RPi4 custom image ################# This chapter offers a detailed guide for creating a custom image for the Raspberry Pi 4 (RPi4). Key Buildroot components and concepts will be introduced. The process outlined here can be adapted for use with other boards. For advanced features not covered in this guide, please consult the `Buildroot manual `_ This guide was done on ``Ubuntu 22.04`` Prepare the workspace ********************* The workspace is structured to utilize Buildroot without any modifications. Execute the following commands: .. code-block:: mkdir rpi4_buildroot_lvgl && cd rpi4_buildroot_lvgl mkdir resources && cd resources mkdir board mkdir configs touch Config.in && touch external.desc && touch external.mk echo "name: rpi4_lvgl" >> external.desc echo "desc: rpi4 lvgl custom build" >> external.desc cd .. Each folder utility will be explained throughout the guide. Get Buildroot ************* First, according to the `Builroot Manual `_, Buildroot requires certain packages to be installed before starting the build. Lets install them using Ubuntu's package manager. .. code-block:: bash sudo apt install sed make binutils gcc g++ bash patch gzip bzip2 perl tar \ cpio python3 unzip rsync wget libncurses-dev Now that we have satisfied all the prerequisites lets download a stable release of Buildroot. .. code-block:: bash git clone --branch 2024.08 --depth 1 https://github.com/buildroot/buildroot.git Create RPi4 image ***************** Let's see if there is already a configuration for RPi4 in Buildroot: .. code-block:: bash cd buildroot make list-defconfigs | grep rasp There is a build available for RPi4 62 bits: ``raspberrypi4_64_defconfig``. You can also find all the configurations in the Buildroot repository ``buildroot > configs`` Start with this configuration as a base, but this configuration needs to be changed to meet lvgl requirements. So let's copy this base and keep it out of Buildroot. .. code-block:: bash # move to the project root cp buildroot/configs/raspberrypi4_64_defconfig resources/configs/raspberrypi4_lvgl_defconfig Create a new file ``build.sh`` at the root of the project with this content: .. code-block:: bash #!/bin/bash SCRIPTPATH="$( cd "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )" cd $SCRIPTPATH mkdir -p output cd buildroot make defconfig O=../output BR2_DEFCONFIG=../resources/configs/raspberrypi4_lvgl_defconfig Make this file executable. .. code-block:: bash chmod +x build.sh ./build.sh Running this script creates an output folder that contains everything the process will generate: - Fetched resources - Toolchain - Images This helps maintain a clean Buildroot directory. When the script is executed, an (almost) empty folder named ``output`` is created, as the build process has not yet begun. Let's modify the configuration with ``menuconfig``. .. code-block:: bash cd output make menuconfig Change these configurations: - System host name to ``lvgl-buildroot`` under ``system_configuration > System hostname``. - Root password to ``lvgl-buildroot`` under ``system_configuration > Root password``. - Enable SSH in ``target-packages > Networking applications > openssh`` .. _build-environment: Build the image .. code-block:: bash make What happened? ************** Let's explore the contents of the output folder and what it contains. build ===== This folder contains the intermediate files and build artifacts for the various packages that are being compiled. Each package has its own subdirectory within the ``build`` folder, where the build process takes place. It includes files such as configuration files, source code, and object files that are generated as part of the build process. host ==== The ``host`` folder contains files and binaries that are built for the host system rather than the target system. This includes tools and utilities that are needed to build packages or to run the build system itself. It may contain compilers, build tools, and libraries that are required to support the build process for the target. .. _images: images ====== This directory holds the final output images generated for the target system, such as filesystem images, kernel images, or bootloader images. Depending on the configuration, you may find files like ``rootfs.tar``, ``zImage``, ``uImage``, or others that are ready to be deployed onto the target hardware. target ====== The ``target`` folder contains the files that are specifically intended for the target system. This includes the root filesystem and any additional files that will be included in the target environment. The structure within this folder often mimics the directory structure of a standard Linux system, containing directories like ``bin``, ``lib``, ``etc``, ``usr``, and others, which hold the binaries, libraries, configuration files, and other necessary components for the target system to function properly. .. _flash_the_image: Flash the image *************** Insert the SD card into the laptop and check its mount point. It is typically labeled as sda or sdb, but you can use the lsblk command to confirm this information. If it is mounted on /dev/sda, run the following command .. code-block:: bash sudo dd if=images/sdcard.img of=/dev/sda As mentioned in :ref:`images`, the output image is in ``images`` and named ``sdcard.img``. Connect an Ethernet cable to the RPi4 and ensure the laptop and the RPi4 are on the same network. You can use ``ifconfig`` or ``ip a`` to find your IP address. Then, use ``nmap`` or any tool to scan the network and find the IP address of the RPi4. .. code-block:: bash nmap -sn /24 | grep lvgl All of this can be done with the UART instead of SSH if you don't want to connect the RPi4 to the network.