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embedded Linux

Docker Builds from QtCreator

On your development PC, you simply hit Ctrl+R (Run) in QtCreator to build and run your Qt application. When you want to run the application on an embedded system, you must perform four tasks:

  • You cross-build the Qt application for the target embedded system in a Docker container.
  • You stop the application on the target system.
  • You copy the application from the development PC to the target system with scp.
  • You start the application on the target system.

Wouldn’t you love to hit Ctrl+R in QtCreator and to have QtCreator perform the above four steps for you? Of course, you would! I’ll show you how in this post. Running an application on an embedded system will be the same as running the application on a PC.

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Less Love for FOSS Qt Users

From Qt 5.15, The Qt Company make their offering a bit more inconvenient for FOSS users. They announced three changes:

  • A Qt account is mandatory to download binary Qt packages. The offline installer is not available to FOSS users any more.
  • LTS (long-term support) releases are not available to FOSS users, once the next minor or major release is out.
  • Small business pay 499 USD per year, if their yearly revenue is less than 100,000 USD and they have less than five employees.

What do these changes mean for the development of Qt embedded Linux systems under LGPLv3?

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Detecting Overdraw in QML HMIs with GammaRay

Overdraw happens when one QML item fully eclipses another QML item. The QML renderer always draws both items, although there is no need to draw the eclipsed item. You must help out the renderer by explicitly setting visible: false on the eclipsed item.

On embedded systems, heavy overdraw makes animations or flicking jerky. In the worst case, it freezes your HMI. Fortunately, the Qt experts at KDAB developed a tool, GammaRay, which makes detecting overdraw a piece of cake. I’ll show you how to build GammaRay, how to detect overdraw in the home screen of a harvester HMI, and how to fix the overdraw.

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Deploying Qt Projects to Embedded Devices with CMake

When you run a Qt project, QtCreator first deploys the project to a remote embedded Linux device via ssh and then runs the executable on the remote device. This feature enables nearly instant feedback how your Qt application works on the embedded device.

Deployment works fine with the INSTALLS variable of qmake. It does not work out of the box with the install functions of CMake. Fortunately, the Qt trolls provide a workaround. I’ll explain the workaround with an example CMakeLists.txt file.

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Yocto Builds with CROPS Containers

In a recent post Using Docker Containers for Yocto Builds, I suffered an episode of NIHS (not-invented-here syndrome). I wrote a Dockerfile for Yocto builds. Stefan Agner pointed out in his comment that the CROPS project provides ready-made containers for Linux distributions like Ubuntu, Fedora and others. The crops/poky-container enables us to start our first Yocto build within minutes.

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