{"id":774,"date":"2015-09-20T21:35:58","date_gmt":"2015-09-21T04:35:58","guid":{"rendered":"http:\/\/visualgdb.com\/w\/?p=774"},"modified":"2015-11-13T11:48:07","modified_gmt":"2015-11-13T19:48:07","slug":"cross-compiling-qt-embedded-5-5-for-raspberry-pi-2","status":"publish","type":"post","link":"https:\/\/visualgdb.com\/tutorials\/raspberry\/qt\/embedded\/","title":{"rendered":"Cross-compiling Qt Embedded 5.5 for Raspberry Pi 2"},"content":{"rendered":"

This tutorial shows how to cross-compile the Embedded build of Qt 5.5 for Raspberry Pi 2. The Embedded build does not use the X11 server and instead displays the GUI directly using the Raspberry Pi framebuffer. We will show how to use a Raspberry Pi cross-compiler to build the Qt5 framework for Raspberry Pi on a Windows machine.<\/p>\n

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  1. Download a fresh SD card image for your Raspberry Pi. In this tutorial we will use a Debian Jessie<\/a> image. Write the image into the SD card using WinFLASHTool<\/a> or any other similar tool.<\/li>\n
  2. Download a cross-toolchain<\/a> matching the image and install it:\"01-raspberry\"<\/a><\/li>\n
  3. Download and install a MinGW toolchain<\/a> that will be used to build Windows versions of build tools like Qmake:\"02-mingw\"<\/a><\/li>\n
  4. Download and install Python 2.7 for Windows<\/a> and ensure that its directory is added to PATH.<\/li>\n
  5. Download the Qt source package (e.g. qt-everywhere-opensource-src-5.5.0.tar.xz<\/a>) from the Qt Archive<\/a>.<\/li>\n
  6. Before we can build the Qt for Raspberry Pi, we need to resynchronize the sysroot with the toolchain to ensure that the toolchain has all the headers and libraries from your Raspberry. Start the UpdateSysroot.bat<\/strong> file from the <sysgcc>\\Raspberry\\TOOLS folder:\"03-sync\"<\/a>You need to synchronize at least the \/opt folder, as it contains OpenGL headers that are not included in the toolchain. If you have installed additional packages on your Raspberry Pi, resynchronize other suggested directories as well. Do not resynchronize the \/etc folder. Otherwise it will overwrite the \/etc\/ld.so.conf file with a version from the device that contains “include” statements unsupported by the Windows compiler. If you did overwrite it, expand the statements manually or revert to the ld.so.conf file shipped with the original toolchain.<\/strong><\/li>\n
  7. Launch the msys shell from the MinGW toolchain by running <sysgcc>\\MinGW32\\msys\\1.0\\msys.bat<\/strong>:\"04-shell\"<\/a><\/li>\n
  8. Go to the directory containing the archive with the Qt source and extract it by running tar xf <archive name>:\"05-unpack\"<\/a><\/li>\n
  9. Ensure that the directories containing the MinGW gcc compiler and the Raspberry Pi cross-compiler are added to PATH. If not, add them manually:\"05a-which\"<\/a><\/li>\n
  10. Open the\u00a0qt-everywhere-opensource-src-5.5.0\\qtbase\\mkspecs\\linux-arm-gnueabi-g++\\qmake.conf\u00a0<\/strong> file and replace all occurences of arm-linux-gnueabi- with arm-linux-gnueabihf-:\"06-hf\"<\/a><\/li>\n
  11. Now we are ready to build Qt. Due to a bug in the Qmake build script, we will need to build it in 2 steps: first we will build a Qmake for Windows and then we’ll build the actual Qt binaries. First we will modify the win32-g++ platform definition to prevent MinGW from excluding some functions that Qt relies upon. Open the\u00a0qt-everywhere-opensource-src-5.5.0\\qtbase\\mkspecs\\win32-g++\\qmake.conf<\/strong> file and add -U__STRICT_ANSI__<\/strong> to CXXFLAGS:\"06a-strictansi\"<\/a><\/li>\n
  12. Now we can build the Windows tools. Create a directory (e.g. qt-build) and run the configuration script from there:\n
    mkdir qt-build\r\ncd qt-build\r\n..\/qt-everywhere-opensource-src-5.5.0\/configure -platform win32-g++ -xplatform linux-arm-gnueabi-g++ -release -opengl es2 -device linux-rasp-pi2-g++ -sysroot C:\/SysGCC\/Raspberry\/arm-linux-gnueabihf\/sysroot -prefix \/usr\/local\/qt5<\/pre>\n
    \"07-buildqmake\"<\/a>Note the “-opengl es2” option that configures Qt to use the Raspberry Pi framebuffer directly instead of the X11 system.<\/li>\n
  13. Eventually the build should fail complaining about the errors to process specs for the raspberry device:\"08-fail\"<\/a><\/li>\n
  14. This is normal as long as qmake.exe got built. Check this by running “qtbase\/bin\/qmake -v”:\"09-qmake\"<\/a><\/li>\n
  15. Now we can build the rest of the Qt framework. First of all open the qtbase\\configure<\/strong> file and replace the condition before the “Creating qmake line” with this one:\n
    if [ '!' -f \"$outpath\/bin\/qmake.exe\" ]; then<\/pre>\n
    \"10-configure\"<\/a><\/li>\n
  16. Start the configure script again, this time adding the following argument to the end of the previous command line:\n
    -device-option CROSS_COMPILE=C:\/SysGCC\/Raspberry\/bin\/arm-linux-gnueabihf- -qt-xcb<\/pre>\n
    \"11-configured\"<\/a>The -device-option is required when using the device specification, however if you specify it while building Qmake, the Qt build system will try to use the cross-compiler to build the Windows Qmake executable that will obviously fail.<\/p>\n
    If you get errors while configuring Qt, please check that:<\/p>\n