Using Qt 5.6 and Later under LGPL

Up to Qt 5.3, things were pretty simple. Most modules were under LGPLv2.1 with the exception of some commercial modules. Starting with Qt 5.4, new Qt modules were published under LGPLv3 and old modules additionally under LGPLv3. With Qt 5.6, we now have quite a patchwork of modules under different licenses. Qt 5.7 will drop LGPLv2.1 completely. Some companies stay on Qt 5.3, because they are afraid of LGPLv3. Let me bring some clarity into this patchwork and explain how you can still use Qt under LGPL and sleep well.
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Remote Support for Harvester Terminal via VNC

The maize harvest is in full swing. The harvester runs nearly 24/7. The driver notices a drop in the area cut per hour. He calls tech support and starts sharing the screen of the terminal in the harvester. The support technician guides guides the driver through changing some machine parameters. All is fine again. My Italian business partner, Ispirata, and I developed a VNC server for the Freescale i.MX53 terminal of Krone’s BiGX forage harvester – to make this scenario possible.
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Running a QML HMI on an ARM11 without OpenGL

Recently, I brought up Qt 5.5 on a Freescale i.MX35, which has an ARM11 CPU but no OpenGL support. Despite the missing OpenGL, I wanted to write the HMI with QML. The additional challenge was that the cross-compilation toolchain was 32-bit, but I wanted to use my standard 64-bit Ubuntu. I’ll show in this post how to set up the 32-bit toolchain and rootfs on my 64-bit Ubuntu machine, how to configure and build Qt 5.5 from the sources, and how to run a hello-world application written in QML on the i.MX35. Continue reading

Solution Overview – Beacon-Enabled Museum Guides

I’ll explain how a beacon-enabled museum guide app uses an instance-based classification algorithm – a k nearest-neighbour algorithm – to locate one out of many exhibits in a room. Before diving into the details of the k nearest-neighbour algorithm, I argue why the obvious algorithm of choosing the beacon with minimum distance from the phone isn’t good enough and why we need a cleverer algorithm.
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Motivation – Beacon-Enabled Museum Guides

When you enter a museum, your phone starts the guide app of the museum automatically. When you look at an exhibit in the museum, the app starts playing the audio commentary of this exhibit. The app provides additional information like web links, videos, photos and texts. When you take photos, the app adds the photos as additional information to the exhibit you are looking at. When you finally reach home, you have your personalised museum guide and you can relive your tour through the museum whenever you want. This is the kind of experience you should expect in 2016.
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Responsive QML HMIs with File Selectors

In my previous post, I have shown how to use scaling to adapt QML HMIs to different screen sizes and formats. We reach the limits of scaling if we must change the structure of the HMI or if the HMI must be pixel-perfect. The solution to these problems is to provide a different implementation for each screen size. Switching between these different implementations is done with QML file selectors.
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