This is a very minimal pass at a workflow that can use a custom toolchain to create a ROS2 build.

It cannot handle dependencies that are outside the source tree, so there is only a limited subset of ROS2 that this can build.

As of right now, it is specifically tuned to using a linaro aarch64 cross compiler, but to make it generic should not take much modification.

You need to have Docker and vcs installed on your dev computer already

1. Download the linaro cross compiler (6.5)
   • https://releases.linaro.org/components/toolchain/binaries/6.5-2018.12/aarch64-linux-gnu/gcc-linaro-6.5.0-2018.12-x86_64_aarch64-linux-gnu.tar.xz
   • extract it fully into this repo and change the directory's name to gcc-linaro-aarch64/
2. Download the linaro sysroot (6.5)
   • https://releases.linaro.org/components/toolchain/binaries/6.5-2018.12/aarch64-linux-gnu/sysroot-glibc-linaro-2.23-2018.12-aarch64-linux-gnu.tar.xz
   • extract it fully into this repo and change the directory's name to sysroot-linaro6.5
3. Get the ROS2 sources

vcs import src < minimal_cpp_ros2_master.repos
# we do not have log4cxx dependency and don't actually need it
touch src/ros2/rcl_logging/rcl_logging_log4cxx/COLCON_IGNORE

Start the container from the top dir of this repo

docker run -it -v $(pwd):/ws/ros2build candleends/ros2_cross_compiler

Now run the build within the container

colcon build --mixin aarch64-linux --packages-up-to demo_nodes_cpp

Exit the build container. The install/ directory is your ROS2 build.

adb push install /userdata/install

Open one adb shell to the device

export LD_LIBRARY_PATH=/userdata/install/lib
/userdata/install/lib/demo_nodes_cpp/talker

Then, in a second adb shell

export LD_LIBRARY_PATH=/userdata/install/lib
/userdata/install/lib/demo_nodes_cpp/listener

Now, you should see that the listener is receiving messages from the talker.

If you need to change the docker image that we use for building, it's easy to rebuild

cd docker
docker build . -t candleends/ros2_cross_compiler