与西门子PLC通讯的Labview库，还不错

与西门子PLC通讯的Labview库，还不错。 以下是英文声明： Warning, 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. PLCs are often used to control hazardous processes and/or equipment. Writing to or reading from a PLC in active control of equipment or process can result in the disruption of the PLC program or data areas, potentially causing economic loss, property damage, generation or release of hazardous substances and/or personal injury up to and including death. Test your software in a controlled environment and qualify it before using it on active equipment or processes. 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. These VIs were based upon the example posted at http://decibel.ni.com/content/docs/DOC-5467. They were modified by observing and mimicking a S7 data exchange between a protocol converter and a S7-300 series PLC. The observations were accomplished with the wireshark network protocol analyzer, available at http://www.wireshark.org/ and the Wireshark Plugin f黵 S7-Protokoll, available at http://sps-forum.de/showthread.php?p=202763. The Address Area parameter determines which PLC memory area is the target for the reads and writes. I have only tested reads and writes to the Data Block (DB) Area. Your application should read and write to separate read and write DBs dedicated for transfer only. By confining reads and writes to dedicated Data Blocks, the risk of unintended overwrites may be reduced. The data type: S7Com_Transport_Size.ctl is a ring variable that contains the parameter for the size or type of the transfer. I have only had success with the BYTE, INT and DINT transport sizes on an S7-300 series PLC. The other sizes remain in the ring variable for testing on other PLCs. I do not know if the bytes of a multiple-byte variable are read or written atomically. The example contains two top-level VIs: S7Com_Once.vi and S7Com_W+R_Loop.vi. 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. 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. Included are example VIs (S7Com_to_PLC(SubVI).vi and S7Com_from_PLC(SubVI).vi) to map variables between Labview and the S7 PLC DBs. In the example, they use the same cluster type definition (S7Com_PLC_Data.ctl) but that is not a requirement. When you change the mappings, you must calculate the size of the variables to be read from the PLC in order to use the correct Read Length parameter. The read length parameter is in transport size units. The write length parameter is taken from the size of the write data array, so if the write data array is larger than you anticipate, data may be overwritten. The hex byte and hex byte array type definitions were created to format the internal data structures to show hex values so that they could be easily compared to the wireshark packet dumps. These VIs have been minimally tested on a NI 9072 cRIO. This is not finished. Needed are better error checking, cleaner S7 Response decoding, and stress testing with malformed data.