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This example provides a library of LabVIEW VI's that can be used to communicate with a Siemens S7-300 PLC via an Ethernet port over TCP/IP.
This example communicates with a S7-300 series PLC through Ethernet TCP/IP - no adapter is needed. The example provides an API to read from / write to registers on the PLC.
To my knowledge, Siemens has never released the details of the S7 protocol. Much of what is publicly available on S7 is based on observations of the protocol by others. There is an open source S7 data exchange package available at http://libnodave.sourceforge.net/ that documents many S7 features.
The example contains two top-level VIs: S7Com_Once.vi and S7Com_W+R_Loop.vi.
1.S7Com_Once.vi performs one read or write per execution. It writes to the target PLC from an array of I32, it reads from the target PLC into an array of I32. The number of bytes written is proportional to the number of elements in the array to be written and the transport size parameter.
2.S7Com_W+R_Loop.vi regularly writes to and reads from a pair of DBs in the target PLC. In order to use it, your Step7 PLC project should provide two Data Blocks, DB11 and DB12. See the screen capture image db11&12.PNG for their layout. After downloading the DBs to your PLC, monitor and change DB VAlues with a VAT. As can be seen in the VI, the transfer size is DWORD.
3. For more information, refer to the Read Me included in the download.
LabVIEW 8.5 or Later
Siemens S7 TCP v3_3 LV 8_5.zip
This code is setup to be fault tolerant; i.e. - if a cable is disconnected or connection is lost the "S7_Error_Reconnect.vi" can be called to cleanup the bad connection and re-open a good connection. There are some optimizations for reading multiple registers from a single DB block.This code is derived from the Serial MPI S7 Protocol Exaple
This code was provided by a fellow developer (thanks!) and uses a slightly different architecture.
Note - the attached files are experimental VIs provided for educational purposes only. No warrantee is expressed or implied. You should test your code and completely understand the implications of writing to or reading from an operating PLC.
**This document has been updated to meet the current required format for the NI Code Exchange. For more details visit this discussion thread**
Example code from the Example Code Exchange in the NI Community is licensed with the MIT license.