Siemens S7-300 MPI to OPC server connection

Pete_S

Member
Join Date
Mar 2015
Location
Portland Maine
Posts
76
Hello All,

I am having trouble setting up a S7-300 MPI connection using Simatic Manager 5.5. I am trying to use an OPC server with a S7 MPI driver to read data from the PLC. I have an S7-300 that has a valid MPI connection configuration but that controller does not have any data blocks configured. After too much time beating my head against my desk I decided to reach out for help. Can someone help me with steps required to pull running configuration on MPI configured PLC into Simatic manager so I can add a add a data block or configure from the ground up? I have experience with AB, GE and DirectSoft products but Siemens is really giving me a run for my money. Thanks!
 
Hi,

you can first try to read marker/flag values. They are always there, even without any program in the plc.
The basic setup for accessing a S7 via MPI is the MPI address of the CPU and the rack/slot combination. This is the position of the CPU in the S7 rack. A S7-300 has always a rack/slot combination of 0/2. With a S7-400 there are other combinations possible, as you can place the CPU on a position you want, or you can have multiple CPUs is one rack.

Who is the vendor of your OPC server? The item namings differ always a little bit between them.
 
Hi,

you can first try to read marker/flag values. They are always there, even without any program in the plc.
The basic setup for accessing a S7 via MPI is the MPI address of the CPU and the rack/slot combination. This is the position of the CPU in the S7 rack. A S7-300 has always a rack/slot combination of 0/2. With a S7-400 there are other combinations possible, as you can place the CPU on a position you want, or you can have multiple CPUs is one rack.

Who is the vendor of your OPC server? The item namings differ always a little bit between them.

Hi Thomas_v2,

Thanks for your swift reply. I am trying to resolve an issue with Proficy OPC server running on a Quickpanel+ where floats in a data block can not be read. I have successfully created a project from scratch for my CPU315-2 PN/DP controller that has a data block with a few floats in it. I can successfully connect to controller using Kepware S7-300 Ethernet driver and read/write to floats in my data block. However when I connect null modem serial cable to MPI adapter and Quickpanel+ I am not able to get good quality on any known tags such my DB floats or other generic registers as you referenced.
I am confident that I am missing something in my object configuration in Step 7 as I have an older CPU315-2 DP controller that the MPI was originally connected to with a program running and I am able to connect the Proficy server running on the panel and connect to known registers, but no data blocks are on that controller and I don't have backup for that controller.
So I see 2 ways to resolve, and I am stuck on both:
1: find the MPI configuration "gotcha" in my CPU315-2 PN/DP config so I can connect to the server on the panel
2: find a way to preform blind upload from CPU315-2 DP controller. When i set PN/PG interface to either PC (auto) or PC (MPI) and attempt to upload I get an error that the connection link can not be configured or is broken respectively. That controller does not have an Ethernet port, and although I have a Simatic NET 343 module in the rack it appears that it is not possible to upload from that module.
Any advice would be greatly appreciated!
 
Maybe someone has changed the MPI baudrate, for any reason.
The default baudrate is 187.5 kbit/s. I would try all available baudrates, and use the "show reachable partners" dialog from the Step 7 manager, as it should show you the CPU even if it has a different MPI address as configured.
 

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