## repository: https://code.ros.org/svn/wg-ros-pkg
<<PackageHeader(pr2_etherCAT)>>
<<TOC(4)>>

(Now [[pr2_ethercat|pr2_ethercat]] in Hydro and later)

== Nodes ==
{{{
#!clearsilver CS/NodeAPI
node.0 {
  name=pr2_etherCAT
  desc=`pr2_etherCAT` is the node that executes the main loop for controlling the EtherCAT devices (including all motors) on the PR2.  It loads [[pr2_controller_manager]], which in turns loads and runs controllers that act directly on the robot's motors.  The ROS API detailed below is the interface for controlling `pr2_etherCAT` itself; as a result of loading the controllers, the `pr2_etherCAT` process offers a broader, and varying ROS API.  Superuser privileges are required to run `pr2_etherCAT`, to allow it to set its scheduling priority to run as a real-time process.  
  srv{
    0.name= pr2_etherCAT/reset_motors
    0.type= std_srvs/Empty
    0.desc= Reset the motors. This is required after a runstop is reset (by turning the red push-button on the back of the robot, or pressing the "Start" button on the wireless runstop), and after the motors have been halted via the `halt_motors` service.  Most often called from [[pr2_dashboard]].
    1.name= pr2_etherCAT/halt_motors
    1.type= std_srvs/Empty
    1.desc= Halt the motors.  To reset them, call `reset_motors`.  Most often called from [[pr2_dashboard]].
  }
}}}

==== Permissions ====
Running `pr2_etherCAT` requires the following "capabilities":
  * '''CAP_IPC_LOCK''' Lock memory (mlockall())
  * '''CAP_SYS_NICE''' Set real-time scheduling policies
  * '''CAP_NET_RAW''' Use raw sockets (for EtherCAT communications)
Superuser has these capabilities, but they can also be granted to another executable by setting file system attributes on the executable file.  The `pr2_grant` program is a setuid-root program which copies `pr2_etherCAT` to a part of the filesystem where attributes can be set (`/var/tmp`), and then grants the necessary capabilities to be able to run `pr2_etherCAT`.

==== Usage ====
{{{
Usage: ./pr2_etherCAT [options]
  Available options
    -i, --interface <interface> Connect to EtherCAT devices on this interface
    -x, --xml <file|param>      Load the robot description from this file or parameter name
    -u, --allow_unprogrammed    Allow control loop to run with unprogrammed devices
    -h, --help                  Print this message and exit
}}}

==== Example ====
`pr2_etherCAT` is usually executed from a launch file, such as [[pr2_bringup]]/pr2.launch.  Common configuration:
{{{
<node name="realtime_loop" machine="c1" launch-prefix="pr2_grant" pkg="pr2_etherCAT" type="pr2_etherCAT" args="-i ecat0 -x robot_description"/>
}}}

=== pr2_grant ===

`pr2_grant` is a utility that allows a regular user to run `pr2_etherCAT` with appropriate capabilities. See the section in `pr2_etherCAT` on "Permissions."


== reset_motors.py ==

`reset_motors.py` is a simple command-line script that calls the `pr2_ethercat/reset_motors` service.

{{{
$ rosrun pr2_etherCAT reset_motors.py
}}}

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