Communication over an MPI subnet for Siemens S7


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I want to establish a communication between a Visual Basic application and a Siemens S7 314 over MPI. I'm using a converter from rs232 to mpi and my needs are to communicate with the plc and to realise a HMI application with VB.

I tried to use Simatic Net but i remarqued that all the softwares are destinated for Ethernet or Profibus communication. So what i can do??

thanks in advance for your help.

If you have already the 232/MPI converter, just use an opc server for this device. Systeme Helmholz ( has a server which can handle your converter and other devices if needed (TCP/MPI gateway, different MPI/Profibus cards, PPI cable and CP343). To an OPC Server is easy to talk to from a VB application.

Hope that helps.

Best regards,
Konni (konni(at)
easiest way is to buy the ProDave package from Siemens. This isn't too expensive and allows you to read/write PLC data directly from VB.

We've used it alot and it works well. The only problem is that it isn't very quick but for a simple SCADA type program in VB it should be fine as long as you don't need masses of data or need to spot changes in (lets say) 10ms cycles of the PLC.

Iain Smith
[email protected]