We have succeeded in building embedded Linux with Yocto for a quad-core NXP i.MX6 (ARM Cortex-A9). Next, we want to cross-compile our own Qt application. As we use CMake for building our Qt application, we must create a CMake toolchain file. I am going to give a line-line by line explanation of the CMake toolchain file. I used Yocto Morty and CMake v3.5.1 (as it comes with Ubuntu 16.04 LTS).
Read More »CMake Cross-Compilation Based on Yocto SDK
Update: Since Qt 5.12, the QtQuick compiler has been available under LGPLv3. Even if you don’t have a commercial Qt license, you will be able to enjoy a significantly faster startup of embedded QML applications.
It is not easy to find hard data about how much the QtQuick compiler can speed up the startup of real-life application. As I had some time on my hands this weekend, I measured the startup times of the HMI of a maize harvester running on a quad-core NXP/Freescale i.MX6 (Nit6Q_W_BCOM). Using the QtQuick compiler from Qt 5.7 brings the startup time from 2.72s down to 1.91s – a speedup of 30%!
Read More »30% Faster Startup Thanks to QtQuick Compiler
The answer to the question in the title is a resounding “maybe”. The writer of a piece of code wanted to avoid a division-by-zero error by checking whether the divisor of type float is not equal to 0.0f.
Read More »Is a C++ Float Variable Ever Equal to 0.0f?
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.Read More »Running a QML HMI on an ARM11 without OpenGL
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.
Read More »Responsive QML HMIs with File Selectors
The HMIs of in-vehicle infotainment systems, TVs, phones and many other systems must adapt to different screen resolutions and formats. This adaptation should happen with as little duplicate effort as possible. The simplest way of doing this for QML HMIs is to scale the values of all x, y, width, height, margin and border properties in proportion to a reference resolution. Based on the HMI of a music player, I’ll show you how to do this by changing only the screen width and height. Read More »Responsive QML HMIs with Scaling