mraa  2.0.0
Low Level Skeleton Library for Communication on GNU/Linux platforms
Building libmraa

libmraa uses cmake in order to make compilation relatively painless. CMake runs build out of tree so the recommended way is to clone from git and make a build/ directory inside the clone directory.

For building imraa check Building mraa with imraa page.

Build dependencies

Not all these are required but if you're unsure of what you're doing this is what you'll need:

For Debian-like distros the below command installs the basic set:

1 sudo apt-get install git build-essential swig3.0 python-dev nodejs-dev cmake libjson-c-dev

Adjust as needed, for instance Python 3 builds will require python3-dev. On Ubuntu Bionic you'll need to downgrade node.js (see nodesource for some handy install scripts) or patch SWIG. This is explained more in the advanced dependencies list below.

Documentation dependencies

To build the documentation you'll also need:

Basic build steps

1 mkdir build
2 cd build
3 cmake ..
4 make

If this goes wrong and you have all the dependencies installed, then please file an issue with the full output of cmake .. and make or however far you got.

After that you can install built files (into default path) by running:

1 sudo make install

See flags for adjusting install paths in the section below.

Currently our install logic puts Python bindings into standard paths, which do not work on Debian due to their policy.

We are working on a permanent solution, in the meantime please use this command after make install to link installed modules where Debian's Python expects them:

1 sudo ln -s <your install prefix, e.g. /usr>/lib/python2.7/site-packages/* /usr/lib/python2.7/dist-packages

Same approach works for Python 3, you'll just need to adjust the version number in the path accordingly.

Configuration flags

Our CMake configuration has a number of options, cmake-gui or ccmake (cmake -i is no longer with us :() can show you all the options. A few of the more common ones are listed below. Note that when the option starts with CMAKE_ it's an option that is made available by CMake and will be similar in all CMake projects. You need to add them after cmake but before ..

A few recommended options:

Changing install path from /usr/local to /usr: -DCMAKE_INSTALL_PREFIX:PATH=/usr

Building debug build - adds -g and disables optimizations - this will force a full rebuild: -DCMAKE_BUILD_TYPE=DEBUG

Using clang instead of gcc: -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++

Building with an older version of SWIG (< 3.0.2) requires the disabling of JavaScript: -DBUILDSWIGNODE=OFF

Disabling Python module building: -DBUILDSWIGPYTHON=OFF

Building doc, this will require SPHINX & Doxygen: -DBUILDDOC=ON You will also require clone git submodules from your existing checkout: git submodule update --init --recursive Then from doxygen2jsdoc dir: npm install Then from doxyport dir: make setup

Override build architecture (this is useful because on x86 ARM code is not compiled so use this flag to force the target arch) -DBUILDARCH=arm

You can also enable -Wall for gcc before running cmake by exporting your wanted CC flags to the CC env var export CC="gcc -Wall"

Sometimes it's nice to build a static library, on Linux systems just set -DBUILD_SHARED_LIBS=OFF Note that for static builds the python bindings will not build as they would require a static python etc... You can try to link mraa statically to the python binding module by adding -fPIC with -DCMAKE_C_FLAGS=-fPIC. You can also use the node.js gyp build system to get node.js static bindings.

Dependencies continued

You'll need at least SWIG version 3.0.2 and we recommend 3.0.12 to build the JavaScript & Python modules. If your version of SWIG is older than this then please see above for disabling SWIGNODE. Otherwise you will get a weird build failure when building the JavaScript module. The Python module builds with SWIG 2.x but we don't test it.

JavaScript bindings for node.js 7.0.0+

Building the JavaScript bindings using the latest versions of node.js does involve additional steps due to our dependency on SWIG. In short, a patch is needed to compile correctly with node.js 7.0.0 or newer. We found the install scripts from nodesource to be very handy for switching versions and they support all versions of Ubuntu.

The patch applies cleanly on SWIG 3.0.12, available by default on Ubuntu Bionic and through 3rd party PPAs for older distributions. For example, with Xenial or Zesty you could use this.

To patch SWIG on Ubuntu (assumes you start in the home folder):

1 wget
2 cd /usr/share/swig3.0
3 sudo patch -p2 <~/0001-Add-Node-7.x-aka-V8-5.2-support.patch

Keep in mind that Ubuntu Bionic ships with node.js version 8. You'll need to either use the patch or downgrade node.js.

Build version

During the build, we'll assume you're building from git, note that if you compile with git installed your version of mraa will be versioned with git describe --tag to make it easy for identification. You can easily modify version.c in build/src. If you don't build from a git tree then you will simply have a version which matches the latest released version of mraa.

Using a Yocto/OE toolchain

In order to compile with a Yocto/OE toolchain use the following toolchain file. This works well on the Edison 1.7.2 SDK. First source the environment file, then use our CMake toolchain file.

1 source /opt/poky-edison/1.7.2/environment-setup-core2-32-poky-linux
2 mkdir build
3 cmake -DCMAKE_TOOLCHAIN_FILE=../cmake/Toolchains/oe-sdk_cross.cmake ..
4 make

Building Java bindings

Have JAVA_HOME set to JDK install directory. Most distributions set this from /etc/profile.d/ and have a way of switching between alternatives. We support both OpenJDK and Oracle's JDK. On Arch Linux with OpenJDK 8 you'll have to set this yourself like this:

1 export JAVA_HOME=/usr/lib/jvm/default/

Then use the CMake configuration flag: -DBUILDSWIGJAVA=ON To compile

1 javac -cp $DIR_WHERE_YOU_INSTALLED_MRAA/mraa.jar:.

To run, make sure is in LD_LIBRARY_PATH

1 java -cp $DIR_WHERE_YOU_INSTALLED_MRAA/mraa.jar:. Example

If you want to add or improve Java bindings for mraa, please follow the Creating Java Bindings Guide.

Building for the Android Things Peripheralmanager Client


The Android NDK contains a CMake find_package module FindAndroidThings.cmake. Make sure the directory containing this module is added to the CMAKE_MODULE_PATH.

Android NDK r14b

1 NDK_HOME="/path/to/android-ndk-r14b"
2 ANDROIDTHINGS_NATIVE_LIB="/path/to/native-libandroidthings-0.5.1-devpreview"
4 cmake -DBUILDSWIG=ON \
10  -DANDROID_PLATFORM=android-24 \
12  -DANDROID_STL=c++_shared \
17  -DCMAKE_FIND_ROOT_PATH=$NDK_HOME/platforms/android-24/arch-x86/ \
19  -DCMAKE_TOOLCHAIN_FILE=$NDK_HOME/build/cmake/android.toolchain.cmake \
21  ..

Building with Docker

You can use docker and docker-compose to generate a complete build environment for mraa without having to install any other tool.


NOTE: docker-compose is an optional requirement. It actually make running complex docker build and run command easier. But you can just use docker to build and run.

Using Docker Images to build Mraa

tl;dr: Just use this commands to build mraa:

1 # Build mraa documentation
2 $ docker-compose run doc
3 # Build mraa python2 package and run python2 tests
4 $ docker-compose run python2
5 # Build mraa python3 package and run python3 tests
6 $ docker-compose run python3
7 # Build mraa java package and run java tests
8 $ docker-compose run java
9 # Build mraa node4 package
10 $ docker-compose run node4
11 # Build mraa node5 package
12 $ docker-compose run node5
13 # Build mraa node6 package
14 $ docker-compose run node6
15 # Build mraa for android things package
16 $ docker-compose run android
17 # Run Sonar Qube Scans for mraa
18 $ docker-compose run sonar-scan

docker-compose will take a look at the docker-compose.yaml file in the repository root directory, pull the required docker image, and run an specific command to build mraa for the requested target. Once the build is completed, you will have a build/ folder in the repository root with all the compiled code. This build/ folder is created by using a docker volume. The build\ folder contents is reused each time you execute docker-compose run [TARGET]. To know more about volumes in Docker, visit the Docker Volume Documentation.

You can also start an interactive session inside the docker container if you need to run some custom build commands:

1 # Start an interactive bash shell inside the container
2 $ docker-compose run python2 bash
3 # From now, all the commands are executed inside the container
4 $ cd build && cmake -DBUILDSWIGPYTHON=ON .. && make clean all

If you don't want to use docker-compose, you can also use docker run to build mraa. For example, to build mraa for python2, you can do:

1 # From the repository root folder
2 $ docker run \
3  --volume=$(pwd):/usr/src/app \
4  --env BUILDSWIG=ON \
8  inteliotdevkit/mraa-python \
9  bash -c "./scripts/ && make -Cbuild _python2-mraa"

Proxy considerations

If, for some reason, you are behind a proxy, find below a list of common problems related to proxy settings:

docker cannot pull images from

Visit this link to configure docker daemon behind a proxy.

docker run fails to access the internet

Docker-compose will automatically take http_proxy, https_proxy, and no_proxy environment variables and use it as build arguments. Be sure to properly configure this variables before building.

Docker, unlike docker-compose, does not take the proxy settings from the environment automatically. You need to send them as environment arguments:

1 # From the repository root folder
2 $ docker run \
3  --volume=$(pwd):/usr/src/app \
4  --env BUILDSWIG=ON \
8  --env http_proxy=$http_proxy \
9  --env https_proxy=$https_proxy \
10  --env no_proxy=$no_proxy \
11  inteliotdevkit/mraa-python \
12  bash -c "./scripts/ && make -Cbuild _python2-mraa"