TipsAndTricks/Creating Recipes for ROS modules
Introduction
Robot Operating System (ROS) isn't an OS but a set of modules for robotics applications that interact via a pub/sub interface. Thanks to meta-ros you can add a wide range of ROS modules to your OS build. But how do you add your own ROS module? This article covers creating a recipe for a ROS module. For this article we'll use the vectornav module as an example. We'll also assume you already have meta-ros in your bblayers.conf.
Starting with "devtool add"
Standard practice for a creating a recipe is use devtool add. The github project doesn't have any releases, so let's use the git repo.
$ devtool add https://github.com/dawonn/vectornav
This completes OK, let's take a look at the recipe.
$ devtool edit-recipe vectornav
# Recipe created by recipetool # This is the basis of a recipe and may need further editing in order to be fully functional. # (Feel free to remove these comments when editing.) # WARNING: the following LICENSE and LIC_FILES_CHKSUM values are best guesses - it is # your responsibility to verify that the values are complete and correct. LICENSE = "MIT" LIC_FILES_CHKSUM = "file://vnccpplib/LICENSE.txt;md5=a3e2f266f2adb30b4ae17db437fa9727" SRC_URI = "git://github.com/dawonn/vectornav;protocol=https" # Modify these as desired PV = "1.0+git${SRCPV}" SRCREV = "497173f3ddbe21216d77d3b2021a5ef48a17ec4a" S = "${WORKDIR}/git" # NOTE: unable to map the following CMake package dependencies: catkin inherit cmake # Specify any options you want to pass to cmake using EXTRA_OECMAKE: EXTRA_OECMAKE = ""
Note the comment
# NOTE: unable to map the following CMake package dependencies: catkin
And sure enough, the build fails as the comment predicted.
$ devtool build vectornav | CMake Error at CMakeLists.txt:7 (find_package): | By not providing "Findcatkin.cmake" in CMAKE_MODULE_PATH this project has | asked CMake to find a package configuration file provided by "catkin", but | CMake did not find one.
Assuming you've worked with ROS, you'll know that it builds with a cmake based tool called catkin. This is usually installed as a developer package so some Yocto work will need to be done to "build the builder". This seems like a tough task, so let's see how other ROS modules have done this.
Understanding Existing ROS Recipes
Recipe Structure
Let's look at a an existing meta-ros recipe zeroconf-msgs to see how they support catkin.
DESCRIPTION = "General ros communications used by the various zeroconf implementations." SECTION = "devel" LICENSE = "BSD" LIC_FILES_CHKSUM = "file://package.xml;beginline=8;endline=8;md5=5ee5b8b046ae48ad94a2037ca953a67b" DEPENDS = "std-msgs message-generation" SRC_URI = "https://github.com/stonier/${ROS_SPN}/archive/${PV}.tar.gz;downloadfilename=${ROS_SP}.tar.gz" SRC_URI[md5sum] = "38e89e637f855c2ea0e8cb65c02dfd08" SRC_URI[sha256sum] = "a5bfd788bc2e2aefb07cb3a302a25cbeef2ce7e931a3a273cb1ae9669645a696" S = "${WORKDIR}/${ROS_SP}" inherit catkin
A few things to note
- The directive inherit catkin includes bitbake logic and it's a reasonable guess that this does all the catkin stuff just as inherit cmake enables cmake.
- As package.xml if referred to by LIC_FILES_CHKSUM must include some licence info. Let's dig into this.
- How are the DEPENDS defined? Let's dig into this as well.
Getting meta-data from package.xml
Let's take a look at it
<package> <name>zeroconf_msgs</name> <version>0.2.1</version> <description> General ros communications used by the various zeroconf implementations. </description> <maintainer email="d.stonier@gmail.com">Daniel Stonier</maintainer> <license>BSD</license> <url type="website">http://www.ros.org/wiki/zeroconf_msgs</url> <url type="repository">https://github.com/stonier/zeroconf_msgs</url> <url type="bugtracker">https://github.com/stonier/zeroconf_msgs/issues</url> <author email="d.stonier@gmail.com">Daniel Stonier</author> <buildtool_depend>catkin</buildtool_depend> <build_depend>message_generation</build_depend> <build_depend>std_msgs</build_depend> <run_depend>message_runtime</run_depend> <run_depend>std_msgs</run_depend> <export> <architecture_independent/> </export>in the <tt>run_depend</tt> that are not also in <tt> </package>
There is some useful information to create a recipe. Let's create a mapping between package.xml tags and recipe variables.
package.xml Tag | Recipe directive | Comment |
name | PN | This is defined by recipe filename |
version | PV | Usually defined by recipe filename |
description | SUMMARY | This should map to SUMMARY, not DESCRIPTION which adds detail |
license | LICENSE | Use package.xml for LIC_FILES_CHKSUM |
url | HOMEPAGE | type="website". Seems to be an optional tag |
url | SRC_URI | type="repository". Seems to be an optional tag |
buildtool_depend | inherit | Will always be catkin(?), which inherits cmake |
build_depend | DEPENDS | 1. Append to any values created by devtool
2. If ROS module name contains an underscore, convert to a dash |
runs_depend | RDEPENDS_{PN} | This should only contain entries that are not already in build_depend |
Putting it all together
So let's take a look at the package.xml for our module
<package> <name>vectornav</name> <version>0.1.0</version> <description>ROS interface for the VectorNav INS/GPS</description> <maintainer email="dereck@gmail.com">Dereck Wonnacott</maintainer> <license>MIT</license> <!-- <url type="website">http://ros.org/wiki/vectornav</url> --> <author email="dereck@gmail.com">Dereck Wonnacott</author> <buildtool_depend>catkin</buildtool_depend> <build_depend>roscpp</build_depend> <build_depend>geometry_msgs</build_depend> <build_depend>sensor_msgs</build_depend> <build_depend>tf</build_depend> <run_depend>roscpp</run_depend> <run_depend>sensor_msgs</run_depend> <run_depend>geometry_msgs</run_depend> <run_depend>tf</run_depend> <!-- Maintainer Note: The vnccpplib directory is from http://www.vectornav.com/support/downloads I removed the version string from the directory name, sanitized file permissions, and removed all but the src and include directories. --> </package>
And map it to recipe directives
PV | 0.1.0 |
SUMMARY | ROS interface for the VectorNav INS/GPS |
LICENSE | MIT |
HOMEPAGE | http://ros.org/wiki/vectornav |
inherit | catkin |
DEPENDS | roscpp geometry-msgs sensor-msgs tf |
Now let's update the recipe the devtool created with these values
SUMMARY = "ROS interface for the VectorNav INS/GPS" HOMEPAGE = "http://ros.org/wiki/vectornav" LICENSE = "MIT" LIC_FILES_CHKSUM = "file://package.xml;md5=5431059e1a277b5a31f4ad759bc9c76d \ file://vnccpplib/LICENSE.txt;md5=a3e2f266f2adb30b4ae17db437fa9727" SRC_URI = "git://github.com/dawonn/vectornav;protocol=https" PV = "0.1.0" SRCREV = "497173f3ddbe21216d77d3b2021a5ef48a17ec4a" DEPENDS = "roscpp geometry-msgs sensor-msgs tf" S = "${WORKDIR}/git" inherit catkin
Now let's build it.
$ devtool build vectornav
Success !
Recipetool Integration
As "devtool add" failed to create a functional recipe but the above steps follow a set process, there is scope for extending recipetool to support ROS modules.
- Detect ROS module by checking for package.xml in root of source with tag buildtool_depend set to catkin
- Create basis of recipe in similar way to cmake (execluding inherit cmake
- Follow mapping in package.xml mapping table
Start with existing recipetool code, get smart with python3 and good luck!