Guide

This guide will solve your problem of where to start with documentation, by providing a basic explanation of how to do it easily. Look how easy it is to use:

  • After you catkin_make the project, in one terminal run:

$ roslaunch ether_ros ether_ros.launch

  • After that, and while the process is running, you run in another terminal:

$ rosrun ether_ros ethercat_keyboard_controller.py

  • Now you can give orders to the EtherCAT Communicator via a custom terminal.

Have fun playing around!

  • Tip: You could run a bash script in the custom terminal by running:

[ethercat_controller] > !r my_awesome_bash_script.sh

Notice that your script must be under the scripts directory. You could also check some example scripts there.

Features

  • Real time characteristics, using PREEMPT_RT patch
  • EtherCAT technology adaptation in Linux
  • Works in a recent version of ROS (kinetic)
  • Utilizes the main development framework for EtherCAT applications, IgH Master kernel module

Installation

SUPER SOS : The following manual will be extremely helpful for understanding the instructions given in this section. You should definitely read it before procceding. Link.

0. Preempt_RT Patch

First step to utilize the repository given, is to install the preempt_rt patch in the kernel. Note that in order to install the IgHM, the kernel should be up to 4.9. A proper guide for the installation procedure can be found in the following link. After you patch the kernel (say 4.9), you will want to use some other configuration parameters in the build of the kernel. Therefore after step 3 and in the line of make menuconfig of the previous link, you will want to specify some extra configuration parameters, derived from the chapter 3 of the manual mentioned in the beginning, namely:

  • CONFIG_PREEMPT_RT_FULL
  • CONFIG_CPU_FREQ=n
  • CONFIG_CPU_IDLE=n
  • CONFIG_NO_HZ_FULL=y
  • CONFIG_RCU_NOCB_CPU=y

The author has used only the first configuration parameter and has seen great boost in the performance of the real-time tasks specified. Future work requires more tweaks to be done, derived from the afore mentioned manual.

Tip: While you are in the menuconfig, type “/” and you can type to find the place of a configuration parameter. Exit with ESC

1. Installation of IgHM

  1. cd into the etherlab-mercurial folder
  2. Run make ethercatMasterInstallWithAutoStart. Note that root access is needed. If you use another native driver from e1000e, open the Makefile and change the configure option with your driver version. You can find here and here (Chapter 9), the supported hardware and the options the command configure takes, respectively. If your hardware is not supported or if you don’t want the native driver support fuzz, then you should change the configure command to enable generic driver support (although I think it defaults to that).

2. Run the scripts

  1. Because we want to have a process in realtime context, we should change it’s priority (done in the code -FIFO policy, 80 priority-). Besides that, the interrupt handler which handles the interrupts generated by the network driver, should have higher priority than the process we develop, so that the EtherCAT datagrams are ready to be sent/received before we process them. For that cause I have written a script, as a sample script, to change the priority of the irq process of the network card.This should be used accordingly to change your process’s priority. You could check if the priority has changed with the chrt command. How-to can be found here.
  2. Aside from the enhancements proposed by the manual, we should also change the throttling of our network driver to 0. This is done in the script also in the testbench directory. It is based on my e1000e driver, so use it as a sample script. Documentation for the insertion of the module of the e1000e network driver can be found here.
  3. Run the script for changing the permissions of ether_ros. We set the suid of ether_ros to be root, so that the ether_ros can be launched without sudo. This will be useful after you catkin_make the project.

Limitations / Steps Forward

This program assumes that the actual control code of the robot is running in the EtherCAT slaves. Therefore there is no connection between this program and ros_control, although the intention of the author is to make this connection happen, for robots that do have a control api inside ROS. This of course means that the ros_control module should communicate afterwards with this program, to send new data to the EtherCAT slaves. Needless to say, the EtherCAT slaves will have a much more passive role in this configuration.

Support

If you are having issues, please let us know. We don’t have a mailing list yet, so the default way is by communicating with: mkaramousadakis@zoho.eu

License

The project is licensed under the GPLv2 licence. See more details in the source files of the project or in the Lincence section.