MyActuator RMD X-series CAN driver SDK

Author: Tobit Flatscher (2023 - 2024)

0. Overview

This repository holds a CAN driver software development kit (SDK) for the MyActuator RMD X actuator series written in modern C++17 using Linux’s SocketCAN. The driver SDK is also exposed to Python through Python bindings generated with pybind11.

For the ros2_control integration please refer to this repository.

1. Installation

This driver SDK requires the following dependencies to be installed. For Debian Linux they can be installed through apt as follows:

$ sudo apt-get install -y build-essential cmake
$ sudo apt-get install -y can-utils iproute2 linux-modules-extra-$(uname -r)

In case you want to use the Python bindings you will have to additionally install Python 3, pip and pybind11:

$ sudo apt-get install -y python3 python3-pip python3-pybind11

After having installed its dependencies you will have to install the driver SDK either as a C++ library or Python package as described in the following steps. Both will use CMake to compile the C++ code.

1.1 Building the C++ library

For building the C++ driver SDK open a new terminal inside this folder and execute the following commands. On older versions of Linux the build might fail with the error message error: 'const struct can_frame' has no member named 'len' and you will have to apply the code modification discussed in issue #5.

$ mkdir build
$ cd build
$ cmake .. -D PYTHON_BINDINGS=on
$ make -j $(nproc)
$ sudo make install

The flag PYTHON_BINDINGS (defaults to off) builds the Python bindings additionally to the C++ library. In case you are only interested in using the C++ library feel free to leave it off. When building the Python bindings like this they will be compiled to a shared library but not be installed. This means you will either have to install the library manually or you will only be able to import them locally inside the build folder.

For uninstalling the package again you can use the following command $ xargs rm < install_manifest.txt.

1.2 Installing Python package

For building and installing the Python bindings for this SDK open a new terminal inside the main folder and execute the following command:

$ pip3 install .

This will use the setup.py to invoke CMake and install the bindings as a C++ library. If you want to remove them again simply invoke $ pip3 uninstall myactuator-rmd-py.

1.3 Building with ROS 2

For building and installing this package with ROS 2 open a new terminal on then top-level folder of your Colcon workspace (e.g. colcon_ws) and execute the following command:

$ colcon build --cmake-args -D PYTHON_BINDINGS=on -D BUILD_TESTING=on

where the two flags following --cmake-args are optional.

2. Using the C++ library

In case Ament is installed on your system but you want to install the package with CMake only, please make sure that your ROS 2 workspace was not sourced before running the installation.

In your CMake package you can then find the package and link to it as follows:

cmake_minimum_required(VERSION 3.20)
project(your_project)

find_package(myactuator_rmd REQUIRED)

add_executable(your_node
  src/main.cpp
)
target_compile_features(your_node PUBLIC
  cxx_std_17
)
target_link_libraries(your_node PUBLIC
  myactuator_rmd::myactuator_rmd
)

A minimal example for the main.cpp can be found below:

#include <cstdlib>
#include <iostream>

#include <myactuator_rmd/myactuator_rmd.hpp>


int main() {
  myactuator_rmd::CanDriver driver {"can0"};
  myactuator_rmd::ActuatorInterface actuator {driver, 1};

  std::cout << actuator.getVersionDate() << std::endl;
  std::cout << actuator.sendPositionAbsoluteSetpoint(180.0, 500.0) << std::endl;
  actuator.shutdownMotor();
  return EXIT_SUCCESS;
}

3. Using the Python bindings

Load the library and continue to create a driver for a particular network interface (here can0) and drive (here 1 corresponding to the CAN-address 0x140 + 1 = 0x141) and control it through the Python API as shown below:

$ python3
Python 3.10.6 (main, Mar 10 2023, 10:55:28) [GCC 11.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import myactuator_rmd_py as rmd
>>> driver = rmd.CanDriver("can0")
>>> actuator = rmd.ActuatorInterface(driver, 1)
>>> actuator.getVersionDate()
2023020601
>>> actuator.sendPositionAbsoluteSetpoint(180.0, 500.0)
temperature: 19, current: 0.1, shaft speed: 1, shaft angle: 0
>>> actuator.shutdownMotor()

In case you installed the package through ROS 2 the shared library will be located inside the myactuator_rmd package. Therefore you will need to import it with import myactuator_rmd.myactuator_rmd_py as rmd.

For more information you might also inspect the contents of the module inside Python 3 with help(myactuator_rmd_py).

4. Automated tests

For testing you will have to install the following additional dependencies

$ sudo apt-get install -y libboost-all-dev libgmock-dev libgtest-dev

The tests can then be build by passing the additional flag -D BUILD_TESTING=on to CMake. After building the driver SDK with the additional flag you will have to bring the virtual CAN interface up with:

$ sudo modprobe vcan
$ sudo ip link add dev vcan_test type vcan
$ sudo ip link set up vcan_test

Additionally there is a CMake flag SETUP_TEST_IFNAME that - if set to on - automatically sets up the virtual CAN interface for you but this requires the following command to be run as sudo. Finally for coverage reports with GCC you might use the flag ENABLE_COVERAGE but this will compile the code without optimizations.

Finally you can launch all the tests with the following command:

$ ctest