi/pico-sdk
• picotool from https://github.com/raspberrypi/picotool
• Toolchain compiler arm-none-eabi 9.3.1 from https://developer.arm.com/-/media/files/downloads/gnu-rm/9-2020q2/gcc-arm-none-eabi-9-2020-q2-update-x86_64-linux.tar.bz2
• micro_ros_raspberrypi_pico_sdk from https://github.com/micro-ROS/micro_ros_raspberrypi_pico_sdk

This repository easily sets up the environment needed to program and build for Raspberry Pi Pico (especially regarding Micro-ROS and ROS2 Jazzy) by having all stated repos together in a single directory. It includes:

• Two shell scripts:

  1. build_enviroment.sh – sets all required environment variables by injecting code into the .bashrc file and builds the required repos.
  2. build.sh – cleans and builds individual Micro-ROS projects by removing the old build folder and calling cmake with the correct arguments.

• CMakeLists.txt example and helper_functions.cmake – contain important functions and lines to help organize and understand the building process easily and cleanly. (The building process of Micro-ROS on Pico is very messy and sometimes obscure.)

• Multiple organized code folders, each acting as its own library (with src, include folders, and a CMakeLists.txt) to be modularly used in projects. These libraries vary from Micro-ROS management and wrapper classes to code that interacts with and manages sensor modules such as IMU and GPS.

• apps folder – where Micro-ROS projects can be created for clean organization. Projects do not necessarily have to be in this directory, but this is recommended.

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1. Install Dependencies

The official micro_ros_raspberrypi_pico_sdk README also lists git and doxygen as dependencies. Additionally, docker is needed to run the micro-ROS agent.

sudo apt update
sudo apt install cmake python3 build-essential gcc-arm-none-eabi libnewlib-arm-none-eabi libstdc++-arm-none-eabi-newlib pkg-config libusb-1.0-0-dev git doxygen docker.io
sudo systemctl enable docker

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2. Configure Environment Variables

Edit the .bashrc file to include environment variables describing the locations of the different directories.

• Automatic: Run build_enviroment.sh in the root directory (recommended and you wont have to do steps #3 till #5).
• Manual: Copy the block between the two EOF markers from the script and update the MICROROS_PATH variable to your repo root path.

Notes:

• Running build_enviroment.sh will overwrite any manually added code between the markers.
• Make the script executable:

  chmod +x build_enviroment.sh

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3. Build pico-sdk

pico-sdk does not need explicit building with cmake or make, since it is compiled automatically when building your executable using its source and include folders.

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4. Build picotool

picotool is used to control the Raspberry Pi Pico (load, reboot, etc.) and is important for Micro-ROS.

cd picotool
mkdir build
cd build
cmake ..
make

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5. Build micro_ros_raspberrypi_pico_sdk

The static library is precompiled in micro_ros_raspberrypi_pico_sdk/libmicroros. Building will create a demo to verify everything is working.

cd micro_ros_raspberrypi_pico_sdk
mkdir build
cd build
cmake ..
make

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6. CMakeLists.txt and helper functions

Inside the pico_w_libraries directory:

• The example CMakeLists.txt should be read carefully, it can be copied inside every project directory and edited to suit your needs.
• The first half and the absolute end of the file should barely be changed across projects.
• The middle sections can be adapted to your coding style.
• Understanding helper_functions.cmake and at least one library’s CMakeLists.txt is important.

All of this assumes familiarity with CMake.

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7. Using build.sh for Micro-ROS Projects

• Copy build.sh into the root directory of your Micro-ROS project folder.
  • Example: multiple_sensor_publisher/build.sh
• build.sh deletes the old build folder (with confirmation), runs cmake with the toolchain compiler, then calls make.

Important Notes:

• Deleting and rebuilding the build folder often resolves old compile issues that otherwise wont be resolved.
• Make build.sh executable:

  chmod +x build.sh

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Notes

• The environment only needs to be built once unless the repo folder is moved.
• After building, the generated .uf2 file is needed to flash the Pi Pico. Location depends on your CMakeLists.txt (example: build/bin).
• Flashing:

  flash_raspberrypi_pico 'path/to/your/file.uf2'

• After the first environment build, source .bashrc if building apps in the same shell:

  source ~/.bashrc

• Libraries may have dependencies on each other. Read their CMakeLists.txt carefully.
• Open and read comments in both build_enviroment.sh and build.sh, they explain very important things in great detail.