I am completely new for EtherCAT. And I am looking for a good starting point to study EtherCAT master.
I found that there is a great open source implementation called SOEM.
But without any background of EtherCAT, it is really hard to understand the code.
Could anybody help me to find the way studying EtherCAT master?
To start you need to understand the technology before you can dive into the master. I'd recommend the following three resources.
EtherCAT Technology (Section I)
This is an overview of the technology and definitely where you want to start.
EtherCAT Registers (Section II)
This is a dry read, but a good reference to understand the different registers that are used to communicate between an EtherCAT master and slave.
ET1100 Hardware Data Sheet
Even drier, but this is a datasheet for a common ASIC for building an EtherCAT slave. It can help you understand even more detail about the communication between an EtherCAT master and slave.
To properly implement an EtherCAT master is no easy task and requires a lot of reading. There is more documentation available but it requires a membership to the EtherCAT Technology Group. That's where you can get access to more technical information.
Another EtherCAT master open source project, that I'm familiar with, is IgH
The best way to go through EtherCAT master is IgH website
http://etherlab.org/en/ethercat/index.php
They also have the source code for the etherCAT master and other software components. download the zip in linux and enjoy EtherCAT
Related
Iam looking at software that opens up a data set and grabs a list of server ips and pings them. Someone familar with this software packge says there is nothing else faster because the software is built on C++. Short of rebuilding the app in java is these anyway i can confirm what is the best language when building an app around snmp?
I know the question of C performance is posted all over the place but I do not see anything related to SNMP. When your core application is somthing like snmp is there a prefered programing lang?
The performance of an SNMP client isn't likely to have much to do with the implementation language. The network and the responsiveness of the server are the rate-determining steps.
I did my best to search all topics regarding to SCADA and developing your own C++ desktop application to communicate with PLCs, but could not find any recent, or in my opinion, relevant topics that fit what I needed. If I missed them, a link to them would be very much appreciated. If I also happened to post this in the wrong section, or you can think of a better section for me to post this in, I will take it there.
With that said, I thank you in advance for taking the time to read my questions, and appreciate any input you have to offer.
A little bit about what I'm doing
I'm currently in school for electromechanical engineering, and for my final year project I am developing a desktop application in C++ to monitor PLCs we have located within one of our labs.
Within this lab, I have a pre-existing ethernet network connecting all PLCs to single point, which I am tying into with a PC, and will be doing all my work from there.
I will be developing the application in Qt for an easy way to design the GUI, and giving me access to the QNetworkInterface as well as QTcpSocket.
With that said, I wouldn't go as far as saying I'm an experienced programmer, but I have been fooling around with a few languages (i.e.: python, c++, c, php) for quite a few years, and am still learning, considering the learning NEVER stops.
My questions
Is there any reference material I can read, that you can suggest, on the subject to more easily understand what sort of process I need to go through to receive information (i.e.: individual I/Os, status bits, tags, logs, etc...) from the PLCs directly, and not through an OPC server?
If an OPC server is required, I've never dealt with OPC links other than using Rockwell Automations RSLinx to grab tags and display their values within excel (I had created a prototype using that exact method to start, but would like to move away from excel, and if possible, the OPC server (RSLinx) as well). What would you suggest to someone who knows nothing about the subject of OPC servers, or to my knowledge, OPC in general?
Have any of you previously written your own application to do something similar, if not of the same nature to what I'm trying to accomplish?
What advice or suggestions would you give for someone who is attempting this type of project?
PS: As a start for this project, I would initially just want to get the reading of the I/Os (tags or addresses) to view what their current values are (closed or open for inputs, energized or not for outputs). But eventually I would also like to be able to write values to tags on the PLCs I'm monitoring based on the values I've received from them.
PSS: I would like to note again, that I am still a student, and am still learning about this subject in it's entirety. I would just like to ask for your patience, as I may not grasp things completely the first time!
If I've missed any information you feel is pertinent to be able to provide an answer, please let me know! I will do my best to come up with said information in a timely manner!
Thank you!
EDIT #1: Added in another question, and altered my first question slightly
EDIT #2: Fixed up question 2
IMHO a SCADA program should have as a minimum requirement to be able to connect to an OPC server. OPC is used for most commercial PLCs.
Strictly speaking there is no need to have an OPC server/client approach but it gives you flexibility and gives you an abstraction model. If you want to directly connect to PLCs using a protocol then that is of course possible as well. You then need to know more details about the protocols and their various versions.
Yes I worked for a few years in a team that developed a commercial SCADA application.
It is very easy to get lost in details in such a project so try to keep things as simple as possible. By using OPC you will save time instead of fiddling directly with the protocols. You could add the ability to add custom-drivers for other protocols - depending on your timeframe. Try to model up your project before you start coding to a birdsview of the model and avoid getting lost in the details.
I would stay well away from looking to write your own code to connect directly
to an AB PLC - there are products out there that you can use in your application:
http://www.rtaautomation.com/software/ethernetip/client/tagc/ControlWin.html
http://www.automatedsolutions.com/products/dotnet/ascomm/
You would be better to use OPC - you can write you own OPC client if you want and follow examples you find here:
http://www.opcconnect.com/source.php#freesource
According to this http://www.control.com/thread/1026173407 you should be able to get source code of Kepwares OPC Quick Client.
It would probably be easier to just use a library as in this example (RSLogix,C#):
http://www.mesta-automation.com/opc-client-with-c-an-how-to-video/
You might find this of use:
http://www.rockwellautomation.co.kr/applications/gs/ap/GSKR.nsf/files/rslinxsdk_ma_eng.pdf/$file/rslinxsdk_ma_eng.pdf
Some resources:
http://www.opcconnect.com/ ,
http://www.mesta-automation.com/
Answer to question #4 - realize that your lab technically could contain ANY manufacturer's PLCs in the future. If you ever took a Data Communications class, you realize that for N different PLC types, you would have to write N different communication drivers for your PLC client.
This is where standards are helpful. Without the use of a standard protocol, scaling your lab could become more time consuming and less manageable. This is why communications standards exist.
HOWEVER, not all PLCs necessarily support the standard(s) you may decide upon.
The best choice is OPC/UA. Many PLCs have server drivers readily available. That means that your client just needs to understand 1 protocol (OPC/UA), and then it can "easily" be connected to any PLC that has a driver for that standard.
After that, there is OPC. After that, Modbus (TCP and RTU flavors), a relatively simple industry standard that is supported by most PLCs. EtherNet/IP is also a possible choice, although not all PLCs support it in a "server" role (many do support it as a client, but that is not what you need).
have a look at pycomm in github or pylogix at github which are Python written drivers to link to clx plc.
I am going to develop a cloud application and in my research for state of the art tools in Cloud Computing i saw some references to OCCI (Open Cloud Computing Interface).
I was not able to find out an answer to the following questions
1)Is it easy to use this Interface ?
2)What programming languages does this interface Supports ?
3)Is this Interface mature enough?
Any information are well appreciated!
This question has been asked quite some time ago but, hopefully, the answer is still relevant.
Is it easy to use?
Depends on what you want. If you want to make your own implementation, then probably not. If you use one of the existing implementations (see bellow), then yes.
What programming languages does this interface Support?
We know about two implementations (libraries, CLI), which are for Ruby and Java. See:
https://wiki.egi.eu/wiki/rOCCI:ROCCI
https://github.com/EGI-FCTF/jOCCI-api
rOCCI (the first one) also as a server side (the rOCCI-server) that translates OCCI to propriatary cloud management platforms such as OpenNebula.
Is this Interface mature enough?
Yes, given that it is being used by real-world infrastructures. Among them, e.g., the EGI Federated Cloud. That said, the current OCCI specification (1.1) has a few shortcomings that will be addressed in version 1.2 (due in Autumn 2015), so that if someone is just starting a project, it is worth implementing with 1.2 already.
Many of your questions can be answered (positively, by the way!) by visiting the OCCI-WG home site at http://occi-wg.org and/or searching on "occi implementation".
Another recent and useful resource is the tutorials and workshop talks given at the recent Cloud Interoperability Week held simultaneously with events in Madrid and Santa Clara, part of the Cloud Plugfest hands-on developer training series:
Or generally at http://www.cloudplugfest.org/
The basic specs are published by the Open Grid Forum.
The Open Cloud Computing Interface (OCCI) is a set of specifications delivered through the Open Grid Forum, for cloud computing service providers. OCCI has a set of implementations that act as proofs of concept. It builds upon World Wide Web fundamentals by using the Representational State Transfer (REST) approach for interacting with services.
I'm trying to write up a tool that requires knowledge of the state of other machines in a cluster (local LAN). This is for a network failover/high availability system similar to VRRP and corosync/openais, but I wish to contain more information (such as near real-time speed/performance characteristics) so devices can make more intelligent choices. This means using a protocol more complicated than a predetermine weight-based mechanism: by allowing all clustered machines to see the state of each other, they can communally agree on which is the most suitable to be the master device.
From my searches, I haven't found any (C, C++ or JavaME) libraries that offer a distributed state mechanism. Ideally, I'm looking for something that broadcasts/multicasts each individual machines state periodically so participating machines can build up a global state table and all can see who the master should be. State in this case is arbitrary key/value pairs.
I'd rather not re-invent any wheels so am curious to know if anyone here can point me in the right direction?
If I were you I'd investigate memcached (memcached.org) or one of the nosql variants.
It sounds like Apache ZooKeeper might be a good match. It's distributed, hierarchical key-value store. To quote their Overview page:
ZooKeeper was designed to store coordination data: status information, configuration, location information, etc.
Here's an example of a simple Leader Election recipie, although it would require adaptation to determine a leader by some weighted criterion.
I'm not sure if there is any application for your purpose or not.
But I know that you can write a simple program with MPI library and broadcast any information that you want.
all client's can send their state to root node, and the root node then broadcast the message.
functions that you need for this are:
MPI_Bcast
MPI_Send
MPI_Recv
there is lots of tutorial on C++/MPI on net, just google it!
I am designing scalable PPP [mean it can be extended to over Ethernet, over HDLC, over ATM etc.]. I was stuck in determining whether State Machine is hadle by PPP stack [means i have design Base class for PPPStack in which FSM, encode, decode etc is there] or PPPoE [which is derived from my PPP Base Class PPPStack].
I am designing PPP using C++, so that it can be extended to oE, oATM etc.
PPP frame encoding in done in PPP itself and PPPoE [of which PPP frame is add after discovery and start of session].
This is first time i am writing Scalable, If anybody involved in Scalable Architecture would love hear points from them too:)
Thank you so much in advance
PPP does have a state machine, several in fact. The link is started, authorized, and kept up by a state machine.
The LCP, link control protocol, however, is a much more complex state machine you'll need to deal with.
There are a lot of resources about PPP, and I'm afraid the only question I saw in your post was
"I was stuck in determing wheter State Machine is hadle by PPP stack or PPPoE."
The answer is PPP does have several state machines.
PPPoE might also have another state machine or two, but I haven't checked into that.
Here are a few resources that might help you:
Very nice document with a good LCP state transition table:
http://scholar.lib.vt.edu/theses/available/etd-04252000-20310024/unrestricted/chapter4.pdf
Excellent powerpoint overview talking about many aspects of PPP:
http://www.cs.huji.ac.il/~sans/students_lectures/PPP-Intro.ppt
Also, a google search is likely to be useful:
http://www.google.com/search?q=ppp%20state%20machine
Good luck, and feel free to revise your question if I didn't understand it.
-Adam