RPI: Using lib bcm2835 from qt

[Drazz]

Hello,

I would like to understand better what I am doing when I install qt cross compile in Ubuntu for Raspbian buster.

I've installed in my raspberry bcm2835 lib like this:

tar zxvf bcm2835-1.xx.tar.gz
cd bcm2835-1.xx
./configure
make
sudo make check
sudo make install

I don't know where this lib has installed, but if I run:

sudo find / bcm2835 | grep bcm2835

I find files in:

/sys/...
/usr/include/linux/bcm2835-isp.h
/usr/src/linux-headers-5.10.17+/....
/usr/local/include/bcm2835.h
/usr/local/lib/libbcm2835.a
/lib/modules/ ....

Now from ubuntu, I run:

rsync -avz --rsync-path="sudo rsync" pi@192.168.1.60:/lib sysroot
rsync -avz --rsync-path="sudo rsync" pi@192.168.1.60:/usr/include sysroot/usr
rsync -avz --rsync-path="sudo rsync" pi@192.168.1.60:/usr/lib sysroot/usr
rsync -avz --rsync-path="sudo rsync" pi@192.168.1.60:/opt/vc sysroot/opt

Questions:

1. Would I be able to #include <bcm2835.h> from Qt Creator in Ubuntu with my raspberry pi kit? The lib is /usr/local/include/bcm2835.h but /usr/local does not get rsync.
2. Do I have to build again qt-everywhere and install? I have to do it every new lib I add?
3. Extra: How can I know where make install files are deployed?

Thank you

[jsulm]

@Drazz

1. Yes, if you sync your sysroot
2. No, only if Qt itself requires that lib
3. You should see that when you call make install. You can also check generated Makefiles

[Drazz]

After doing:

rsync -avz --rsync-path="sudo rsync" pi@192.168.1.60:/lib sysroot
rsync -avz --rsync-path="sudo rsync" pi@192.168.1.60:/usr/include sysroot/usr
rsync -avz --rsync-path="sudo rsync" pi@192.168.1.60:/usr/lib sysroot/usr
rsync -avz --rsync-path="sudo rsync" pi@192.168.1.60:/opt/vc sysroot/opt

Qt Creator from Ubuntu does not find <bcm2835.h>

This is my output when I sudo make install my lib:

/bin/mkdir -p '/usr/local/lib'
 /usr/bin/install -c -m 644  libbcm2835.a '/usr/local/lib'
 ( cd '/usr/local/lib' && ranlib libbcm2835.a )
 /bin/mkdir -p '/usr/local/include'
 /usr/bin/install -c -m 644 bcm2835.h '/usr/local/include

I've tried this with out success:

rsync -avz --rsync-path="sudo rsync" pi@192.168.1.60:/usr/local sysroot/usr/

I have my header in: sysroot/usr/local/include/bcm2835.h

[jsulm]

@Drazz You posted before this: /usr/local/include/bcm2835.h
So, you need to sync /usr/local

[jsulm]

@Drazz said in RPI: Using lib bcm2835 from qt:

I've tried this with out success

What does this mean? What happened?

[Drazz]

@jsulm said in RPI: Using lib bcm2835 from qt:

What does this mean? What happened?

I've #include <bcm2835.h> in a Qt project. Build fails because It doesn't find the lib.

[jsulm]

@Drazz I was asking about:
I've tried this with out success:

rsync -avz --rsync-path="sudo rsync" pi@192.168.1.60:/usr/local sysroot/usr/

Som what happened?

[Drazz]

@jsulm said in RPI: Using lib bcm2835 from qt:

@Drazz I was asking about:
I've tried this with out success:
rsync -avz --rsync-path="sudo rsync" pi@192.168.1.60:/usr/local sysroot/usr/
Som what happened?

Now, In my Ubuntu I have this:

/opt/qt5pi/sysroot/usr/local/include/bcm2835.h
/opt/qt5pi/sysroot/usr/local/lib/libbcm2835.a

I open Qt Creator in my Ubuntu, select one random project and add in main.cpp

#include <bcm2835.h>

Build error:

../lifeRaspberry/main.cpp:18:21: fatal error: bcm2835.h: No such file or directory
 #include <bcm2835.h>
                     ^
compilation terminated.

[jsulm]

@Drazz You should add /usr/local/include folder to the include folders in your pro file. https://doc.qt.io/qt-5/qmake-variable-reference.html#includepath

[Drazz]

@jsulm said in RPI: Using lib bcm2835 from qt:

@Drazz You should add /usr/local/include folder to the include folders in your pro file. https://doc.qt.io/qt-5/qmake-variable-reference.html#includepath

Worked.

Final thought... why do I have to include the path? Does libraries that are in sysroot/usr/include need to include path?
If I rsync my raspberry pi /usr/local with my ubuntu sysrooot/usr, I would be able to quit that INCLUDE path from my .pro?

Thanks a lot for you time.

[jsulm]

@Drazz /usr is automatically searched by tools like compiler. But /usrLocal is not, so you have to tell the compiler to also look there.
"If I rsync my raspberry pi /usr/local with my ubuntu sysrooot/usr, I would be able to quit that INCLUDE path from my .pro?" - if you sync to /usr instead of /usr/local then there is no need to add anything to include paths.