B2QT Build Release

From Variscite Wiki
DART-MX8M-MINI - Boot to Qt 5.12 based on Yocto Sumo

1 About Boot to Qt

Boot to Qt is a light-weight, Qt-optimized, full software stack for embedded Linux systems that is installed into the actual target device.

The stack can be customized to production with Build-Your-Own-Stack tooling, including proprietary Yocto Project recipes.


The full B2Qt documentation is available at Qt for Device Creation official page.

2 Requirements

You should be familiar with the Yocto tools and the concept of recipes. For more information, see Yocto Project documentation.

To get started, you need the following:

  • Install the dependencies for the Yocto tools. In Ubuntu, the following packages are required:
$ sudo apt-get install gawk curl git-core diffstat unzip p7zip gcc-multilib \
g++-multilib build-essential chrpath libsdl1.2-dev xterm gperf bison texinfo
$ which git-lfs > /dev/null || sudo apt-get install git-lfs || \
  (curl -s https://packagecloud.io/install/repositories/github/git-lfs/script.deb.sh | sudo bash &&
  sudo apt-get install git-lfs)

3 Setting Up Yocto Build Environment

Run the setup script that initializes the Yocto environment.

$ mkdir ~/var-b2qt
$ cd ~/var-b2qt
$ git clone https://github.com/varigit/meta-variscite-boot2qt.git -b sumo-var01
$ cd meta-variscite-boot2qt
$ ./b2qt-init-build-env init --device imx8mm-var-dart

b2qt-init-build-env has the following additional command line options:

  • list-devices: show all supported devices that can be used for a Boot to Qt build
  • mirror: create a local mirror of the yocto repositories. This enables you to use the same repository downloads for multiple build environments, when initializing with init --reference <mirror path>.

For all command line options, see:

$ ./b2qt-init-build-env help

4 Building the Image and Toolchain

After the Yocto environment is set up, you need to configure the build environment for your target device:

$ MACHINE=imx8mm-var-dart source ./setup-environment.sh

Yocto recipes for Boot to Qt for embedded Linux have two main targets to build: The target image, and the external toolchain that can be used with Qt Creator for building Qt applications.

$ MACHINE=imx8mm-var-dart bitbake b2qt-embedded-qt5-image
$ MACHINE=imx8mm-var-dart bitbake meta-toolchain-b2qt-embedded-qt5-sdk

The target rootfs image is located at:


and the new toolchain installation file is:


5 Flashing the SD card image

Plug the SD card into your Linux HOST PC, run "dmesg|tail" and see which device is added (i.e. /dev/sdX or /dev/mmcblkX)

$ sudo umount /dev/sdX*

$ sudo dd if=tmp/deploy/images/imx8mm-var-dart/b2qt-embedded-qt5-image-imx8mm-var-dart.wic of=/dev/sdX bs=1M && sync

Replace /dev/sdX with your actual device name, e.g. /dev/sdb

6 Creating an extended SD card

Variscite provides the var-create-yocto-sdcard.sh script which creates our NAND/eMMC recovery SD card. The script copies the NAND/eMMC flash burning scripts and relevant binaries for your convenience.
Later, you will be able to follow Yocto Recovery SD card guide to burn your images to NAND flash or eMMC.

Plug the SD card into your Linux HOST PC, run "dmesg|tail" and see which device is added (i.e. /dev/sdX or /dev/mmcblkX)

$ cd ~/var-b2qt/meta-variscite-boot2qt
$ sudo MACHINE=imx8mm-var-dart sources/meta-variscite-fslc/scripts/var_mk_yocto_sdcard/var-create-yocto-sdcard.sh /dev/sdX

Replace /dev/sdX with your actual device name, e.g. /dev/sdb

6.1 Create an extended SD card image using a loop device

It is also possible to use the var-create-yocto-sdcard.sh script to create an extended SD card image, while using a loop device instead of attaching a real SD card.

$ cd ~/var-b2qt/meta-variscite-boot2qt

Create an empty file using the following command:

$ dd if=/dev/zero of=imx8mm-var-dart-extended-sd.img bs=1M count=3700

The above command creates a 3700MiB file representing the SD card.

Attach the first available loop device to this file:

$ sudo losetup -Pf imx8mm-var-dart-extended-sd.img

To find the actual loop device being used, run:

$ losetup -a | grep imx8mm-var-dart-extended-sd.img

Write the content to the loop device to generate the SD card image:

$ sudo MACHINE=imx8mm-var-dart sources/meta-variscite-fslc/scripts/var_mk_yocto_sdcard/var-create-yocto-sdcard.sh <options> /dev/loopX

(Replace /dev/loopX with your actual loop device, e.g. /dev/loop0)

Detach the loop device from the file:

$ sudo losetup -d /dev/loopX

To compress the SD card image file use the following command:

$ gzip -9 imx8mm-var-dart-extended-sd.img

To write the SD card image to a real SD card device use the following command:

$ zcat imx8mm-var-dart-extended-sd.img.gz | sudo dd of=/dev/sdX bs=1M && sync

(Replace /dev/sdX with your actual SD device, e.g. /dev/sdb)