This projects provides a Buildroot config and helper scripts to build an environment for Qt development on embedded systems. The primary target platform is the Raspberry Pi (A, B(+) and 2).

The following procedure will create a Buildroot environment that allows you to compile Qt applications for the platforms supported by Buildroot. It will also create a root filesystem for the target platform that contains a basic embedded Linux environment and the Qt libraries. If you want to use the root file system you will need a SD card. This repository contains an installation script for the Raspberry Pi partition layout that will copy the root file system to the SD card. It starts the Buildroot Linux system with an SSH daemon. This setup allows you to develop Qt applications with the Qt Creator on your host system and then deploy to the Raspberry. Developing Qt applications for the Raspberry has never been easier!

• Buildroot project: http://buildroot.net/
• Qt project: http://www.qt.io/

As an example project you can check out Die Brummbere, which boots the Raspberry directly into a Qt ownCould music player.

Buildroot-Qt-Dev source code is distributed under the GNU GENERAL PUBLIC LICENSE Version 3.

The repository contains a shell script that will execute all the steps that I describe below. To build the Buildroot environment in one step just type:

$ ./build.sh

This will build everything for the Raspberry 2. You can pass a parameter raspi to the script to build for Raspberry A/B(+):

$ ./build.sh raspi

There are two experimental configurations that use systemd instead of busybox as init system. Those are called raspi2-systemd and raspi-systemd. The simpler and default busybox init system should work fine for most use cases.

After the build is done you can directly jump to the section to install the root filesystem on your SD card.

After building, the Buildroot environment will provide the following Qt modules:

• GUI with Widgets and OpenGL
• Declarative with Qt Quick
• Qt Quick Controls
• DBus
• Multimedia (with GStreamer backend)
• Image Formats
• Connectivity
• Graphical Effects

Network connections via SSL/TLS are supported.

For graphical output the system supports LinuxFB and EGLFS. The latter is the default. For more information about the configuration of the platform plugins and Qt on embedded platforms please visit:

http://doc.qt.io/qt-5/embedded-linux.html

The Linux system uses busybox for most command line tools and the init system. It is a very basic system that you may adapt to your needs via the Buildroot configuration system. Besides Qt, the following libraries and applications are built and installed:

• SSL/TLS libaries
• Image format libraries (JPEG, PNG, etc.)
• Some fonts
• GStreamer with ALSA support (for the Qt multimedia module)
• OpenSSH (to be able to connect to the device and use Qt Creator later)
• NTP client (to synchronize time, as the Raspberry does not have a real-time clock)
• rpi-firmware and rpi-userland (for OpenGL support on the Raspberry)

You can see a full list of the packages that are enabled in the file config/buildroot-raspi.conf.

In addition to Buildroot's default init scripts the scripts of this repository install and start two daemons:

• An NTP client to set the current date/time
• The OpenSSH daemon

The script in scripts/postbuild.sh is responsible to copy the two init scripts to the root file system after building everything. It is automatically called by Buildroot. The two init scripts are in userland/target.

In this step we will build a complete Linux system including the kernel and the Qt libraries.

First you need to download this repository and Buildroot. We will use the the current release 2015-05 of Buildroot, which is the first release that supports the Raspberry 2. Just download and unpack Buildroot into your clone of buildroot-qt-dev:

$ git clone https://github.com/pbouda/buildroot-qt-dev.git
$ cd buildroot-qt-dev
$ wget http://buildroot.net/downloads/buildroot-2015.05.tar.bz2
$ tar xjvf buildroot-2015.05.tar.bz2

In the next step we configure buildroot for the Raspberry Pi 2 and a complete Qt framework with dependencies like GStreamer. The folder config contains a Buildroot configuration file to set all options that we need. Enter the buildroot-2015.05 folder and load the configuration:

$ cd buildroot-2015.05
$ make defconfig BR2_DEFCONFIG=../config/buildroot-raspi2.conf

If you want to build the system for Raspberry A/B(+) then choose the "-raspi" configuration file during this step:

$ cd buildroot-2015.05
$ make defconfig BR2_DEFCONFIG=../config/buildroot-raspi.conf

You can now start the build process. This will download and build the toolchain, Linux and all libraries and applications. The whole procedure might take a while, up to a few hours. Just run:

$ make

Buildroot will put all results of the build process in the folder output.

In this step we will install the root file system on a SD card that will boot the Raspberry. Buildroot put the file system into a folder output/images. We will extract the image from there. But first, we have to prepare the SD card with a specific partition layout for the Raspberry.

The SD card has to co be prepared with a certain partition layout in order to be bootable on the Raspberry. The standard layout is a small FAT partition and a larger ext4 partition in this order. The easiest way to prepare the card is to install a standard Raspbian on the card. This will also install the mandatory binary firmware and license to boot the Raspberry. You can find information about the process on the Raspberry download page:

https://www.raspberrypi.org/downloads/

Just follow the instructions given on the page under the Raspbian heading.

To install the root file system we will now format the second partition on the SD card with an ext4 file system, extract the file system that Buildroot created and copy the Buildroot kernel onto the first FAT partition. The repository contains the file script/installrootfs.sh that executes all commands. The script needs to know the device of your SD card. Please check carefully which device your SD card uses and adapt the script. Currently the device for the SD card is /dev/sdX. Change those device names to your setup in all locations.

If your SD card is still mounted from the previous step you might just call mount to see a list of all file systems. Find your SD card in this list and use the device names that are listed (like /dev/sdc1 and /dev/sdc2).

Careful: Your SD card has to prepared with the two Raspberry partitions. If you do not edit the script installrootfs.sh with the correct device names your hard disk might get formatted!

You can now run the script. The script expects the path to the root file system image and the kernel as the first argument. Buildroot puts those in the folder output/images. So change directory into scripts and run installrootfs.sh with the absolute path to your buildroot-2015.05/output/images folder:

$ cd ../scripts/
$ ./installrootfs.sh /path/to/buildroot-qt-dev/buildroot-2015.05/output/images

This will format, extract and copy. After the script finishes it is safe to remove the SD card from your computer and insert it into your Raspberry. Power on the Raspberry and see the system boot. If you attached a network cable you should be able open a shell via SSH. The username is root with password raspi. Here is a nice one liner to find your Raspberry on the network (needs nmap installed):

$ sudo nmap -sP 192.168.1.0/24 | awk '/^Nmap/{ip=$NF}/B8:27:EB/{print ip}'

[via pierre-o's Known]

You can now use the Buildroot qmake executable to generate your Qt project. The command is available in Buildroot's output/host/usr/bin directory.

As an example, we will compile the project Die Brummbeere. Just check out the code, run qmake followed by make:

$ cd ..
$ git clone https://github.com/pbouda/brummbeere.git
$ cd brummbeere/src/
$ ../../buildroot-2015.05/output/host/usr/bin/qmake Brummbeere.pro
$ make

This will build the executable brummbeere in the mainapp directory. You can now copy the executable to the Raspbery and run Die Brummbeere.

See doc/qtcreator.md.

Contact me here: http://www.peterbouda.eu/#contact

I am available to hire, contact me if you need a programmer for your Embedded Qt project!