07-xc-ros.md

Guide to Cross Compilation for a Raspberry Pi

1. Start
2. Setup XCS and RPi
3. Setup RPi Network and SSH
4. Setup RPi Peripherals
5. Setup Cross-compile environment
6. Cross-compile and Install Userland
7. Cross-compile and Install OpenCV
8. > Cross-compile and Install ROS
9. Compile and Install OpenCV
10. Compile and Install ROS
11. Remote ROS (RPi node and XCS master)
12. ROS package development (RPi/XCS)
13. Compile and Install WiringPi

8. Cross-compile and Install ROS

TO BE UPDATED. GUIDE MIGHT STILL WORK.

Before continuing, please make sure you followed the steps in:

• Setup
• Network/SSH
• crosscompile environment

In this document the steps for crosscompiling ROS are described.

Required Packages

As ROS has its own package-management system and eco system, multiple dependencies need to be installed on both the RPi and the VM. The VM requires foremost Python packages to process ROS dependencies, whereas the RPi requires additional information-processing libraries.

1. Install packages

   XCS~$ sudo apt-get install python-rosdep python-rosinstall-generator python-wstool python-rosinstall python-empy
   XCS~$ ssh rpizero-local
   RPI~$ sudo apt-get install pkg-config python2.7 python-dev python-pip sbcl libboost-all-dev libtinyxml-dev libgtest-dev liblz4-dev libbz2-dev libyaml-dev python-nose python-empy python-netifaces python-defusedxml
   RPI~$ sudo pip install -U rospkg catkin_pkg
   

   The call to sudo apt-get install on the RPi might take a while as approximately 250Mb extracted and installed. Installing rospkg and catkin_pkg may produce several errors when building yaml support while finishing gracefully. My guess is that all might be fine, but perhaps some future tests might show some issues.

2. Sync RPi libs to VM

   XCS~$ ~/rpicross_notes/scripts/sync-rpi-xcs.sh
   

Compilation

As mentioned before, the use of rsync results in broken symlinks. Hence we need to restore the ones required for ROS:

1. Restore symlinks after syncing

   When using the sync-scripts, this step can be omitted.

   XCS~$ ln -sf /home/pi/rpi/rootfs/lib/arm-linux-gnueabihf/librt.so.1 /home/pi/rpi/rootfs/usr/lib/arm-linux-gnueabihf/librt.so
   XCS~$ ln -sf /home/pi/rpi/rootfs/lib/arm-linux-gnueabihf/libbz2.so.1.0 /home/pi/rpi/rootfs/usr/lib/arm-linux-gnueabihf/libbz2.so
   XCS~$ ln -sf /home/pi/rpi/rootfs/usr/lib/arm-linux-gnueabihf/libpython2.7.so.1.0 /home/pi/rpi/rootfs/usr/lib/arm-linux-gnueabihf/libpython2.7.so
   

2. ROS uses gtest for several tests. The apt-get call for libgtest-dev only installs the source for gtest, therefore we need to crosscompile it for ourselfs to generate the libraries, using rpi-generic-toolchain.

   XCS~$ mkdir -p ~/rpi/build/gtest
   XCS~$ cd ~/rpi/build/gtest
   XCS~$ cmake \
      -D CMAKE_TOOLCHAIN_FILE=/home/pi/rpicross_notes/rpi-generic-toolchain.cmake \
      /home/pi/rpi/rootfs/usr/src/gtest
   XCS~$ make
   XCS~$ mv *.a /home/pi/rpi/rootfs/usr/lib
   

   SOURCE: https://www.eriksmistad.no/getting-started-with-google-test-on-ubuntu/ There is not make install so the generated libraries need to be copied manually to the appropriate folder.

3. We also need an utility called console_bridge, which we compile and install from source too. Again we use rpi-generic-toolchain.

   XCS~$ cd ~/rpi/src
   XCS~$ git clone https://github.com/ros/console_bridge
   XCS~$ mkdir -p ~/rpi/build/console_bridge
   XCS~$ cd ~/rpi/build/console_bridge
   XCS~$ cmake \
       -D CMAKE_TOOLCHAIN_FILE=/home/pi/rpicross_notes/rpi-generic-toolchain.cmake \
       /home/pi/rpi/src/console_bridge
   XCS~$ make
   XCS~$ make install DESTDIR=/home/pi/rpi/rootfs
   

4. After installing all dependencies, init rosdep.

   XCS~$ sudo rosdep init
   XCS~$ rosdep update
   

5. Create catkin workspace for the RPi-builds.

   Note that this workspace is not located in the ~/rpi or ~/rpi/rootfs directories. Because ROS comes with its own environment management system, a seperate directory is created which is synced with the RPi in a similar way as rootfs. Most important is that the path of the workspace in the VM equals (/home/pi/ros/src_cross) the path to which the workspace is synchronised on the RPi (which will be /home/pi/ros/src_cross).

   XCS~$ mkdir -p ~/ros/src_cross
   XCS~$ cd ~/ros/src_cross
   

6. Download ROS core packages and init workspace

   XCS~$ rosinstall_generator ros_comm --rosdistro kinetic --deps --wet-only --tar > kinetic-ros_comm-wet.rosinstall
   XCS~$ wstool init -j8 src kinetic-ros_comm-wet.rosinstall
   

7. Build ROS

   XCS~$ ./src/catkin/bin/catkin_make_isolated \
       -DCMAKE_BUILD_TYPE=Release \
       -DCMAKE_TOOLCHAIN_FILE=/home/pi/rpicross_notes/rpi-generic-toolchain.cmake
   

   This creates two folders: devel_isolated and build_isolated of which the latter can be ignored.

Adding packages after building ROS

When additional ros-packages are needed, but ROS is already build, the following steps can be taken:

1. Goto the crosscompilation catkin-workspace:

   XCS~$ cd ~/ros/src_cross
   

2. Use rosinstall_generator to create an additional .rosinstall, including the specified package(s). E.g sensor_msgs:

   XCS~$ rosinstall_generator sensor_msgs --rosdistro kinetic --deps --wet-only --tar > sensor_msgs.rosinstall
   

3. Merge the file with the existing .rosinstall and update ROS it's source tree

   XCS~$ wstool merge -t src sensor_msgs.rosinstall
   XCS~$ wstool update -t src
   

4. Finally, rebuild ROS

   XCS~$ ./src/catkin/bin/catkin_make_isolated \
       -DCMAKE_BUILD_TYPE=Release \
       -DCMAKE_TOOLCHAIN_FILE=/home/pi/rpicross_notes/rpi-generic-toolchain.cmake
   

Synchronisation

In addition to updates of rootfs we also need to synchronise src_cross.

Starting with rootfs:

1. Use a direct call:

   XCS~$ sudo rsync -auHWv --no-perms --no-owner --no-group /home/pi/rpi/rootfs/ rpizero-local-root:/
   

2. Or use the link-correcting script:

   XCS~$ /home/pi/rpicross_notes/scripts/sync-xcs-rpi.sh
   

And for ~/ros/src_cross:

1. Use a direct call:

   XCS~$ rsync -auHWv --no-perms --no-owner --no-group /home/pi/ros/src_cross/devel_isolated rpizero-local:/
   XCS~$ rsync -auHWv --no-perms --no-owner --no-group /home/pi/ros/src_cross/src rpizero-local:/
   

   Which copies both devel_isolated and src from /home/pi/ros/src_cross/* (VM) to /home/pi/ros/src_cross/* (RPi)

2. Or use this script:

   XCS~$ /home/pi/rpicross_notes/scripts/sync-ros.sh
   

3. Unfortunatly ROS includes the path to rootfs and subsequent libraries in its binairies. To enable ROS on the RPi to find the proper libraries, a symbolic link is created, simulating the path to rootfs

   XCS~$ ssh rpizero-local
   RPI~$ mkdir -p /home/pi/rpi
   RPI~$ ln -s / /home/pi/rpi/rootfs
   

Testing

Testing the compiled ROS-libraries and catkin workspace

Prerequisites:

• Toolchain installed
• ROS compiled & synced

Steps:

1. Set bash to use the crosscompile-ros settings

   XCS~$ source ~/rpicross_notes/scripts/ros_cross
   

   ROS biniaries such as catkin_make are actually python scripts. Therefore we can use several libraires/scripts from the crosscompiled workspace on both the RPi and VM.

2. Cross-compile the helloros code with the toolchain in this repositiory.

   XCS~$ mkdir -p ~/rpi/build/hello/ros
   XCS~$ cd ~/rpi/build/hello/ros
   XCS~$ cmake \
       -D CMAKE_TOOLCHAIN_FILE=/home/pi/rpicross_notes/rpi-generic-toolchain.cmake \
       ~/rpicross_notes/hello/ros/
   XCS~$ make
   

   Note that the toolchain sets the proper path for pkg-config (/home/pi/ros/src_cross/devel_isolated) to find XXXConfig.cmake files for ROS.

3. Transfer helloros to the RPi (located in devel/lib/helloros)

   XCS~$ scp devel/lib/helloros/helloros rpizero-local:~/
   

4. Connect two terminals with the RPi

   1. Launch roscore in the first

      XCS~$ ssh rpizero-local
      RPI~$ source ~/ros/src_cross/devel_isolated/setup.bash
      RPI~$ roscore
        ... logging to /home/pi/.ros/log/9d57fc26-0efa-11e7-97cb-b827eb418803/roslaunch-rpizw-hessel.local-893.log
        Checking log directory for disk usage. This may take awhile.
        Press Ctrl-C to interrupt
        Done checking log file disk usage. Usage is <1GB.
      
        started roslaunch server http://rpizw-hessel.local:42774/
        ros_comm version 1.12.7
      
      
        SUMMARY
        ========
      
        PARAMETERS
         * /rosdistro: kinetic
         * /rosversion: 1.12.7
      
        NODES
      
        auto-starting new master
        process[master]: started with pid [911]
        ROS_MASTER_URI=http://rpizw-hessel.local:11311/
      
        setting /run_id to 9d57fc26-0efa-11e7-97cb-b827eb418803
        process[rosout-1]: started with pid [924]
        started core service [/rosout]
      

   2. Launch helloros in the second

      XCS~$ ssh rpizero-local
      RPI~$ source ~/ros/src_cross/devel_isolated/setup.bash
      RPI~$ ./helloros
        [ INFO] [1490185604.127013218]: hello world 0
        [ INFO] [1490185604.226970277]: hello world 1
        [ INFO] [1490185604.326862336]: hello world 2
        [ INFO] [1490185604.426858394]: hello world 3
        ...
      

Code for this test is partially taken from http://wiki.ros.org/ROS/Tutorials/WritingPublisherSubscriber(c%2B%2B)