This information is for developers who want to get involved with openhatd.

Operating system compatibility

openhatd is designed to be platform-independent and portable between C++ compilers. It works with recent MSVCs and GCCs that support the C++11 standard (g++ 4.9 and newer). There are currently some problems with clang that might eventually be worked out.

Different operating systems provide different advantages when developing or compiling openhatd:

  • Windows: Good tooling (Visual Studio 2015 Community Edition provides an excellent debugger). Well suited for development and testing.
  • Linux: Good toolchains, but debugger support is somewhat basic. Good for tests, static analysis, and cross-compiling, or trying different compilers. Linux specific development, obviously, must be done here.
  • Raspberry Pi: Suitable for production use, but less for development. OK for developing specific plugins which compile reasonably well on the Pi.

Windows and Raspberry Pi binaries are standalone, statically linked. Linux binaries cannot be statically linked due to problems with glibc; therefore, they are dynamically linked and release builds contain the necessary libraries.

openhatd uses continuous integration platforms Travis CI for Linux releases and AppVeyor for Windows releases. When pushing commits or merging pull requests continuous integration will automatically build the project, run tests, build documentation and upload everything to the server.

Releases do not contain debug information. For debugging on Windows, set the configuration to "Debug". On Linux, the environment variable DEBUG must be set to 1 when invoking make, such as

$ DEBUG=1 make

Building openhatd

It is recommended to build openhatd on Linux. Any modern Linux will probably be fine. openhatd builds at least on Debian 8 (Jessie), Linux Mint 17, and Ubuntu 16. If you develop platform independent code, if you need the convenience of the Visual Studio debugger, or if you simply prefer Windows, you can also develop for openhatd using Visual Studio 2015 or newer.

Cloning the OpenHAT repository will pull in most dependencies via submodules. Obtain the code from Github using the following command:

$ git clone --recursive

To manually download the submodules use:

$ git submodule update --init --recursive

The submodule opdi_core in turn includes the submodule POCO which you have to build first. For instructions please see the file opdi\_core/code/c/libraries/POCO\_patches/readme.txt.

You have to copy the content of the opdi_core/code/c/libraries/POCO_patches folder over to the opdi_core/code/c/libraries/POCO folder before using one of the provided scripts (build_poco*.sh) to build the libraries.

Building on Linux

On Linux, you need to install the prerequisites for the documentation first (see below: Building the documentation).

To build openhatd, go to the folder openhatd and issue

$ make

First, plugins will be built, then the main program. This will also create a current release tarball. To run a number of tests, issue

$ make tests

Cross-compiling on Linux

openhatd provides makefiles for cross-compiling to armhf and i386.


To setup the armhf cross-compiling environment (assuming a 64 bit machine), go to your home directory and issue:

git clone --depth=1
export PATH=$(pwd)/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin:$PATH

From the directory opdi_core/code/c/libraries/POCO, do:


This will cross-compile the POCO libraries for armhf.

To build openhatd for armhf, go to openhatd/src and issue:

make -f makefile-rpicc


Building openhatd for 32 bit Linux required additional packages:

sudo apt-get install gcc-multilib g++-multilib linux-libc-dev:i386

From the directory opdi_core/code/c/libraries/POCO, do:


This will cross-compile the POCO libraries for i386.

To build openhatd for i386, go to openhatd/src and issue:

make -f makefile-i386

Building on Windows

Open the Visual Studio solution file openhatd/openhatd.sln. Build the solution. To run the program from within Visual Studio, go to the openhatd project's properties and enter -c hello-world.ini as command line parameter for debugging. Press F5 (debug) or Ctrl+F5 to run the program.

Building the documentation

Building the documentation requires Python, the Python package installer pip and Doxygen with the graphvizpackage.

On Linux:

$ sudo apt-get install python python-pip doxygen graphviz

Additionally required Python modules are setuptools, mkdocs and markdown_include:

$ sudo pip install setuptools 
$ sudo pip install mkdocs 
$ sudo pip install markdown_include

From within the openhatd folder, first build the Doxygen documentation:

$ doxygen Doxyfile

Then, build the mkdocs documentation:

$ mkdocs build

The configuration files for these documentations contain placeholders for version and timestamp. The makefile within the src folder contains logic to replace these placeholders when the docs target is invoked. This way is intended for releases only. If documentation generation fails the replaced versions of the files will remain in the openhatd folder; they then need to be reset with git checkout. For this reason it is recommended to invoke make release only if a previous documentation generation has completed successfully.


Ideally, testing is done on the target hardware with external components connected. Unfortunately, this is not possible with continuous integration.

openhatd supports a test mode switched on by the command line flag -t. If this flag is set openhatd goes through the port initialization and configuration phase, then exits with code 0. Any error during these phases will fail the continuous integration tests (all configuration files supplied with an openhatd release should be at least checked with -t to ensure that they are free of superficial errors). This method only tests configuration file integrity and the correct operation of the startup phases. It does, however, not support functional testing and is therefore not a reliable indicator whether a build is free of certain bugs or not.

To test port state integrity and check for regressions you can use Test ports. Test ports are Digital ports that, when switched to High, perform regular tests on port properties. You can define an arbitrary number of Test ports, however, for automated tests there should be at least one test that terminates the program after it has been executed. Automatic tests are stored in the testconfigs/automatic directory and are not intended to be included in a release. If you provide new features or bug fixes please add a test case if possible.

Versioning and compatibility

Releases of openhatd follow the versioning scheme MAJOR.MINOR.PATCH:

The MAJOR component increases with very major changes in program architecture and/or release status.

The MINOR component is increased when additional features are added that may break backwards compatibility with existing plugins. A different MINOR number likely means that the Application Binary Interface (ABI), probably the memory layout of the important classes, has changed. It is not safe to use versions of plugins which have been compiled against a different MINOR number. This situation may result in inexplicable errors or strange behavior.

The PATCH component increases when bugs are fixed or new functions are added without changing the ABI. Plugins with a different PATCH number are safe.

Currently there is a limitation that the versioning components may be one-digit numbers only. (This may change when switching to C++14.)

Development and release branches

Development of new features takes place on the master branch of the Git repository. Whenever a new version is released a Git branch is made with this version number and the version number on the master branch is advanced. Fixes on the version branches require the creation of a patch tag with an increased patch number. New features are not to be implemented in already released versions.