Raspberry Pi Beginners Guide

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Introduction

This is a step by step guide to help beginners to cross-compile Qt5 for the Raspberry Pi. This allows the you to be able to compile Qt5 applications for the Raspberry Pi from a PC and also deploy to the device automatically and debug programs. The instructions were tested on Ubuntu 15.04 but should work with any Debian based operating system.

This article will focus on simplicity, if you are looking for additional customization, please check a more detailed guide.

For a detailed tutorial on cross-compiling under Windows, see this tutorial.

For an up-to-date guide for cross-compiling Qt 5.6 targeting eglfs and Raspbian Jessie, see RaspberryPi2EGLFS.

Getting Started

First we create a folder to hold the source code and all the required files to do the cross-compilation. We chose to create a directory named "opt" in the home folder:

mkdir~/opt
cd~/opt

Now, download the following files:

• Raspbian Wheezy image from (here):

wget http://downloads.raspberrypi.org/raspbian_latest -O wheezy-raspbian-latest.zip
unzip wheezy-raspbian-latest.zip

And mount it:

 sudo mkdir /mnt/rasp-pi-rootfs
sudo mount -o loop,offset=62914560 2015-05-05-raspbian-wheezy.img /mnt/rasp-pi-rootfs

• Download the cross compiling toolchain:

wget https://www.dropbox.com/s/sl919ly0q79m1e6/gcc-4.7-linaro-rpi-gnueabihf.tbz
(or at http://de.sourceforge.jp/projects/sfnet_rfidmonitor/downloads/crosscompilation-resources/gcc-4.7-linaro-rpi-gnueabihf.tbz)
tar -xf gcc-4.7-linaro-rpi-gnueabihf.tbz

paulo@westeros:~/opt/qt5/qtimageformats$ It is a 32-bit build so if you are running on a 64-bit machine (you probably are) you need to install ia32-libs:

paulo@westeros:~/opt$ sudo apt-get install ia32-libs

* ia32-libs has been replaced with Multiarch. Try installing lib32z1 lib32ncurses5 lib32bz2-1.0 instead.

• Clone the cross-compile-tools repository:

This repository contains a script that will be used to fix some symbolic links.

 git clone https://git.milosolutions.com/other/cross-compile-tools.git

• Clone and init the Qt5 repository:

git clone git://code.qt.io/qt/qt5.git
cd qt5
./init-repository

If you're behind a firewall ./init-repository might fail. First run this command:

sed -i 's/git:/https:git./' .gitmodules

Then retry:

./init-repository -f

Compiling qtbase

Now the we have all the resources needed to compile qt5 for raspberry, we need to execute a script to fix symlinks and lib paths:

cd ~/opt/cross-compile-tools
sudo ./fixQualifiedLibraryPaths /mnt/rasp-pi-rootfs/ ~/opt/gcc-4.7-linaro-rpi-gnueabihf/bin/arm-linux-gnueabihf-gcc

Go to the qt5/qtbase folder and run:

./configure -opengl es2 -device linux-rasp-pi-g++ -device-option CROSS_COMPILE=~/opt/gcc-4.7-linaro-rpi-gnueabihf/bin/arm-linux-gnueabihf- -sysroot /mnt/rasp-pi-rootfs -opensource -confirm-license -optimized-qmake -reduce-exports -release -make libs -prefix /usr/local/qt5pi -hostprefix /usr/local/qt5pi
make -j 4
sudo make install

Note: if you want the qmlscene binary you should add -make tools to the ./configure command.

Compiling other modules

Now that you have qmake, you can cross-compile the other modules. To avoid dependencies errors, the following order is sugested: qtimageformats, qtsvg, qtjsbackend, qtscript, qtxmlpatterns, qtdeclarative, qtsensors, qt3d, qtgraphicaleffects, qtjsondb, qtlocation, qtdocgallery.

To compile, you must do like the example below:

paulo@westeros:~/opt/qt5$ cd qtimageformats
paulo@westeros:~/opt/qt5/qtimageformats$ /usr/local/qt5pi/bin/qmake .
paulo@westeros:~/opt/qt5/qtimageformats$ make -j4
paulo@westeros:~/opt/qt5/qtimageformats$ sudo make install

Transferring the changed image back onto SD Card

After completing the these instructions the Raspberry Pi image will have QT5 installed onto it now we can copy it to the sdcard using dd:

paulo@westeros:~/opt/qt5$ cd~/opt/
paulo@westeros:~/opt$ sync; sudo umount /mnt/rasp-pi-rootfs
paulo@westeros:~/opt$ sudo dd bs=1M if=2015-05-05-raspbian-wheezy.img of=/dev/sdb; sync

Note: Check the what the device name of your SD Card is by running the following command which will list the storage devices on your computer. Don't use the number at the end as that is the partition number and we're writing to the whole SD card:

sudo fdisk -l

Notes for macOS

• Because your sdcard will be partitioned, macOS won't let you umount it, so you'll need to type:

sudo diskutil umountDisk /dev/disk3

where "disk3" will be the /dev/diskXsY where your sdcard first appeared.

• To perform dd you will need to use the *r*disk index, so if your sdcard is disk3 you will need to type:

sudo dd bs=1M if=2015-05-05-raspbian-wheezy.img of=/dev/rdisk3; sync

Boot up your pi.

Configuring Qt Creator

To use Qt Creator properly, you must configure the "Qt Version" and "Tool Chains" sections.

Tool Chain Settings

go to Tools -> Options..-> Build & Run -> Compilers tab. click in "Add -> GCC". On "Compiler Path" set to "/home/<you>/opt/gcc-4.7-linaro-rpi-gnueabihf/bin/arm-linux-gnueabihf-g+". Name it "ARM GCC" or similar. obs: Adjust it to your username.

Qt Version settings.

Now go to Tools -> Options..-> Build & Run -> Qt Versions tab. Click in "Add.." and choose you qmake for raspberry "/usr/local/qt5pi/bin/qmake".

Note for macOS

• Because /usr is not visible by default, you first need to open a terminal and type:

sudo SetFile -a v /usr

• After you've completed the qmake selection, if you wish to make /usr invisible again, type the same command with a capital V :

sudo SetFile -a V /usr

An alternative is to use CMD+SHIFT+. (dot) in the file dialog to make invisible directories momentarily visible

Configure Linux Devices

Go to Tools -> Options…-> Devices -> Devices tab.

Add a new configuration setting a "Generic Linux Device" Hostname or IP address is the IP of your raspberry user is pi password is raspberry obs: if your not did change it.

Target Path

When you try to deploy a program on your Raspberry Pi from Qtcreator you may get an error about an unknown command. This is because Qtcreator does not know where to copy the compiled file onto the Raspberry Pi. The following line should be added to your .pro file:

target.path = /home/pi/

You may change the path to anything you want and the executable will be copied to and run from this location.

Now you are ready to run your first Qt raspberry pi project.

Example Project

You can download a hello world project:

paulo@westeros:~$ git clone https://git.gitorious.org/qt5-raspberrypi-example/qt5-raspberrypi-example.git

Open the project in Qt Creator and go to the Projects pane. Click Manage Kits and then Add. Fill in: Name: Raspberry Pi Device Type: Generic Linux Device Device: Raspberry Pi Compiler: ARM GCC Debugger->Manage->Edit->"/home/<you>/opt/gcc-4.7-linaro-rpi-gnueabihf/bin/arm-linux-gnueabihf-gdb" (change your username) Qt version: Qt 5.x.x (qt5pi) Ok->Add Kit->Raspberry Pi

Then go to the "Rasperry Pi" kit tab->System Environment and add LD_LIBRARY_PATH which is set to /usr/local/qt5pi/lib

Now you can build and run your application from Qt Creator.

Troubleshooting

Qt version not properly installed

You need to keep the SD card image mounted during development! Use this command in the same folder as the .img file:

sudo mount -o loop,offset=62914560 2015-05-05-raspbian-wheezy.img /mnt/rasp-pi-rootfs

If QtCreator still reports this after mounting the SD card image, then you may need to create the directories missing from

/mnt/rasp-pi-rootfs/usr/local/qt5pi/

or whatever the mount path is (these will probably include bin, translations, and so on). You can create empty directories using the mkdir command.

The default mkspec symlink is broken.

It means that mkspec is not found on your sysroot, so your must copy it.

paulo@westeros:~$ sudo cp -r /usr/local/qt5pi/mkspecs/ /mnt/rasp-pi-rootfs/usr/local/qt5pi/

If the problem persists, create the missing symlink, e.g.

sudo ln -s /usr/local/qt5pi/mkspecs/devices/linux-rasp-pi-g''+ /usr/local/qt5pi/mkspecs/default

It is probably a good idea to do the same for the sysroot mkspecs.

Include <QtGui/QtGui>: No such file or directory

It seems Qt's include was not found and you must add it to you .pro file:

INCLUDEPATH += /mnt/rasp-pi-rootfs/usr/local/qt5pi/include/

cc1: fatal error...

cc1: fatal error: .pch/release-shared/QtGui: No such file or directory

Some people have seen this error. Adding the "-no-pch" option when running configure should prevent it.

Getting Could not determine...

Getting Could not determine the target architecture! and Could not determine the host architecture!

If you are getting this kind of error, it is possible that your current git branch is something other than master. To be sure, do the following:

daniel@daniel-t3500 : ~/opt/qt5/qtbase $ git branch

If it shows like this:

* (no branch)
 master

Then you must checkout to master branch before running ./configure:

daniel@daniel-t3500 :~/opt/qt5/qtbase $ git checkout master
daniel@daniel-t3500 : ~/opt/qt5/qtbase $ git branch
* master

It is also good to fetch the latest commits and apply them by doing:

daniel@daniel-t3500 :~/opt/qt5/qtbase $ git pull

Also, check for the installation of libz (32 bits) in yor system. In ubuntu (64 bits) you might just:

sudo apt-get install lib32z1-dev

After the ./configure script has failed first run these commands before restarting ./configure:

daniel@daniel-t3500 : ~/opt/qt5/qtbase $ git reset —hard
daniel@daniel-t3500 :~/opt/qt5/qtbase $ git git clean -dxf

EGL Error : Could not create...

EGL Error : Could not create the egl surface: error = 0x3000

Try allocating more memory to video (try 64 or 128MB). Use the raspi-config utility to change this.

pi@raspberrypi ~ $ sudo raspi-config

ABI detection failed

You will need Qt Creator 2.6 for Qt5 up to and including beta2. Any Qt 5 later than that will need to use nightly snapshots (or will have to wait for Qt Creator 2.6.1): After the beta2 all libraries were renamed again.

See this forum thread for more details

./configure: 2654: ./configure...

./configure: 2654: ./configure: /home/<you>/opt/gcc-4.7-linaro-rpi-gnueabihf/bin/arm-linux-gnueabihf-g: not found -reduce-exports was requested but this compiler does not support it

The error message is totally misleading. The real cause is that the precompile toolchain is 32-bit, so you need to:

sudo apt-get install ia32-libs

make: g: Command not found

Qt requires a native (non-cross-compiling) copy of g+ to be installed in order to build qmake. You can't use clang. Fix with:

sudo apt-get install build-essential

In function `dlopen'...

/mnt/rasp-pi-rootfs/usr/lib/arm-linux-gnueabihf/libdl.a(dlopen.o): In function `dlopen': (.text+0xc): undefined reference to `__dlopen'

You need to run the ./fixQualifiedLibraryPaths again.

See: http://stackoverflow.com/questions/13626726/an-error-building-qt-libraries-for-the-raspberry-pi for more info.

cc1: fatal error...

cc1: fatal error: .pch/release-shared/Qt5Gui: No such file or directory

Try adding -no-pch to the ./configure command line.

Cannot create forwarding script...

Cannot create forwarding script Betrete 'qtactiveqt'.git/hooks/commit-msg: Datei oder Verzeichnis nicht gefunden

Try:

unset LANG
./init-repository -f