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Doc: Architecture, master module, system integration.

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Florian Pose 2008-07-04 09:24:19 +00:00
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documentation/ethercat_doc.tex
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@ -218,6 +218,8 @@ The list below gives a short summary of the master features.
\item Designed as a kernel module for Linux 2.6.
\item Implemented according to IEC 61158-12 \cite{dlspec} \cite{alspec}.
\item Comes with EtherCAT-capable drivers for several common Ethernet devices.
\begin{itemize}
@ -376,42 +378,40 @@ Figure~\ref{fig:arch} gives a general overview of the master architecture.
\paragraph{Master Module}
\index{Master module}
The EtherCAT master mainly consists of the master module, containing one or
more EtherCAT masters (section~\ref{sec:mastermod}), the ``Device Interface''
(section~\ref{sec:ecdev}) and the ``Realtime Interface''
(section~\ref{sec:ecrt}).
Kernel module containing one or more EtherCAT master instances (see
section~\ref{sec:mastermod}), the ``Device Interface'' (see
section~\ref{sec:ecdev}) and the ``Realtime Interface'' (see
section~\ref{sec:ecrt}).
\paragraph{Device Modules}
\index{Device modules}
Furthermore there are EtherCAT-capable network device driver
modules\index{Device modules}, that connect to the EtherCAT master via the
device interface. These modified network drivers can handle both network
devices used for EtherCAT operation and ``normal'' Ethernet devices. The
common case is, that the master module offers a single EtherCAT master: An
EtherCAT-capable network device driver module connects one network device to
this master, that is now able to send and receive EtherCAT frames, while all
other network devices handled by the network driver get connected to the
kernel's network stack as usual.
EtherCAT-capable Ethernet device driver modules\index{Device modules}, that
offer their devices to the EtherCAT master via the device interface (see
section~\ref{sec:ecdev}). These modified network drivers can handle network
devices used for EtherCAT operation and ``normal'' Ethernet devices in
parallel. A master can accept a certain device and then is able to send and
receive EtherCAT frames. Ethernet devices declined by the master module are
connected to the kernel's network stack as usual.
\paragraph{Application Modules}
\index{Application module}
An application module''\index{Application module} is a kernel module, that
uses the EtherCAT master (usually for cyclic exchange of process data with
EtherCAT slaves). These modules are not part of the EtherCAT master
code\footnote{Although there are some examples provided in the
\textit{examples} directory, see chapter~\ref{chapter:usage}}, but have to be
generated or written by the application engineer. An application module can
``request'' a master through the realtime interface (see
section~\ref{sec:ecrt}). If this succeeds, the module has the control over the
master: It can provide a bus configuration and exchange process data.
Kernel modules, that use the EtherCAT master (usually for cyclic exchange of
process data with EtherCAT slaves). These modules are not part of the EtherCAT
master code\footnote{Although there are some examples provided in the
\textit{examples} directory, see chapter~\ref{chapter:examples}}, but have to
be generated or written by the user. An application module can ``request'' a
master through the realtime interface (see section~\ref{sec:ecrt}). If this
succeeds, the module has the control over the master: It can provide a bus
configuration and exchange process data.
%------------------------------------------------------------------------------
\section{Phases}
\index{Master phases}
The EtherCAT master has several phases (see fig.~\ref{fig:phases}):
The EtherCAT master runs through several phases (see fig.~\ref{fig:phases}):
\begin{figure}[htbp]
\centering
@ -422,10 +422,11 @@ The EtherCAT master has several phases (see fig.~\ref{fig:phases}):
\begin{description}
\item[Orphaned phase]\index{Orphaned phase} This mode takes effect, when the
master has no Ethernet device connected. No bus communication is possible.
master still waits for its Ethernet device to connect. No bus communication is
possible until then.
\item[Idle phase]\index{Idle phase} takes effect when the master has an
Ethernet device connected, but is not requested by any application. The master
\item[Idle phase]\index{Idle phase} takes effect when the master has accepted
an Ethernet device, but is not requested by any application yet. The master
runs its state machine (see section~\ref{sec:fsm-master}), that automatically
scans the bus for slaves and executes pending operations from the user space
interface (for example Sdo access). The command-line tool can be used to access
@ -446,24 +447,37 @@ application that can provide a bus configuration and exchange process data.
%------------------------------------------------------------------------------
\section{The Master Module} % FIXME
\label{sec:mastermod}
\section{Master Module}
\label{sec:mastermodule}
\index{Master module}
The EtherCAT master is designed to run as a kernel module. Moreover
the master kernel module \textit{ec\_master} can handle multiple
masters at the same time: The number of masters has to be passed to
the module with the parameter \textit{ec\_master\_count}, that
defaults to $1$. A certain master can later be addressed by its index.
For example, if the master module has been loaded with the command
The EtherCAT master kernel module \textit{ec\_master} can contain multiple
master instances. Each master waits for a certain Ethernet device identified
by its MAC address\index{MAC address}. These addresses have to be specified on
module loading via the \textit{main\_devices} module parameter. The number of
master instances to initialize is taken from the number of MAC addresses
given.
\begin{lstlisting}[gobble=2]
# `\textbf{modprobe ec\_master ec\_master\_count=2}`
The below command loads the master module with a single master instance that
waits for the Ethernet device with the MAC address
\lstinline+00:0E:0C:DA:A2:20+. The master will be accessible via index $0$.
\begin{lstlisting}
# `\textbf{modprobe ec\_master main\_devices=00:0E:0C:DA:A2:20}`
\end{lstlisting}
the two masters can be addressed by their indices 0 and 1 respectively
(see figure~\ref{fig:masters}). This master index mandatory for
certain functions of the master interfaces.
MAC addresses for multiple masters have to be separated by commas:
\begin{lstlisting}
# `\textbf{modprobe ec\_master main\_devices=00:0E:0C:DA:A2:20,00:e0:81:71:d5:1c}`
\end{lstlisting}
The two masters can be addressed by their indices 0 and 1 respectively (see
figure~\ref{fig:masters}). The master index is needed for the
\lstinline+ecrt_master_request()+ function of the realtime interface (see
section~\ref{sec:ecrt}) and the \lstinline+--master+ option of the
\textit{ethercat} command-line tool (see section~\ref{sec:ethercat}), which
defaults to $0$.
\begin{figure}[htbp]
\centering
@ -472,26 +486,32 @@ certain functions of the master interfaces.
\label{fig:masters}
\end{figure}
\paragraph{Master Log Messages}
\paragraph{Init script}
\index{Init script}
The master module gives information about it's state and events via
the Syslog interface. The module loading command above should result
in the Syslog messages below (or similar):
Most probably you won't want to load the master module and the Ethernet driver
modules manually, but start the master as a service. See
section~\ref{sec:system} on how to do this.
\begin{lstlisting}[gobble=2]
EtherCAT: Master driver, 1.1 (stable) - rev. 513,
compiled by fp at Aug 09 2006 09:43:50
EtherCAT: Initializing 2 EtherCAT master(s)...
EtherCAT: Initializing master 0.
EtherCAT: Initializing master 1.
EtherCAT: Master driver initialized.
\paragraph{Syslog}
The master module outputs information about it's state and events to the
kernel ring buffer. These also end up in the system logs. The above module
loading command should result in the messages below:
\begin{lstlisting}
# `\textbf{dmesg | tail -2}`
EtherCAT: Master driver `\masterversion`
EtherCAT: 2 masters waiting for devices.
# `\textbf{tail -2 /var/log/messages}`
Jul 4 10:22:45 ethercat kernel: EtherCAT: Master driver `\masterversion`
Jul 4 10:22:45 ethercat kernel: EtherCAT: 2 masters waiting
for devices.
\end{lstlisting}
The master provides information about it's version number, subversion
revision number and compile information, like the date of compilation
and the user, who compiled. All messages are prefixed either with
\texttt{EtherCAT:}, \texttt{EtherCAT WARNING:} or \texttt{EtherCAT
ERROR:}, which makes searching the logs easier.
All EtherCAT master output is prefixed with \lstinline+EtherCAT+ which makes
searching the logs easier.
%------------------------------------------------------------------------------
@ -3348,42 +3368,54 @@ chapter~\ref{chapter:usage}).
\section{System Integration}
\label{sec:system}
To integrate the EtherCAT master into a running system, it has to be
guaranteed, that it is started on system startup. In addition, there has
to be a persistent configuration, that is also applied on startup.
To integrate the EtherCAT master as a service into a running system, it comes
with an init script and a sysconfig file, that are described below.
\subsubsection{The EtherCAT Init Script}
\subsection{Init Script}
\label{sec:init}
\index{Init script}
The EtherCAT master provides an ``init script'', that conforms to the
requirements of the ``Linux Standard Base'' (LSB\index{LSB},
\cite{lsb}). The script is installed to \textit{etc/init.d/ethercat}
below the installation prefix and has to be copied to the appropriate
location (see section~\ref{sec:make}), before the master can be
inserted as a service. The different Linux distributions offer
different ways to mark the service for starting and stopping in
certain runlevels (for example, SUSE Linux provides the
\textit{insserv} command).
The EtherCAT master init script conforms to the requirements of the ``Linux
Standard Base'' (LSB\index{LSB}, \cite{lsb}). The script is installed to
\textit{etc/init.d/ethercat} below the installation prefix and has to be copied
(or better: linked) to the appropriate location (see
section~\ref{sec:install}), before the master can be inserted as a service.
Please note, that the init script depends on the sysconfig file described
below.
To provide service dependencies (i.~e. which services have to be
started before) right inside the init script code, LSB defines a
special comment block. System tools can extract this information to
insert the EtherCAT init script at the correct place in the startup
sequence:
To provide service dependencies (i.~e. which services have to be started before
others) inside the init script code, LSB defines a special comment block.
System tools can extract this information to insert the EtherCAT init script at
the correct place in the startup sequence:
\begin{lstlisting}[gobble=2]
### BEGIN INIT INFO
# Provides: ethercat
# Required-Start: $local_fs $syslog $network
# Should-Start: $time
# Required-Stop: $local_fs $syslog $network
# Should-Stop: $time
# Default-Start: 3 5
# Default-Stop: 0 1 2 6
# Short-Description: EtherCAT master modules
# Description:
### END INIT INFO
\lstinputlisting[firstline=38,lastline=48]
{../script/init.d/ethercat}
\subsection{Sysconfig}
\label{sec:sysconfig}
\index{Sysconfig file}
For persistent configuration, the init script uses a sysconfig file installed
to \textit{etc/sysconfig/ethercat} (below the installation prefix), that is
mandatory for the init script. The sysconfig file contains all configuration
variables needed to operate one or more masters. The documentation is inside
the file and included below:
\lstinputlisting[numbers=left,firstline=9,basicstyle=\ttfamily\scriptsize]
{../script/sysconfig/ethercat}
\subsection{Service}
\label{sec:service}
\index{Service}
After the init script and the sysconfig file are placed into the right
location, the EtherCAT master can be inserted as a service. The different Linux
distributions offer different ways to mark a service for starting and stopping
in certain runlevels. For example, SUSE Linux provides the \textit{insserv}
command:
\begin{lstlisting}
# `\textbf{insserv ethercat}`
\end{lstlisting}
The init script can also be used for manually starting and stopping
@ -3396,45 +3428,6 @@ the EtherCAT master. It has to be executed with one of the parameters
Starting EtherCAT master done
\end{lstlisting}
\subsubsection{Sysconfig} % FIXME
\label{sec:sysconfig}
\index{Sysconfig file}
For persistent configuration, the init script uses a sysconfig file
installed to \textit{etc/sysconfig/ethercat} (below the installation
prefix), that is mandatory for the init script. The sysconfig file
contains all configuration variables needed to operate a master:
\begin{description}
\item[DEVICE\_INDEX] This variable must contain the PCI index of the
EtherCAT device. Setting this is mandatory for the EtherCAT init
script. Default: $-1$
\item[EOE\_INTERFACES] The number of virtual Ethernet-over-EtherCAT
interfaces, every master creates on startup. See
section~\ref{sec:eoeimp}. Default: $0$
\item[EOE\_BRIDGE] If this variable is set, all EoE interfaces will be
added to a network bridge according to IEEE 802.1D after master
startup. The variable must contain the name of the bridge. To use
this functionality, the kernel must be configured with the
CONFIG\_BRIDGE option and the \textit{bridge-utils} package must be
installed (i.~e. the \textit{brctl} command is needed).
\item[EOE\_IP\_ADDRESS] The IP address of the EoE bridge. Setting this
together with \$EOE\_IP\_NETMASK will let the local host communicate
with devices on the EoE bridge.
\item[EOE\_IP\_NETMASK] IP netmask of the EoE bridge.
\item[EOE\_EXTRA\_INTERFACES] The list of extra interfaces to include
in the EoE brid\-ge. Set this to interconnect the EoE bridge with
other local interfaces. If \$EOE\_\-BRIDGE is empty or undefined,
setting this variable has no effect. Important: The IP address of
the listed interfaces will be cleared. Setting
\$EOE\_\-IP\_\-ADDRESS and \$EOE\_IP\_NETMASK will re-enable them
for IP traffic.
\item[EOE\_GATEWAY] The IP address of the default gateway. If this
variable is set, the gateway will be renewed after bridge
installation. This is necessary, if the default gateway's interface
is one of the \$EOE\_EXTRA\_INTERFACES.
\end{description}
%------------------------------------------------------------------------------
\section{Monitoring and Debugging}
@ -3706,9 +3699,10 @@ This command will install the compiled kernel modules to
If the EtherCAT master shall be run as a service\footnote{Even if the EtherCAT
master shall not be loaded on system startup, the use of the init script is
recommended for manual (un-)loading.}, the init script and the sysconfig file
have to be copied (or linked) to the appropriate locations. The below example
is suitable for SUSE Linux. It may vary for other distributions.
recommended for manual (un-)loading.} (see section~\ref{sec:system}), the init
script and the sysconfig file have to be copied (or linked) to the appropriate
locations. The below example is suitable for SUSE Linux. It may vary for other
distributions.
\begin{lstlisting}[gobble=2]
# `\textbf{cd /opt/etherlab}`