The MPI protocol specifications

Does anybody know where I can find the protocol specifications for MPI? Or is that one of Siemens' closely kept trade secret?

Some manufacturers of DDE server software and SCADA packages seem to have been able to buy that info. The price has never been mentioned, but I figure it has been a large number.

Kind regards,

If you can follow programs written in 'C' you could study the libnodave library for Siemens, it covers the MPI protocol amongst others. The source code is included in the download. The man behind libnodave reverse engineered the MPI protocols by watching the data exchanged across the interface.

http://libnodave.sourceforge.net/

If your purpose is just to use the MPI interface then you would probably be better to let libnodave do the 'nitty gritty' which leaves you free to concentrate on the higher level programming.

Remember that if you are a bit of a brain box and can add something to the project, then post it back so that it becomes part of the project.

I dont think that the actual sourcecode to the MPI protocol itself can be found in Libnodave, or any of the 3rd party S7 comms libraries.
They all communicate via MPI by going via an adapter. It is the communication to the adapter that Libnodave and the 3rd party comms libraries covers.

Apart from that, I think that it will be somewhat a waste of time to study MPI.
In stead look intocommunicating with S7 via ethernet which is also in Libnodave. And this is directly to the S7 CPU or CP without the need for an adapter.

Learn something new every day, I thought the MPI adapters were just simple devices but these guys agree with Jesper
http://modbus.control.com/thread/1026157849

In the spirit of learning I did a quick bit of Googling and thought I had struck gold for you.
http://www.runmode.com/usefulstuff.html
but he has removed his MPI info and instead directs you to libnodave.

Then I found this information:
http://cnczone.com/forums/general_electronics_discussion/48705-pc-mpi_adapter.html#post379814
that gives the RS232 to S5 connector (and maybe S7) as a simple R232 to 4-20mA loop signal converter. Which puts back to not being sure about any of it. But what the heck, if 'Heisenberg' can have uncertainty then I am in good company.

Just found a different program to communicate with S7300 & 400:
http://s7net.codeplex.com/

From what I can find by using Google translate it is simpler to use and understand than libnodave. However it is only available in C#.net

BryanG said:

Then I found this information:
http://cnczone.com/forums/general_electronics_discussion/48705-pc-mpi_adapter.html#post379814
that gives the RS232 to S5 connector (and maybe S7) as a simple R232 to 4-20mA loop signal converter.

Click to expand...

No, not for S7.
This "RS232 to S5 connector" is a RS232 level to TTY level converter. The AS511 protocol for S5 is much simpler and much much slower than MPI. That is why you can connect to a normal RS232 port on a PC. Cannot be compared with MPI.

I second this:

JesperMP said:

Apart from that, I think that it will be somewhat a waste of time to study MPI.
In stead look intocommunicating with S7 via ethernet which is also in Libnodave. And this is directly to the S7 CPU or CP without the need for an adapter.

Click to expand...

MPI is slloooowwww and expensive. Are there MPI hubs? I have Ethernet switches and USB hubs.

I have an extreme dislike for any network that doesn't easily connect to a laptop. That limits my current choices to Etherent and USB.

I wonder if Thunderbolt will catch on.
http://www.apple.com/thunderbolt/
http://www.intel.com/technology/io/thunderbolt/index.htm
10 Gbps. Wow.