Profibus Newbie Questions

I'm working with a Siemens-based machine that uses Profibus to link the S7-300 (CPU315-2 DP) rack with remote I/O, drives, and a Multipanel 270 Series.

I have been tasked to integrate a Siemens Microbox 420 into this system. The Microbox will send/receive data to/from the CPU315 via a Visual Basic 6 application.

My VB6 application will send 100 bytes and receive 300 bytes.

I want to get communicating as cheaply as possible (of course), so I am looking into Libnodave or any other DLL solutions available. The OPC servers are nice but too much for the scope of this project.

My questions/uncertainties:

Since the Microbox will be on the Profibus network, is it required to use the DP protocol, or can different protocols (i.e. S7) co-exist?

Is the Multipanel considered a DP Master? Will the Microbox be a DP Master? If both are masters, is this allowed?

What is the most economical way to get data between the Microbox and CPU315-2 DP?

mfoxips

Since the Microbox will be on the Profibus network, is it required to use the DP protocol, or can different protocols (i.e. S7) co-exist?

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S7 can be used. It is most typical to use the S7 protocol for your kind of application.

Is the Multipanel considered a DP Master?

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Yes.

Will the Microbox be a DP Master?

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It is the most common.

If both are masters, is this allowed?

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Yes. It is called "multimaster".

What is the most economical way to get data between the Microbox and CPU315-2 DP?

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If there is allready a DP port on the microbox, then go for DP. Otherwise go for ethernet.
For ethernet you will at least require a CP343-1 LEAN in the S7-300 "rack." And then you need Libnodave or Simatic Softnet Lean.

As there is remote i/o and drives via DP, then the presence of additional masters slows down the network considerably. "mono-master" is approximately 5-10 times faster than "multi-master". Consider to put the MP panel and the microbox on ethernet. I generally dislike mixing remote i/o networks and supervisory/hmi networks, never mind that it is possible with profibus.


For program development, If I were you, then I would go for the OPC server + an OPC wrapper for VB. To go for libnodave will require more work, but is certainly doable.
Automation is expensive, realise it. The reason is that "it must work reliably" has top priority, "it must be maintainable" has second priority, "it must be cheap" comes way down in the priority list.
Consider libnodave, but dont focus too much on initial low cost.

Thanks for the reply JesperMP. I too would prefer the operator interfaces on Ethernet and the control on Profibus DP; Unfortunately, the customer (OEM) is pushing the Profibus Microbox. By the way, the Microbox has an integrated Fieldbus port. I believe it's a mini CP5611 (via Siemens TSC).

Regarding the driver (OPC vs. Libnodave), I need to have all my options available due to budgetary constraints. If money wasn't a concern, I would already have Simatic Net DP. I have used the Simatic Net IE Lean package with good results.

So, if I understand correctly, I have two scenarios:

All devices (CPU, MP270, Microbox, Rem I/O, Drives) on Profibus Network communicating DP

Microbox running Simatic Net DP or equivalent


OR


CPU Connection 1 communicating DP with MP270, I/O, and Drives
CPU Connection 2 communicating S7 with Microbox

Microbox running one of the following:

Simatic Net S7 or equivalent
Libnodave


Any comments are welcome.

There is another option : if I am not mistaken , the microbox can also be setup to use MPI and you could then connect to the PLC via MPI , you would have no extra loading on your DP network and can still use the libnodave.

On the other side with a ethernet lean module in the PLC you can use VB to communicate via sockets ( using UDP or TCP ) you can program an array to receive and send info to the PLC .In the PLC you need to make a connection via netpro to your PC and use FC5 and FC6 for communications.I have used this using Delphi as programming language and works well.I also tried using Delphi and OPC .If all is well then comms are great but if there is a communication failure or OPC server failure then it fell on his backside.

Geetings Eric

mfoxips said:

All devices (CPU, MP270, Microbox, Rem I/O, Drives) on Profibus Network communicating DP
Microbox running Simatic Net DP or equivalent

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If I understand correctly, then you dont have the opportunity to switch the MP270 from DP to Ethernet. Also, MP270 uses S7 (=profibus master) rather than DP, you cannot change that either.
Therefore it is not a good idea to use DP (as a profibus slave) with the mcicrobox. You will get all the disadvantages and none of the advantages.

mfoxips said:

CPU Connection 1 communicating DP with MP270, I/O, and Drives
CPU Connection 2 communicating S7 with Microbox
Microbox running one of the following:
Simatic Net S7 or equivalent
Libnodave

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Again, the MP270 is really a profibus master with an S7 connection. Apart from that this looks like the way you are headed.

aikona said:

I have used this using Delphi as programming language and works well.I also tried using Delphi and OPC .If all is well then comms are great but if there is a communication failure or OPC server failure then it fell on his backside

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It is problems like that, that a shrinkwrapped solution shall take care of. Did you program the OPC stuff in Delphi yourself ? Or did you use a wrapper ? I hear good things about dOPC from Kassl for Delphi, but havent actually tried using it myself.

JesperMP said:

It is problems like that, that a shrinkwrapped solution shall take care of. Did you program the OPC stuff in Delphi yourself ? Or did you use a wrapper ? I hear good things about dOPC from Kassl for Delphi, but havent actually tried using it myself.

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Hi

I was asked to 'investigate' without the invest part ,various options for some future projects.So I got all the freebies and shareware together and started testing.
I started at http://www.opcconnect.com/delphi.php and played around with the software on offer.It works well if there are no errors or faults.To do all the error and fault processing you need to have good understanding of OPC ( and I don't have that) and you need to have a good understanding of window programming ( again ,not really my strong point).Eventually for 'real' projects ( read projects with money) we now use WinCC or WinCC flex.For one off and small projects I write some software in delphi and for some applications it works better than winCC.I did a SMS system with delphi .Two connections , one to the PLC using a UPD component,one to our telephone exchange using a TCP component.Basically if a production line stops for longer than 30 to 45 seconds without operator intervention then the PLC sends a machine code and error code to the PC and on the PC ,according to info in a database , sends an SMS to the operator .Something like 'Machine 5 product jam'.The SMS also get logged in a database ( MySQL cause its free) and you can get a good idea of long stoppages.Reading the info in the database we use a webserver ( apache) and PHP .

Greeting

Eric

Which one of the software solutions at opcconnect did you use then ?

If I had to make a home-grown HMI or datalogging solution myself, I would propably co with Delphi and then dOPC from Kassl. If I had many many similar projects that could justify the purchase, then I would possibly consider ACCON-AGlink S7 from Deltalogic. That license is a bit expensive, but on the other hand you dont have to pay per runtime.

I really recommend that you shop at reputable vendors. You get a finished product that will work from day one, support when you cannot figure it out, and very important - you can upgrade when new hardware and software versions appear (just think about Windows NT-2000-XP-Vista-??-??-??- etc.).

JesperMP said:

Which one of the software solutions at opcconnect did you use then ?

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I first used the 'simple opc client' and the libraries.Later I tried with the Siemens Net OPC .Also tried the software that came with an Applicom industrial ethernet card .

JesperMP said:

If I had to make a home-grown HMI or datalogging solution myself, I would propably co with Delphi and then dOPC from Kassl. If I had many many similar projects that could justify the purchase, then I would possibly consider ACCON-AGlink S7 from Deltalogic.

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If I had to get something besides Siemens I think I would try Matrikon or INAT

Eric

aikona said:

If I had to get something besides Siemens I think I would try Matrikon or INAT

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The reason why I mention Deltalogic as an alternative is that it is a DLL, not an OPC solution, so you get the program interface part and the driver part in ONE package. And also you can get a developer license in stead of having to buy single licenses everytime.
Matrikon for sure and also Inat i belive are both OPC that you have to purchase single licenses for.

I am missing the assertion that the MP270 is communicating S7 while a Profibus master. When I look at the Connection Setup in WinCC Flex, I see DP as the protocol.

So, if this is true, I can use any of the following software packages to establish communications between a Microbox 420 Fieldbus port and a CPU315-2 DP (DP port):

Softnet-DP
Softnet-S7
Libnodave

Thanks,
mfoxips

"DP" is often used to denote "Profibus". Much confusion comes from this.
For sure the MP270 is a Profibus master, but it does not communicate by DP master-slave communication, but by master-to-master communication
When stations communicate by master-slave it is some times also referred to as "DP", see below.
When a HMI talks to a PLC via Profibus master-to-master it is some times but not always referred to as "S7" communication.

Siemens sure know how to confuse people. I has taken me some time to find the way through this jungle myself. And I still dont know everything about this jungle.

Softnet-DP is meant for Profibus master-slave communication. You dont want your OPC server to communicate in this way unless there are some special reasons for it !

Softnet-S7 is meant for MPI or Profibus master-to-master communication.
This is the typical variant for an OPC connection to a PC for datalogging or HMI purposes. This is the one you need.

Libnodave also uses MPI or Profibus master-to-master communication.
To use the built-in CP5611 in the Microbox, I think that libnodave needs some additional Siemens drivers. If you used ethernet, then Libnodave could work on its own.

Keep asking.

I think the OEM I'm working with is in the same jungle.

They assert that the only master on the network is the CPU315-2DP. Yet the WinCC Flex Connection Setup shows the HMI as the "Only master on the bus".

I believe you have just asserted that both the CPU and the MP270 are masters.

And I have just slipped into the "quicksand" of ignorance...